Journal articles: 'Macadamia kernels'

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Richards, Tarran E., Wiebke Kämper, Stephen J. Trueman, Helen M. Wallace, Steven M. Ogbourne, Peter R. Brooks, Joel Nichols, and Shahla Hosseini Bai. "Relationships between Nut Size, Kernel Quality, Nutritional Composition and Levels of Outcrossing in Three Macadamia Cultivars." Plants 9, no. 2 (February 11, 2020): 228. http://dx.doi.org/10.3390/plants9020228.

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Tree nuts play an important role in healthy diets, but their economic value and nutritional quality may be affected by their size and paternity. We assessed relationships between nut size and kernel recovery, the incidence of whole kernels, fatty acid composition and mineral nutrient concentrations in three macadamia cultivars, “Daddow”, “816” and “A4”. We determined to what extent differences in nut size and quality were the result of different levels of cross- or self-paternity. Small nuts of all cultivars had lower kernel recovery than large nuts, and small nuts provided lower incidence of whole kernels in “Daddow” and “A4”. Small kernels had a lower relative abundance of the saturated fatty acid, palmitic acid, in all cultivars and higher relative abundance of the unsaturated fatty acid, oleic acid, in “Daddow” and “A4”. Small kernels had higher concentrations of many essential nutrients such as nitrogen and calcium, although potassium concentrations were lower in small kernels. Most nuts arose from cross-pollination. Therefore, nut size and kernel quality were not related to different levels of cross- and self-paternity. Identified cross-paternity was 88%, 78% and 90%, and identified self-paternity was 3%, 2% and 0%, for “Daddow”, “816” and “A4”, respectively. Small macadamia kernels are at least as nutritious as large macadamia kernels. High levels of cross-paternity confirmed that many macadamia cultivars are predominantly outcrossing. Macadamia growers may need to closely inter-plant cultivars and manage beehives to maximise cross-pollination.

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Nishijima, K. A., M. M. Wall, and M. S. Siderhurst. "Demonstrating Pathogenicity of Enterobacter cloacae on Macadamia and Identifying Associated Volatiles of Gray Kernel of Macadamia in Hawaii." Plant Disease 91, no. 10 (October 2007): 1221–28. http://dx.doi.org/10.1094/pdis-91-10-1221.

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Gray kernel is an important disease of macadamia (Macadamia integrifolia) that affects the quality of kernels, causing gray discoloration and a permeating, foul odor. Gray kernel symptoms were produced in raw, in-shell kernels of three cultivars of macadamia that were inoculated with strains of Enterobacter cloacae. Koch's postulates were fulfilled for three strains, demonstrating that E. cloacae is a causal agent of gray kernel. An inoculation protocol was developed to consistently reproduce gray kernel symptoms. Among the E. cloacae strains studied, macadamia strain LK 0802-3 and ginger strain B193-3 produced the highest incidences of disease (65 and 40%, respectively). The other macadamia strain, KN 04-2, produced gray kernel in 21.7% of inoculated nuts. Control treatments had 1.7% gray kernel symptoms. Some abiotic and biotic factors that affected incidence of gray kernel in inoculated kernels were identified. Volatiles of gray and nongray kernel samples also were analyzed. Ethanol and acetic acid were present in nongray and gray kernel samples, whereas volatiles from gray kernel samples included the additional compounds, 3-hydroxy-2-butanone (acetoin), 2,3-butanediol, phenol, and 2-methoxyphenol (guaiacol). This is believed to be the first report of the identification of volatile compounds associated with gray kernel.

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Walton, David A., Helen M. Wallace, and Richard Webb. "Ultrastructure and anatomy of Macadamia (Proteaceae) kernels." Australian Journal of Botany 60, no. 4 (2012): 291. http://dx.doi.org/10.1071/bt11148.

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Macadamia integrifolia Maiden & Betche and M. tetraphylla L.A.S.Johnson, and their hybrids, are cultivated for their edible kernels (mature embryos). Some kernels separate into halves (cotyledons) during post-harvest handling, and embryo cuticular characteristics may influence breakage. Some kernels have a gap between cotyledons before nut cracking, and this anatomical feature may be related to breakage. Kernels from cultivars producing high or low frequency of breakage were examined by transmission electron microscopy and scanning electron microscopy to identify differences in inner-cuticular wax. Whole seeds of each cultivar were opened without cracking to measure gaps between cotyledons and determine relationships between gaps and embryo breakage. Kernels from cultivars with low frequency of breakage had inner-epicuticular wax layers that were of the sculptured crust type whereas those of cultivars with high frequency of breakage were mainly of a wax-film type. Gap width and length of kernels separate at nut opening were more than twice those for intact kernels. There was a negative relationship between whole-kernel percentage and gap width between cotyledons.

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De Silva, Anushika L., Wiebke Kämper, Helen M. Wallace, Steven M. Ogbourne, Shahla Hosseini Bai, Joel Nichols, and Stephen J. Trueman. "Boron Effects on Fruit Set, Yield, Quality and Paternity of Macadamia." Agronomy 12, no. 3 (March 11, 2022): 684. http://dx.doi.org/10.3390/agronomy12030684.

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Many tree crops experience sub-optimal yields and low fruit quality due to inadequate pollination, low fruit set, and poor crop nutrition. Boron (B) is a critical crop nutrient for fruit set because B levels affect pollen germination and pollen tube growth. However, the relationship between floral B concentration and fruit set is not well understood. The aim of this study was to determine the effect of B applications on the initial fruit set, yield, quality, and paternity of macadamia (Macadamia integrifolia). Cultivar ‘816’ trees received one of three treatments: (a) 0 g, (b) 15 g, or (c) 30 g B per tree prior to flowering. Boron application increased the B concentration of macadamia flowers. Application of 15 g B increased fruit set at 3 weeks after peak anthesis, but this higher initial fruit set was not translated into higher fruit set at 6 or 10 weeks after peak anthesis or higher yield. Boron application increased B concentrations in kernels but did not affect nut-in-shell (NIS) mass, kernel mass, kernel recovery, kernel oil concentration or incidence of whole kernels. Cultivar ‘816’ was highly outcrossing, with 97–98% cross-paternity among kernels from all treatments. Our results indicate that higher B concentration in macadamia flowers can be associated with an increased initial fruit set. However, high B levels did not affect yield, nut quality, or the proportion of self-pollinated fruit at maturity. The heavy dependence on outcrossing highlights the importance of inter-planting different cultivars and managing bee hives to sustain the productivity of macadamia orchards.

