Littérature scientifique sur le sujet « Post-harvest withering »

Withering is a practice traditionally used in various regions to produce sweet or dry wines. During withering there is an increase in sugar content but also a modification in volatile compound profiles. Controlling metabolic changes through the dehydration process to obtain wines with desired characteristics is therefore a challenging opportunity. The effects of two different withering technologies, post-harvest or on-vine with blocked sap vessel flow, on the volatile profile of young and aged Corvina red wines was investigated. The results showed that modulation of wine aroma due to the withering process is associated with fermentative metabolites, such as esters, higher alcohols, and acids, as well as grape-related compounds such as C6 alcohols, terpenes and norisoprenoids. Significant differences were also found by comparing the two withering techniques. Post-harvest in a traditional “fruttaio” warehouse wines showed higher content of ethyl acetate, ethyl butanoate, β-citronellol and 3-oxo-α-ionol, whereas post-harvest withering on-vine increased β-damascenone in wines. The type of withering technique has an influence on the evolution of some aroma compounds during the aging of wine, among them linalool, (E)-1-(2,3,6-trimethylphenyl)buta-1,3-diene (TPB), n-hexyl acetate, ethyl acetate, ethyl 3-methylbutanoate, 3-oxo-α-ionol and β-damascenone.

Tea is one of three major non-alcoholic beverages that are popular all around the world. The economic value of tea product largely depends on the post-harvest physiology of tea leaves. The utilization of quantitative reverse transcription polymerase chain reaction is a widely accepted and precise approach to determine the target gene expression of tea plants, and the reliability of results hinges on the selection of suitable reference genes. A few reliable reference genes have been documented using various treatments and different tissues of tea plants, but none has been done on post-harvest leaves during the tea manufacturing process. The present study selected and analyzed 15 candidate reference genes: Cs18SrRNA, CsGADPH, CsACT, CsEF-1α, CsUbi, CsTUA, Cs26SrRNA, CsRuBP, CsCYP, CselF-4α, CsMON1, CsPCS1, CsSAND, CsPPA2, CsTBP. This study made an assessment on the expression stability under two kinds of post-harvest treatment, turn over and withering, using three algorithms—GeNorm, Normfinder, and Bestkeeper. The results indicated that the three commonly used reference genes, CsTUA, Cs18SrRNA, CsRuBP, together with Cs26SrRNA, were the most unstable genes in both the turn over and withering treatments. CsACT, CsEF-1α, CsPPA2, and CsTBP were the top four reference genes in the turn over treatment, while CsTBP, CsPCS1, CsPPA2, CselF-4α, and CsACT were the five best reference genes in the withering group. The expression level of lipoxygenase genes, which were involved in a number of diverse aspects of plant physiology, including wounding, was evaluated to validate the findings. To conclude, we found a basis for the selection of reference genes for accurate transcription normalization in post-harvest leaves of tea plants.

The grape berry withering process is often seen as a means to concentrate the constituents of the berry via water removal, however, recent molecular studies have indicated that the reprogramming of biosynthetic pathways that impart the unique aroma and flavour of the final wine also occur. Metabolic analysis was performed using GC-MS and LC-MS on Corvina berry dehydrated for up to 108 days. The temporal pattern of metabolic changes and time-series relationship between various classes of metabolites were investigated on berries sampled at 23-time points. Principal component analysis of both GC-MS and LC-MS datasets revealed three distinct phases of post-harvest withering; early (day 0–28), mid (day 35–66) and late (day 69–108) stages. Stress-associated amino acids such as proline, serine, ethanolamine, and leucine accumulated significantly during the mid and late stages of the drying process while phosphorylated glucose and fructose, sucrose, kestose and resveratrol increased massively across time. Unlike most of the identified metabolites, low molecular weight flavanols exhibited a consistent pattern of decline during the withering period. Our network analysis revealed that increased metabolic network connectivity occurred during the middle stage of withering, thus reflecting more coordinated metabolite changes while reduced network connectivity at early and late stages indicates minimal metabolite perturbation during these stages. The current prolonged berry withering experiment revealed the timing of metabolite interconversions in the central metabolism and provided critical clues that link the concentration effect, protein degradation, and the onset of stress-like conditions in drying berries.