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Stephenson, R. A., E. C. Gallagher, V. J. Doogan, and D. G. Mayer. "Nitrogen and environmental factors influencing macadamia quality." Australian Journal of Experimental Agriculture 40, no. 8 (2000): 1145. http://dx.doi.org/10.1071/ea99077.

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Applications of nitrogen fertiliser in macadamia orchards remain high, despite indications that optimum yields and quality are obtained at a lower rate. This 6-year study examined the effect on quality of 230, 690 and 1150 g nitrogen/tree . year, applied in April (floral initiation), in April and June (inflorescence development), in April, June and November (rapid nut growth and premature nut drop), in April, June, November and January (nut maturation/oil accumulation) or monthly. Higher rates of nitrogen increased kernel recovery by 1% in 5 years out of 6. In 1 year only, 4 or more split applications of the medium and high rates of nitrogen increased kernel recovery by up to 1.6%. These increases were insufficient to compensate for depressed yields (17% lower) at high nitrogen. In good years, when yields were above average, kernel recovery tended to be high and in years with poor yields, kernel recovery tended to be low except when nuts were small. Moderate summer—early autumn rainfall of about 100 mm/month was associated with high kernel recovery whereas very heavy rainfall (>200 mm/month) during this period was detrimental. The percentage of first grade kernels was influenced most by season but was negatively correlated with the rate of nitrogen. Impurities, including immature, deformed, mouldy and insect-damaged kernels, were lowest at low rates of nitrogen and highest during wet harvest seasons. Time of nitrogen application had no significant effect on yield, kernel recovery, the percentage of first-grade kernels or impurities. For sustained high yield and quality, 355 g nitrogen, or 0.8 kg urea/tree.year, applied in April—June is indicated. Agronomic and economic advantages of reducing rates of nitrogen applied to macadamia orchards are enhanced by increasingly important environmental considerations. Multiple regression analyses indicated that the rate, strategy and timing of nitrogen application, rainfall, temperature, flushing and litterfall were correlated with kernel recovery and first-grade kernels but more work is needed to elucidate the significance of these factors.

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Le Lagadec, M. D. "Kernel brown centres in macadamia: a review." Crop and Pasture Science 60, no. 12 (2009): 1117. http://dx.doi.org/10.1071/cp08403.

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The incidence of kernel brown centres in macadamia (Macadamia integrifolia and M. tetraphylla and hybrids) has increased substantially in Australia. Although the defect amounts to only ~1% of all kernels processed in Australia, it costs the macadamia industry over AU$2 million per annum. Little formal research has been conducted, although the defect is mentioned widely in informal grower journals. Possible causal factors are reviewed in this article. Evidence suggests that kernel brown centres may be associated with exposure of enzymes in cell membranes and are also associated with incorrect nut-in-shell drying regimes. There appears to be an interaction among nut-in-shell moisture content, nut drying regime, and the incidence of brown centres. There is some indication that storage of wet nuts in poorly ventilated silos increases the potential for developing kernel brown centres. It is recommended that future research focusses on these issues.

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Trochoulias, T., and GG Johns. "Poor response of macadamia (Macadamia integrifolia Maiden and Betche) to irrigation in a high rainfall area of subtropical Australia." Australian Journal of Experimental Agriculture 32, no. 4 (1992): 507. http://dx.doi.org/10.1071/ea9920507.

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Bearing macadamia trees (cv. Keauhou 246), received varying rates of irrigation at weekly intervals over 8 years, and the effects on nut yield and tree size were measured. Annual rainfall ranged between 1232 and 2283 mm and was supplemented by 9-24 irrigations per year. Unsatisfied evaporative demand in the control treatment was estimated to vary from 1 to 380 mm per season. Canopy and trunk areas were not affected by irrigation. The average annual yield per unit of canopy area across all treatments was about 900 g/m2 of nut in shell. Irrigation reduced nut in shell yield per unit trunk area slightly, and depressed the individual mean weight of nut in shell by an average of 5%. There was a highly significant (P<0.01) inverse linear relationship between individual nut weight and irrigation amount, with an individual mean nut in shell reduction of 7% at the highest irrigation rate. Kernel weight, as a percentage of total nut in shell weight (kernel recovery), was not affected by irrigation, but the percentage of kernels that floated in tap water (grade 1 kernels) was 2.8% higher from control trees than from irrigated trees.

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O’Hare, Tim J., Hung Hong Trieu, Bruce Topp, Dougal Russell, Sharon Pun, Caterina Torrisi, and Dianna Liu. "Assessing Fatty Acid Profiles of Macadamia Nuts." HortScience 54, no. 4 (April 2019): 633–37. http://dx.doi.org/10.21273/hortsci13418-18.

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The kernel of the macadamia nut (Macadamia integrifolia and M. tetraphylla) is very high in oil, accounting for about three -quarters of their mass. In the current investigation, oil extracts from 20 breeding accessions and 14 cultivars had a range of 12.3% to 17.0% saturated fat, averaging 14.2%. Although all samples were found to be very high in “healthy” monounsaturated fats, the level of saturated fat slightly exceeds that of many other nuts that are able to make qualified health claims. The lowest saturated fat content (12.3%) corresponded to 4.6 g saturated fat/50 g kernels, which was slightly greater than the 4.0 g maximum. Despite this, potential exists to develop a reduced-saturated fat macadamia by combining characteristics found in different lines. The current trial indicates that lower total saturated fat was associated with a stronger ability to partition C16 and C18 fats to their monounsaturated fatty acids, or to elongate C16:0 to C18:0 and subsequently desaturate C18:0 to C18:1. It was also observed that the pollinizer parent is likely to have an influence on saturated fat content, although this would need to be confirmed in controlled pollination trials. Macadamia varieties generally outcross, and because the edible kernel (embryo) is formed from a pollinated ovule, it is likely any future reduced-saturated fat line would also require a reduced-saturated fat pollinizer parent.

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Guthrie, John, Colin Greensill, Ray Bowden, and Kerry Walsh. "Assessment of quality defects in macadamia kernels using NIR spectroscopy." Australian Journal of Agricultural Research 55, no. 4 (2004): 471. http://dx.doi.org/10.1071/ar03179.

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Spectral data were collected of intact and ground kernels using 3 instruments (using Si-PbS, Si, and InGaAs detectors), operating over different areas of the spectrum (between 400 and 2500 nm) and employing transmittance, interactance, and reflectance sample presentation strategies. Kernels were assessed on the basis of oil and water content, and with respect to the defect categories of insect damage, rancidity, discoloration, mould growth, germination, and decomposition. Predictive model performance statistics for oil content models were acceptable on all instruments (R2 > 0.98; RMSECV < 2.5%, which is similar to reference analysis error), although that for the instrument employing reflectance optics was inferior to models developed for the instruments employing transmission optics. The spectral positions for calibration coefficients were consistent with absorbance due to the third overtones of CH2 stretching. Calibration models for moisture content in ground samples were acceptable on all instruments (R2 > 0.97; RMSECV < 0.2%), whereas calibration models for intact kernels were relatively poor. Calibration coefficients were more highly weighted around 1360, 740 and 840 nm, consistent with absorbance due to overtones of O-H stretching and combination. Intact kernels with brown centres or rancidity could be discriminated from each other and from sound kernels using principal component analysis. Part kernels affected by insect damage, discoloration, mould growth, germination, and decomposition could be discriminated from sound kernels. However, discrimination among these defect categories was not distinct and could not be validated on an independent set.It is concluded that there is good potential for a low cost Si photodiode array instrument to be employed to identify some quality defects of intact macadamia kernels and to quantify oil and moisture content of kernels in the process laboratory and for oil content in-line. Further work is required to examine the robustness of predictive models across different populations, including growing districts, cultivars and times of harvest.

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Bai, S. H., S. J. Trueman, T. Gama, K. Jones, D. A. Walton, B. Randall, and H. M. Wallace. "Shelf life of macadamia kernels of different origin." Acta Horticulturae, no. 1256 (October 2019): 375–78. http://dx.doi.org/10.17660/actahortic.2019.1256.53.

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Shi, Rui, Haidong Bai, Biao Li, Can Liu, Zhiping Ying, Zhi Xiong, and Wenlin Wang. "Combined Transcriptome and Lipidomic Analyses of Lipid Biosynthesis in Macadamia ternifolia Nuts." Life 11, no. 12 (December 18, 2021): 1431. http://dx.doi.org/10.3390/life11121431.

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Macadamia nuts are considered a high-quality oil crop worldwide. To date, the lipid diversity and the genetic factors that mediate storage lipid biosynthesis in Macadamia ternifolia are poorly known. Here, we performed a comprehensive transcriptomic and lipidomic data analysis to understand the mechanism of lipid biosynthesis by using young, medium-aged, and mature fruit kernels. Our lipidomic analysis showed that the M. ternifolia kernel was a rich source of unsaturated fatty acids. Moreover, different species of triacylglycerols, diacylglycerol, ceramides, phosphatidylethanolamine, and phosphatidic acid had altered accumulations during the developmental stages. The transcriptome analysis revealed a large percentage of differently expressed genes during the different stages of macadamia growth. Most of the genes with significant differential expression performed functional activity of oxidoreductase and were enriched in the secondary metabolite pathway. The integration of lipidomic and transcriptomic data allowed for the identification of glycerol-3-phosphate acyltransferase, diacylglycerol kinase, phosphatidylinositols, nonspecific phospholipase C, pyruvate kinase 2, 3-ketoacyl-acyl carrier protein reductase, and linoleate 9S-lipoxygenase as putative candidate genes involved in lipid biosynthesis, storage, and oil quality. Our study found comprehensive datasets of lipidomic and transcriptomic changes in the developing kernel of M. ternifolia. In addition, the identification of candidate genes provides essential prerequisites to understand the molecular mechanism of lipid biosynthesis in the kernel of M. ternifolia.

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Albertson, P. L., J. K. Bursle, R. I. Forrester, and C. A. McConchie. "Hexose synthesis by cell wall invertase activity and its effects on the roasting behaviour of macadamia kernel." Australian Journal of Agricultural Research 57, no. 1 (2006): 47. http://dx.doi.org/10.1071/ar05144.

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After roast darkening (ARD) is a defect concealed in the raw macadamia kernel, only becoming evident upon roasting. Kernels susceptible to some forms of ARD reportedly have a higher glucose and fructose concentration. By developing a procedure to simulate ARD and through the inclusion of effector molecules we have demonstrated that the enzyme invertase is key to this form of ARD. Biochemical analysis of raw mature kernel has shown high invertase activity. Separating the extract into pellet and soluble fractions showed that the high invertase activity occurred in the pellet fraction containing the cell wall isoform and that the soluble fraction had little activity. A broad peak in crude cell wall invertase activity occurred between pH 3.75 and 5.0. Enzyme kinetics of the cell wall invertase from crude extracts assayed at pH 4 indicated a high level of activity (Vmax = 4.11 ± 0.55 mg glucose produced/g fresh weight tissue.h), a high affinity for sucrose (Km = 2.02 ± 0.96 mm), and inhibition by MgCl2 (K i = 71.2 ± 12.5 mm). We propose that the initial step in the processes leading to ARD in macadamia could involve membrane damage and subsequent modification of the kernel sugar composition by cell wall invertase.

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Galanti, Russell, Alyssa Cho, Amjad Ahmad, and Theodore Radovich. "Soil Amendments and Soil Profiling Impact on Macadamia Growth and Yield Performance." HortScience 54, no. 3 (March 2019): 519–27. http://dx.doi.org/10.21273/hortsci13572-18.