In the Valpolicella area (Verona, Italy) Vitis vinifera cv. Corvina is the main grape variety used to produce Amarone wine. Before starting the winemaking process, the Corvina grapes are stored in a withering (i.e., dehydrating) warehouse until about 30% of the berry weight is lost (WL). This practice is performed to concentrate the metabolites in the berry and enrich the Amarone wine in aroma and antioxidant compounds. In compliance with the guidelines and strict Amarone protocol set by the Consorzio of Amarone Valpolicella, withering must be carried out by setting the grapes in a suitable environment, either under controlled relative air humidity (RH) conditions and wind speed (WS)—no temperature modification is to be applied—or, following the traditional methods, in non-controlled environmental conditions. In general, the two processes have different dehydration kinetics due to the different conditions in terms of temperature, RH, and WS, which affect the accumulation of sugars and organic acids and the biosynthesis of secondary metabolites such as stilbenes and glycoside aroma precursors. For this study, the two grape-withering processes were carried out under controlled (C) and non-controlled (NC) conditions, and the final compositions of the Corvina dried grapes were compared also to evaluate the effects on the organoleptic characteristics of Amarone wine. The findings highlighted differences between the two processes mainly in terms of the secondary metabolites of the dried grapes, which affect the organoleptic characteristics of Amarone wine. Indeed, by the sensory evaluation, wines produced by adopting the NC process were found more harmonious, elegant, and balanced. Finally, we can state how using a traditional system, grapes were characterised by higher levels of VOCs (volatile compounds), whilst wines had a higher and appreciable complexity and finesse.

Teh merupakan minuman herbal yang banyak dikonsumsi oleh masyarakat. Pengolahan daun bambu tabah (Gigantochloa nigrociliata BUSE-KURZ) menjadi teh merupakan upaya untuk memanfaatkan senyawa yang ada di dalamnya yang mampu memberikan karakter tersendiri untuk hasil produk teh nantinya. Penelitian ini dilakukan dengan tujuan untuk menentukan hasil dan karakteristik teh daun bambu tabah dari perlakuan waktu pelayuan dan suhu pengeringan yang berbeda. Penelitian ini telah dilaksanaka pada mulai bulan Mei 2019 sampai dengan bulan Juli 2019 di Laboratorium Pasca Panen Fakultas Teknologi Pertanian Universitas Udayana, Laboratorium Biokimia dan Nutrisi Fakultas Teknologi Pertanian Universitas Udayana dan Laboratorium Analisis Pangan Fakultas Teknologi Pertanian Universitas Udayana. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) yang terdiri dari dua faktor, faktor pertama yang digunakan dalam rancangan penelitian ini adalah waktu pelayuan dan faktor kedua yaitu suhu pengeringan. Faktor pertama terdiri dari tiga taraf yaitu (P1) : pelayuan 8 jam, (P2) : pelayuan 10 jam, dan (P3) : pelayuan 12 jam. Faktor kedua terdiri dari tiga taraf yaitu (T1): suhu 50 °C, (T2): suhu 60 °C, dan (T3): suhu 70 °C. Parameter yang diamati dalam penelitian terdiri dari analisis kimia meliputi kadar air, pH, total asam, total fenol, total flavonoid dan uji organoleptik terdiri dari warna air seduhan,aroma, dan rasa pada daun teh yang diseduh. Hasil penelitian menunjukan bahwa kandungan fenol tertinggi terdapat pada perlakuan waktu pelayuan 12 jam dengan suhu pengeringan 70 oC yaitu 114,5664 mg/100g. Untuk total flavonoid yang terbaik pada perlakuan waktu pelayuan 12 jam dengan suhu pengeringan 70 oC yaitu 27.1697 mg/100g. Tea is herbal drink that is consumed by many people. The processing of tabah bamboo leaves (Gigantochloa nigrociliata BUSE-KURZ) into tea is an effort to utilize the compounds in it that are able to give a distinctive character to the results of tea products later. This research was conducted with the aim of determining the yield and characteristics of tabah bamboo leaf tea from different treatment time withering and drying temperatures. This research has been carried out from May 2019 to July 2019 in the Post Harvest Laboratory of the Faculty of Agricultural Technology, Udayana University, Biochemical and Nutrition Laboratory, Faculty of Agricultural Technology, Udayana University and the Food Analysis Laboratory, Faculty of Agricultural Technology, Udayana University. This study uses a Completely Randomized Design (RAL) consisting of two factors, the first factor used in the design of this study is the duration of withering and the second factor is the drying temperature. The first factor consists of three levels, namely (P1): 8 hour withering, (P2): 10 hour withering, and (P3): 12 hour withering. The second factor consists of three levels, namely (T1): temperature 50 ° C, (T2): temperature 60 ° C, and (T3): temperature 70 ° C. The parameters observed in the study consisted of chemical analysis including water content, pH, total acid, total phenol, total flavonoids and organoleptic tests consisting of the color of the brewing water, aroma, and taste in the brewed tea leaves. The results showed that the best phenol content was found in the treatment of 12 hours withering time with a drying temperature of 70 oC, 114.5664 mg / 100g. For the best total flavonoids in the treatment time withering time of 12 hours with a drying temperature of 70 oC is 27.1697 mg / 100g.