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Macadamia (Macadamia integrifolia, Maiden & Betche) orchard management in Hawaii can result in the loss of organic matter and soil degradation. The objective of this study was to determine the effects of macadamia husk mulch, husk mulch combined with biochar, husk mulch combined with effective microorganisms (EM), soil profiling, and wood chip mulch on yield, nut quality, root growth, and SPAD values during a 1-year study of mature macadamia orchards at two locations in Hawaii. A partial cost–benefit analysis was performed to compare the costs and yield benefits of each treatment. Soil profiling resulted in higher yields than any other treatment, at a mean of 86.6 kg wet-in-husk per tree. No treatments significantly affected nut quality or dry kernel weight. Nut quality was affected by harvesting time, with the earliest harvesting (Aug. 2017) period resulting in the highest recovery rate of number 1 grade kernels (33%). SPAD values increased with the husk mulch combined with EM (6.5%) treatment and soil profiling treatment (6.9%). Husk combined with EM caused an 87% increase in total root biomass during the study period due to increased proteoid root biomass. The soil profiling treatment had the second lowest estimated cost per hectare and had the highest estimated partial profit per hectare. Soil profiling is a destructive management practice and should be used judiciously until its long-term effects on orchard health are studied. The inoculation of EM or sugar signaling may have been responsible for the proliferation of proteoid roots with the husk mulch and EM treatment.

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Wright, M. G., P. A. Follett, and M. Golden. "Long-term patterns and feeding sites of southern green stink bug (Hemiptera: Pentatomidae) in Hawaii macadamia orchards, and sampling for management decisions." Bulletin of Entomological Research 97, no. 6 (November 12, 2007): 569–75. http://dx.doi.org/10.1017/s0007485307005305.

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AbstractSouthern green stink bug (Nezara viridula, Hemiptera: Pentatomidae) is a pest of macadamia nuts, causing pitting to kernels by feeding. In spite of its pest status, many aspects of the ecology of this insect in macadamia orchards are poorly understood. This study analyzes long-term N. viridula damage to macadamia nuts and investigates the extent to which damage to nuts occurs in the tree canopy, prior to nut-drop. We show that there are distinct seasonal peaks in damage detected after harvest and that, over six years of data collection, mean damage levels were fairly low, albeit with spikes in damage levels recorded. Sampling nuts at peak harvest periods from different strata in the trees and from the ground showed that incidence of damaged nuts within the canopy was typically half as high as on the fallen nuts. Damage to fallen nuts may have occurred prior to nut-drop, and continued to accumulate after nut-drop. These results show that management of N. viridula within macadamia canopies, as opposed to only on fallen nuts, is important. A sampling procedure and predictive model for estimating late-season damage based on early-season damage samples is provided. The model uses January and March damage measurements (based on samples with set level of accuracy), mean temperature and month of the year for which damage is predicted. Early-season damage of 6–10% predicts late-season damage levels that should justify N. viridula suppression based on the nominal threshold (13% damage) used by kernel processors to reject nuts based on damage.

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Tjiparuro, Z. "Challenges of designing a cracker for Morama bean – Short communication." Research in Agricultural Engineering 59, No. 1 (March 6, 2013): 35–37. http://dx.doi.org/10.17221/68/2011-rae.

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Experiments were done on Morama beans (Tylosema esculentum) using macadamia nut crackers. Results and subsequent design work done thereafter showed that the cracking of the beans, their alignment during cracking and separation of kernels from shells presented peculiar challenges unresolvable by conventional processes.    

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LITTLE, C. L., W. JEMMOTT, S. SURMAN-LEE, L. HUCKLESBY, and E. de PINNA. "Assessment of the Microbiological Safety of Edible Roasted Nut Kernels on Retail Sale in England, with a Focus on Salmonella." Journal of Food Protection 72, no. 4 (April 1, 2009): 853–55. http://dx.doi.org/10.4315/0362-028x-72.4.853.

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There is little published information on the prevalence of Salmonella in edible nut kernels. A study in early 2008 of edible roasted nut kernels on retail sale in England was undertaken to assess the microbiological safety of this product. A total of 727 nut kernel samples of different varieties were examined. Overall, Salmonella and Escherichia coli were detected from 0.2 and 0.4% of edible roasted nut kernels. Of the nut varieties examined, Salmonella Havana was detected from 1 (4.0%) sample of pistachio nuts, indicating a risk to health. The United Kingdom Food Standards Agency was immediately informed, and full investigations were undertaken. Further examination established the contamination to be associated with the pistachio kernels and not the partly opened shells. Salmonella was not detected in other varieties tested (almonds, Brazils, cashews, hazelnuts, macadamia, peanuts, pecans, pine nuts, and walnuts). E. coli was found at low levels (range of 3.6 to 4/g) in walnuts (1.4%), almonds (1.2%), and Brazils (0.5%). The presence of Salmonella is unacceptable in edible nut kernels. Prevention of microbial contamination in these products lies in the application of good agricultural, manufacturing, and storage practices together with a hazard analysis and critical control points system that encompass all stages of production, processing, and distribution.

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Stephenson, R. A., E. C. Gallagher, and B. J. Gogel. "Macadamia nut size and maturity influenced by lime and nitrogen applications." Australian Journal of Agricultural Research 53, no. 6 (2002): 677. http://dx.doi.org/10.1071/ar01146.

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A long-term study of the effects of lime and nitrogen on a young macadamia orchard included acidifying sulfate of ammonia treatments to separate pH and Ca effects of lime applications. Lime, per se, had no influence on yield, quality, or trunk girth growth. Annual nitrogen applications (with or without neutralising applications of lime), however, consistently depressed the size of nuts and kernels and the percentage of first grade kernels, but had no effect on yield or other quality characteristics. More nuts developed with N treatments but failed to fill effectively.

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Trueman, S. J., S. Richards, C. A. McConchie, and C. G. N. Turnbull. "Relationships between kernel oil content, fruit removal force and abscission in macadamia." Australian Journal of Experimental Agriculture 40, no. 6 (2000): 859. http://dx.doi.org/10.1071/ea00004.

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Delayed or extended fruit abscission in many cultivars of macadamia, Macadamia integrifolia (Proteaceae), necessitates multiple harvests from the orchard floor. However, it is not known whether there is a link between fruit maturation and timing of abscission. In this study, relationships between kernel oil content, nut size, removal force and abscission were investigated in 2 commercial orchards, one in Queensland (24˚S) and one in New South Wales (29˚S). Abscission lasted 6 months (March–September) at both sites due to differences in timing of abscission between cultivars and extended abscission within cultivars. Abscission was consistently associated with declines in fruit removal force, from more than 2 kgf in early March towards 1 kgf at the peak of abscission. Later abscission in cvv. A16 and 246, compared with cvv. 344 and 741, was correlated with more gradual declines in removal force. Fruits containing small nuts and kernels tended to possess lower removal forces and these fruits were often heavily represented in the population of fruits that abscised earliest. There was little or no difference in kernel oil content between fruits of different removal force or between sample dates for any cultivar, either for samples taken from the tree or from the orchard floor. Attainment of maximal oil content and onset of fruit abscission are therefore independent processes in macadamia. If abscission can be accelerated, it may be possible to advance the harvest of late-abscising cultivars such as A16 and 246 which retain mature nuts on the tree up to several months after maximal oil accumulation.

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Walton, David A., and Helen M. Wallace. "Delayed harvest reduces quality of raw and roasted macadamia kernels." Journal of the Science of Food and Agriculture 89, no. 2 (January 30, 2009): 221–26. http://dx.doi.org/10.1002/jsfa.3429.

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Wang, Yunyang, Li Zhang, Mengxiang Gao, Juming Tang, and Shaojin Wang. "Temperature- and Moisture-Dependent Dielectric Properties of Macadamia Nut Kernels." Food and Bioprocess Technology 6, no. 8 (June 1, 2012): 2165–76. http://dx.doi.org/10.1007/s11947-012-0898-2.

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Y. Sarig and H. Blas. "DEVELOPMENT OF A METHOD FOR SEPARATING MACADAMIA NUT KERNELS FROM CRACKED NUTS." Applied Engineering in Agriculture 16, no. 6 (2000): 665–70. http://dx.doi.org/10.13031/2013.5367.

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Palipane, Keerthi B., and Robert H. Driscoll. "The thin-layer drying characteristics of macadamia in-shell nuts and kernels." Journal of Food Engineering 23, no. 2 (January 1994): 129–44. http://dx.doi.org/10.1016/0260-8774(94)90082-5.

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Walton, David A., and Helen M. Wallace. "The effect of mechanical dehuskers on the quality of macadamia kernels when dehusking macadamia fruit at differing harvest moisture contents." Scientia Horticulturae 182 (January 2015): 119–23. http://dx.doi.org/10.1016/j.scienta.2014.10.053.

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Stephenson, RA, TS Rasmussen, and EC Gallagher. "Timing of nitrogen application to macadamias. 2. Storage carbohydrates." Australian Journal of Experimental Agriculture 29, no. 4 (1989): 575. http://dx.doi.org/10.1071/ea9890575.

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Samples of wood and bark were taken monthly from macadamia (Macadamia integrifolia Maiden and Betche) tree trunks and analysed for total 'fermentable' carbohydrates. Carbohydrates (%, w/w) were high during autumn-winter and declined to low levels in summer when oil was accumulating in kernels. Reproductive growth appeared to draw heavily on carbohydrate reserves. Vegetative growth, on the other hand, was not generally reflected in lower carbohydrate levels in tree trunks. Application of nitrogen (N) during summer resulted in higher carbohydrate levels than when applied in autumn or winter. Despite these differences, there was no apparent accumulation of carbohydrates in the months directly following application of N. The low N status of control trees was not reflected in low concentrations of storage carbohydrates. Wood tissues had a higher concentration of carbohydrates than bark, perhaps reflecting the sampling procedures used. Further work to quantify the contribution of storage carbohydrates and current photosynthesis to yield is justified.

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Fourie, P. C., and D. S. Basson. "Changes in the tocopherol content of almond, pecan and macadamia kernels during storage." Journal of the American Oil Chemists' Society 66, no. 8 (August 1989): 1113–15. http://dx.doi.org/10.1007/bf02670095.

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Walton, David A., Bruce W. Randall, Marie D. Le Lagadec, and Helen M. Wallace. "Maintaining high moisture content of macadamia nuts-in-shell during storage induces brown centres in raw kernels." Journal of the Science of Food and Agriculture 93, no. 12 (April 19, 2013): 2953–58. http://dx.doi.org/10.1002/jsfa.6123.

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Marcus, John P., Jodie L. Green, Ken C. Goulter, and John M. Manners. "A family of antimicrobial peptides is produced by processing of a 7S globulin protein in Macadamia integrifolia kernels." Plant Journal 19, no. 6 (September 1999): 699–710. http://dx.doi.org/10.1046/j.1365-313x.1999.00569.x.

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McFadyen, L. M., S. G. Morris, M. A. Oldham, D. O. Huett, N. M. Meyers, J. Wood, and C. A. McConchie. "The relationship between orchard crowding, light interception, and productivity in macadamia." Australian Journal of Agricultural Research 55, no. 10 (2004): 1029. http://dx.doi.org/10.1071/ar04069.

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Orchard crowding in the macadamia industry is common and there has been concern that it reduces yield and quality. To investigate this we monitored yield, nut quality, tree volume, and light interception in macadamia orchards (Macadamia integrifolia Maiden and Betche) that represented a range in crowding. The predicted rate of change in yield/ha with time remained positive, i.e. yield increased over time, for orchards with crowding levels up to a tree volume of 43 500 m3/ha and light interception of 94%. There was a trend for the rate of yield change to decrease with increasing tree volume/ha. For orchards with tree volume >43 500 m3/ha the rate was negative, indicating a slight decline in yield over time. There was no evidence of a detrimental effect of orchard crowding on percentage kernel recovery, unsound kernel, or grade 1 kernel. It appears that macadamia, unlike many other orchard crops, can maintain yield and quality up to a high level of orchard crowding. The implication of this is that timing of canopy management and optimum canopy dimensions will be dictated by management requirements for machinery access and effective spray coverage before yield decline becomes an issue.