I vini Passiti ottenuti da uve che hanno subito un processo di appassimento sono vini rinomati e apprezzati dai consumatori principalmente per le complesse note sensoriali dovute al particolare processo di vinificazione. La fase di sovra-maturazione è fortemente influenzata dai microrganismi presenti sull’acino e in particolare da Botrytis cinerea in forma nobile. La presenza di questa muffa favorisce la disidratazione dell’acino e modifica la composizione del mosto che, infatti, presenta un elevato tenore zuccherino e contiene metaboliti secondari prodotti dalla muffa che possono inibire il processo fermentativo. Date queste condizioni stressanti per i lieviti, la fermentazione spontanea è spesso accompagnata da elevata produzione di acidità volatile oltre che a blocchi o arresti fermentativi. Di conseguenza, per controllare meglio questa fase critica una strategia biotecnologica innovativa potrebbe essere l'utilizzo di colture starter di lieviti autoctoni ben adattati a queste condizioni. L’obiettivo di questo progetto di ricerca è stato - quindi - quello di acquisire conoscenze sulla diversità microbica associata alla produzione di alcuni vini italiani (quali Amarone, Vin Santo di Gambellara e Vino Santo Trentino) e di ottimizzare il processo di vinificazione attraverso l'uso di ceppi selezionati di B. cinerea e di lieviti autoctoni durante il processo di appassimento e la fermentazione. In questo contesto, è stata allestita un’ampia collezione di muffe, tra cui B. cinerea, isolate da uve appassite, e una collezione di lieviti costituita da lieviti Saccharomyces e non-Saccharomyces isolati durante il processo di affinamento in caratelli e durante la fase di fermentazione di mosto Garganega utilizzato per la produzione del Vin Santo di Gambellara. Per quento riguarda l’appassimento, a processo concluso, il vino ottenuto da queste uve è stato analizzato gas-cromatograficamente. I vini ottenuti hanno indicato differenze importanti tra le tesi inoculate e l'uva di controllo (non inoculata) per diversi composti volatili liberi. Come previsto, il livello più alto di 1-otten-3-olo (sapore di muffa) è stato trovato per i vini ottenuti da uve inoculato. Questi dati suggeriscono che l'inoculo di ceppi selezionati di B. cinerea su uva può influenzare le caratteristiche organolettiche del mosto/vino, consentendo così una diversificazione del prodotto finale. Per quanto riguarda le prove di fermentazione guidata, l'analisi dei vini ha rivelato che la fermentazione spontanea produce un elevato livello di acetato di etile rispetto alle tesi inoculate con i ceppi selezionati di S. cerevisiae. Pertanto, l'uso di ceppi autoctoni può limitare la produzione di acidità volatile. Inoltre, l'analisi dei composti volatile ha evidenziato come tutti i vini ottenuti dai mosti fermentati con i ceppi selezionati presentano aromi associati a frutta bianca, alla rosa mandorla, fragola e caramello enfatizzando le proprietà aromatiche e il sapore del Vin Santo di Gambellara. L'analisi sensoriale ha ulteriormente confermato le differenze tra i diversi vini suggerendo quindi che l'uso di ceppi selezionati può migliorare il processo di fermentazione di vini passiti. In conclusione, questo progetto di ricerca ha evidenziato che l'uso di ceppi indigeni opportunamente selezionati (muffe e lieviti) è in grado di migliorare l’intero processo di produzione dei vini passiti minimizzando i rischi di blocchi, arresti fermentativi e produzione di acidità volatile, nonchè di influenzare positivamente la qualità sensoriale del prodotto finito. Unitamente all’uso di culture starter, l'uso di metodi alternativi validi in sostituzione all’anidride solforosa (SO2) potrebbe migliorare l'impatto commerciale dei vini privi di conservanti chimici. In questo modo può essere soddisfatta la sempre più elevata domanda da parte dei consumatori di vini sicuri, salubri e organoletticamente distintivi.