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Loi, N. V., and P. T. Binh. "Variation of the chemical components of macadamia in Vietnam at different harvesting maturity." Food Research 6, no. 1 (February 20, 2022): 253–59. http://dx.doi.org/10.26656/fr.2017.6(1).090.

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Currently, macadamia is harvested mainly by collecting ripe fruits. This way of harvesting is expensive due to the reduced quality of the fruits falling to the ground. Thus, it is necessary to analyze the chemical components of macadamia at different maturity to identify the best time for mass harvest. In our study, lipid, protein, and carbohydrate contents in the kernel of macadamia in the 3 stages of growing (including 175, 195, and 215 days after fruiting) were determined by using analytical methods. These components increased gradually and reached the maximum values of 78.2±0.1%, 9.3±0.1%, and 7.8±0.2% for lipid, protein, and carbohydrate, respectively, 215 days after fruiting. Moreover, by using the HPLC method 13 amino acids, 14 amino acids, and 15 amino acids were identified at 175, 195, and 215 days after fruiting respectively. In all of these 3 stages, there were 7 non-substituting amino acids, including leucine, isoleucine, lysine, methionine, valine, phenylalanine, and histidine in the kernel of macadamia. The contents of phenylalanine, alanine, leucine, and glycine tended to increase in the developmental stages of macadamia. After 175 days, 195, and 215 days of harvest, 9 to 10 types of fatty acids were identified. Comparing two harvest times 195 and 215 days since fruiting, the fatty acid content of macadamia did not differ much. Therefore, the most appropriate time to harvest macadamia is from 195 to 215 days after fruiting.

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Meyers, N. M., D. O. Huett, S. C. Morris, L. M. McFadyen, and C. A. McConchie. "Investigation of sampling procedures to determine macadamia fruit quality in orchards." Australian Journal of Experimental Agriculture 39, no. 8 (1999): 1007. http://dx.doi.org/10.1071/ea99072.

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Summary. Macadamia kernel quality estimates are of fundamental importance to understanding tree responses to many experimental treatments and orchard management protocols. Experimental measures of macadamia kernel quality, collected under field conditions, traditionally rely on the average of 100 fruit, sampled from the estimated peak in fruit drop. To detect changes in kernel quality over a single season, we measured variation in fruit quality of macadamia cv. 344. To sample this variation we measured 10 fruit from 6 blocks of 3 trees at each of 7 sites, over 4 harvests made at monthly intervals. For all fruit collected we determined: husk, shell and kernel dry weights; kernel recovery (the percentage of kernel to kernel and shell weight); and kernel specific gravity from which oil content was estimated. A split-plot analysis of variance model was used to determine variance estimates for each of the fruit quality parameters measured. The percentages of partitioned total variance of the quality parameters were lowest for sites (3.6–6.7%), intermediate for harvests (3.3–41.1%) and highest for fruit (32.9–71.2%). Using these estimates, we investigated the influence of varying the number of replicates per site and fruits per replicate on kernel quality estimates. The analyses indicated that samples of 5 fruit, from each of 6 randomly located blocks within a site, represent the minimum replication required to detect commercially relevant changes in the kernel quality parameters measured. Larger sample sizes and increased replication did not significantly increase the precision of estimates.

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Trueman, S. J., C. A. McConchie, and C. G. N. Turnbull. "Ethephon promotion of crop abscission for unshaken and mechanically shaken macadamia." Australian Journal of Experimental Agriculture 42, no. 7 (2002): 1001. http://dx.doi.org/10.1071/ea01164.

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Promotion of fruit abscission in macadamia, Macadamia integrifolia (Proteaceae), has potential to reduce costs associated with prolonged harvesting of late-abscising cultivars. Effects of ethephon [(2-chloroethyl)phosphonic acid] on fruit removal force and crop abscission were monitored at 3 stages of the harvest season on both unshaken and mechanically shaken trees of the late-abscising macadamia cultivar A16. Ethephon application, tree shaking, or a combination of the 2 methods, accelerated crop removal from the tree at all stages during harvest. Early harvest before natural abscission resulted in little or no difference in nut-in-shell and kernel weight, kernel recovery and kernel oil content. Delaying ethephon application or tree shaking until commencement of natural abscission resulted in greater crop removal. Fruit removal force declined naturally towards 1 kgf at this stage, and was further reduced by ethephon application. The most effective approach for harvest acceleration was to reduce fruit removal force, before tree shaking, by spraying trees with ethephon.

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Walton, D., and H. Wallace. "DEHUSKER EFFECTS ON MACADAMIA KERNEL QUALITY." Acta Horticulturae, no. 687 (July 2005): 417–18. http://dx.doi.org/10.17660/actahortic.2005.687.64.

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McFadyen, L. M., S. G. Morris, C. A. McConchie, and M. A. Oldham. "Effect of hedging and tree removal on productivity of crowding macadamia orchards." Australian Journal of Experimental Agriculture 45, no. 6 (2005): 725. http://dx.doi.org/10.1071/ea04120.

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Hedging and 25% tree removal were investigated in a 6-year study as strategies to manage tree crowding in mature macadamia orchards. The trial orchard comprised 9-year-old macadamia (Macadamia integrifolia Maiden and Betche) trees, cultivar Kau (HAES 344), planted at 7 × 3.5 m and which had formed a hedgerow. In the hedged treatment, both sides of the hedgerow were lightly pruned annually with a mechanical hedger. In the tree removal treatment, 25% of trees were thinned out by removing every second tree in every second row. Hedging reduced yield in years 5 and 6 after the start of hedging, by 14 and 21%, respectively. Over 6 years, average yield reduction due to hedging was only 4%. Tree removal reduced yield/ha by 17% in the year immediately after thinning and this effect gradually reduced to 11% over the next 5 years as trees grew into the available space. Over 6 years, average yield reduction due to tree removal was 15%. The economic implications of the different patterns of yield reduction are discussed. Nuts dropped earlier in the tree removal treatment but there were no effects of hedging or tree removal on kernel recovery, unsound kernel or grade 1 kernel.

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34

Penter, M. G., I. Bertling, and A. D. Sippel. "Kernel breakage in the ‘Beaumont’ macadamia cultivar." Acta Horticulturae, no. 1109 (February 2016): 35–42. http://dx.doi.org/10.17660/actahortic.2016.1109.6.

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McConchie, C., A. Yang, R. Forrester, and B. Salter. "Development of predictors for macadamia kernel deterioration." Acta Horticulturae, no. 1120 (July 2016): 363–68. http://dx.doi.org/10.17660/actahortic.2016.1120.55.

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Hardner, Craig, João Costa e Silva, Emlyn Williams, Noel Meyers, and Cameron McConchie. "Breeding New Cultivars for the Australian Macadamia Industry." HortScience 54, no. 4 (April 2019): 621–28. http://dx.doi.org/10.21273/hortsci13286-18.

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In 2017, five new cultivars specifically selected for Australian conditions were released. These were developed from an improvement program initiated by Commonwealth Scientific and Industrial Research Organisation in the early 1990s. Progeny seeds were produced by crossing industry standard cultivars with other cultivars with elite kernel production per unit projected canopy area. Seedlings were planted at two densities (2 m and 4 m along rows) in field trials at Bundaberg in 1997 and 1998, and Northern New South Wales in late 1997, along with replicated plants of parents grafted onto seedling rootstocks. Trials were assessed for commencement of flowering, growth, yield, kernel recovery, and components of kernel quality over 8 years. Best linear unbiased predictions of clonal values were obtained for each individual progeny using a pedigree-based mixed linear model. A bio-economic model was used to estimate economic weights for a selection index of clonal values to identify elite candidates. Final approval of 20 candidates for second-stage assessment was made by an industry committee using selection index rankings and observations of tree field performance and kernel quality.

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Albertson, P. L., C. De Giovanni, R. H. Cocksedge, R. I. Forrester, A. L. Rae, R. Mason, and C. A. McConchie. "Inducing biochemical changes to simulate after-roast darkening in macadamia kernel." Australian Journal of Experimental Agriculture 45, no. 10 (2005): 1315. http://dx.doi.org/10.1071/ea04176.

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After-roast darkening is a defect in macadamia kernel evident only upon roasting that adversely affects kernel quality. After-roast darkening was artificially induced in 3 cultivars by incubating nut-in-shell of high moisture content (about 22% w/w) at elevated temperatures in either sealed or unsealed polyethylene bags before drying to 1.5% kernel moisture. After oil roasting, darkening was more evident in kernel from nut-in-shell incubated for 24 h in sealed bags at temperatures greater than or equal to 47.5°C. At an incubation temperature of 50°C the critical incubation period was 12 h for nut-in-shell treated in sealed bags. In raw kernel induced to exhibit high after-roast darkening upon roasting, the concentrations of the hexoses, glucose and fructose were elevated and levels of sucrose were reduced compared to non-induced kernel. The change in kernel sugar composition increased with increasing incubation temperature. A loss in cellular viability was also associated with kernel susceptibility to after-roast darkening. These results indicate that after-roast darkening might result from reactions, possibly enzymatic, that change the kernel sugar composition as a result of a loss in membrane integrity.

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38

Ito, Philip J. "RELATIONSHIP OF HAWAIIAN MACADAMIA CULTIVARS AND KERNEL QUALITY." Acta Horticulturae, no. 370 (September 1995): 33–38. http://dx.doi.org/10.17660/actahortic.1995.370.5.

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39

KOAZE, Hiroshi, Paul N. KARANJA, Michiyuki KOJIMA, Naomichi BABA, and Ken-ichi ISHIBASHI. "Lipid Accumulation of Macadamia Nuts during Kernel Development." food preservation science 28, no. 2 (2002): 67–73. http://dx.doi.org/10.5891/jafps.28.67.

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40

Bittenbender, H. C., N. V. Hue, Kent Fleming, and Hilary Brown. "Sustainability of Organic Fertilization of Macadamia with Macadamia Husk–Manure Compost." HortScience 31, no. 4 (August 1996): 670c—670. http://dx.doi.org/10.21273/hortsci.31.4.670c.

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A fertilization experiment, started in 1989, evaluated the merits of macadamia husk-manure compost as fertilizer for the production of macadamia. Three fertilization treatments were compared at four sites over 4 years on the MacFarms of Hawaii Honomalino orchard. The treatments were conventional fertilization, a combination of solid and liquid mineral fertilizers annually adjusted by the orchard manager based on leaf and soil analysis; compost only as 5 tons of a macadamia husk-cattle manure compost applied annually between July and October; and compost plus supplemental mineral fertilizers deemed needed by the orchard manager based on leaf and soil analysis. In-shell nut and kernel yield and quality was not significantly different between treatments. Change in leaf nutrient values appears minimum except for slightly lower N at two sites for the compost treatment. Higher Mg was noted for the compost but not the compost plus treatments at the irrigated sites. The effect of compost on the soil nutrient levels was more distinct and may have a delayed and longer term effect. Total exchange capacity of the soil increased, as did soil pH, Ca, Mg, K, and Na. Organic matter increased only at the site with least soil. Extractable soil Fe decreased, this maybe related to the change in pH, but had no consistent effect on leaf Fe. Compost fertilization was not considered sustainable as the cost of compost and its application exceeded conventional fertilization.

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41

Wasilwa, Lusike A., Grace W. Watani, N. Ondabu, A. Nyaga, B. Kagiri, and S. Kiiru. "481 Performance of Macadamia Varieties in Three Agroecological Zones." HortScience 35, no. 3 (June 2000): 477B—477. http://dx.doi.org/10.21273/hortsci.35.3.477b.