The wines obtained from post-harvest dried grapes are renowned wines, appreciated by consumers because of their complex sensorial notes due to the special vinification process, which involves the withering of grapes. The over-ripening phase is strongly influenced by the heterogeneous fungal biota present on the grape berry skin, and particularly by Botrytis cinerea. The development of the noble rot in berries affects the composition of the grape juice that presents high sugar content and inhibitory substances, as well. Therefore, grape juice fermentation proceeds hardly and is often accompanied by high production of volatile acidity. To better control the critical steps of Passito winemaking process, i.e. withering and fermentation, the use of suitable selected starter cultures could be applied as an innovative biotechnological strategy. Aims of this project were to increase knowledge about the diversity and evolution of indigenous eukaryotic microbiota associated with the production of some selected Italian wines (i.e. Amarone, Vin Santo di Gambellara, and Vino Santo Trentino) and to optimize the whole winemaking process through the use of selected indigenous strains of B. cinerea and yeasts. To these purposes, a large collection of moulds including B. cinerea was assembled; while a collection of yeasts (Saccharomyces and non-Saccharomyces) from wine aging in barrels and from the fermentation process of Garganega grape juice used for the production of Vin Santo di Gambellara was constituted. The isolates were identified using phenotypic and molecular methods, and then the collections were dereplicated by RAPD-PCR, PCR-RFLP, TEs, and microsatellite analysis. These techniques allowed the detection of a high genetic biodiversity among the B. cinerea and yeast isolates. The presence of distinctive strains could differentiate the withering of the studied grapes and the fermentation process, consequently selected strains of B. cinerea and yeasts were further characterized for several oenological properties (i.e. laccase activity and fungicide resistance for B. cinerea; resistance to stressful conditions and production of secondary metabolites for yeasts). In this way, strains of B. cinerea, S. cerevisiae and Zygosaccharomyces spp. were selected and tested in pilot-scale induction and fermentation trials, respectively. Considering the withering phase, at the end of the process the grapes were crushed and the grape juices were fermented. The gas-chromatographic analysis of the obtained wines indicated important differences between the inoculated and control grapes for several free volatile compounds. As expected, higher level of 1-octen-3-ol (mould flavor) was found for the wines obtained from the inoculated grape. These data suggest that the inoculum of selected B. cinerea strains on grapes influence the organoleptic characteristics of the must/wine, thus allowing a diversification of the final product. As regard the fermentation phase, the use of indigenous S. cerevisiae and non-Saccharomyces strains improved the fermentation process of Vin Santo di Gambellara. Indeed, failure to initiate fermentation and stuck fermentation were avoided, and a lower level of ethyl acetate was produced respect to the spontaneous fermentation. All selected S. cerevisiae yeasts produced flavors associated with white fruit, rose note, almond note and strawberry and caramel fragrance that emphasized the aromatic and flavor properties of this Passito wine. In conclusion, this research project suggests that the use of selected indigenous strains (moulds and yeasts) could improve the fermentation process of Passito wines minimizing risky conditions and improving the sensory quality of the final product. In other side, the use of valid alternative methods to SO2 addiction could improve the commercial impact of the wines free of chemical preservatives. In this way the modern consumer demand for wines that are safe and characterized by particular organoleptic flavour can be satisfied.