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Although macadamia was introduced to Kenya in 1946, it was not until the 1960s that commercial cutlivation commenced in the central, eastern, and western highlands. In the 1970s, 300 macadamia trees in the Central and Eastern highlands were selected based on nut yield and tree characteristics. In 1981, a subset of 25 of the most outstanding macadamia clones were planted (1979–1987) and evaluated at the National Horticulture Research Centre in Thika. Trial orchards, consisting seven to 15 clones (EMB-1, EMB-2, EMB-H, KMB-1, KMB-3, KMB-4, KRG-1, KRG-3, KRG-4, KRG-15, MRG-1, MRG-20, MRG-24, MRU-25, and TTW-2), were established in 1982, 1986, and 1989. The trials were set up as RCBD with five blocks and three to eight plants of each clone per block. Results from trial orchards show that macadamia hybrids (a natural hybrid between M. integrifolia and M. tetraphylla) EMB-H, KMB-3, and KMB-4 perform well at the higher elevations (>1700 m). The most outstanding clones of M. integrifolia with wide adaptability (1400 to 1750 m) were EMB-1, KRG-15, and MRG-20. Three distinct nut-bearing patterns [single peak (most varieties), bimodal peak, and ever-bearing] were observed. Nut clusters contain an average of 10 nuts (M. integrifolia) or 25 nuts (macadamia hybrid). Ten-year-old trees yield between 30 to 60 kg of nuts a year with kernel recovery of 28% to 41%.

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Kaneshiro, Wendy S., Catherine G. Cavaletto, C. S. Tang, and Anne M. Alvarez. "Gray Kernel Disease of Macadamia Nut: Are Bacteria Involved?" Plant Health Progress 4, no. 1 (January 2003): 32. http://dx.doi.org/10.1094/php-2003-0825-01-hn.

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These data point to but do not prove a bacterial etiology for gray kernel disease, and implicate Enterobacter cloacae as one of the causal agents. Other bacteria also may be involved. Accepted for publication 11 July 2003. Published 25 August 2003.

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43

Liang, Tung, Suhas K. Mehra, and M. A. Khan. "A macadamia nut curing system for improving kernel recovery." Journal of Agricultural Engineering Research 43 (May 1989): 103–11. http://dx.doi.org/10.1016/s0021-8634(89)80010-1.

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44

Walton, David A., and Helen M. Wallace. "Dropping macadamia nuts-in-shell reduces kernel roasting quality." Journal of the Science of Food and Agriculture 90, no. 13 (July 14, 2010): 2163–67. http://dx.doi.org/10.1002/jsfa.4063.

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45

Liang, Tung, Jason Chou, and Ronald Knapp. "Notching and freezing effect on macadamia nut kernel recovery." Journal of Agricultural Engineering Research 41, no. 1 (September 1988): 43–52. http://dx.doi.org/10.1016/0021-8634(88)90202-8.

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O’Connor, Katie, Ben Hayes, Craig Hardner, Mobashwer Alam, and Bruce Topp. "Selecting for Nut Characteristics in Macadamia Using a Genome-wide Association Study." HortScience 54, no. 4 (April 2019): 629–32. http://dx.doi.org/10.21273/hortsci13297-18.

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Current macadamia breeding programs involve a lengthy and laborious two-stage selection process: evaluation of a large number of unreplicated seedling progeny, followed by replicated trials of clonally propagated elite seedlings. Yield component traits, such as nut-in-shell weight (NW), kernel weight (KW), and kernel recovery (KR) are commercially important, are more easily measured than yield, and have a higher heritability. A genome-wide association study (GWAS) combined with marker-assisted selection offers an opportunity to reduce the time of candidate evaluation. In this study, a total of 281 progeny from 32 families, and 18 of their 29 parents have been genotyped for 7126 single nucleotide polymorphism (SNP) markers. A GWAS was performed using ASReml with 4352 SNPs. We found five SNPs significantly associated with NW, nine with KW, and one with KR. Further, three of the top 10 markers for NW and KW were shared between the two traits. Future macadamia breeding could involve prescreening of individuals for desired traits using these significantly associated markers, with only predicted elite individuals continuing to the second stage of selection, thus potentially reducing the selection process by 7 years.

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Srichamnong, W., M. Wootton, and G. Srzednicki. "LIPOXYGENASE AND PEROXIDASE ACTIVITY OF MACADAMIA KERNEL AFTER THERMAL PROCESSING." Acta Horticulturae, no. 943 (February 2012): 81–86. http://dx.doi.org/10.17660/actahortic.2012.943.7.

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48

Herbert, Steven W., David A. Walton, and Helen M. Wallace. "Pollen-parent affects fruit, nut and kernel development of Macadamia." Scientia Horticulturae 244 (January 2019): 406–12. http://dx.doi.org/10.1016/j.scienta.2018.09.027.

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Walton, David A., and Helen M. Wallace. "Quality changes in macadamia kernel between harvest and farm-gate." Journal of the Science of Food and Agriculture 91, no. 3 (October 27, 2010): 480–84. http://dx.doi.org/10.1002/jsfa.4209.

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50

Mai, Thuy T. P., Craig M. Hardner, Mobashwer M. Alam, Robert J. Henry, and Bruce L. Topp. "Phenotypic Characterisation for Growth and Nut Characteristics Revealed the Extent of Genetic Diversity in Wild Macadamia Germplasm." Agriculture 11, no. 7 (July 19, 2021): 680. http://dx.doi.org/10.3390/agriculture11070680.

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Macadamia is a recently domesticated Australian native nut crop, and a large proportion of its wild germplasm is unexploited. Aiming to explore the existing diversity, 247 wild accessions from four species and inter-specific hybrids were phenotyped. A wide range of variation was found in growth and nut traits. Broad-sense heritability of traits were moderate (0.43–0.64), which suggested that both genetic and environmental factors are equally important for the variability of the traits. Correlations among the growth traits were significantly positive (0.49–0.76). There were significant positive correlations among the nut traits except for kernel recovery. The association between kernel recovery and shell thickness was highly significant and negative. Principal component analysis of the traits separated representative species groups. Accessions from Macadamia integrifolia Maiden and Betche, M. tetraphylla L.A.S. Johnson, and admixtures were clustered into one group and those of M. ternifolia F. Muell were separated into another group. In both M. integrifolia and M. tetraphylla groups, variation within site was greater than across sites, which suggested that the conservation strategies should concentrate on increased sampling within sites to capture wide genetic diversity. This study provides a background on the utilisation of wild germplasm as a genetic resource to be used in breeding programs and the direction for gene pool conservation.

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Journal articles on the topic 'Macadamia kernels'

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