Air speed and plastic crate vent-holes for wine grape quality during postharvest dehydration: commercial and laboratory studies

Influence of the drying process of Cascade hop and the dry-hopping technique on the chemical, aromatic and sensory quality of the beer

Drying techniques are important for hop storage and quality. The stage of hop addition in beer is another important issue. This study focuses the impact of two drying techniques [freeze-dryer (F) and hot-stove (H)] of Cascade hop, on the chemical, aromatic and sensory quality of beer, comparing beers produced without (BF and BH) and with dry-hopping technique (BFDH and BHDH). Dry-hopping with H significantly increased the bitterness index and reduced the titratable acidity. Isoamyl acetate (450.60 μg/L) and ethyl caprylate (313.60 μg/L) were in high content especially in BH while, ethyl-n-caproate (359.37 μg/L) had the highest content in BF. The beers made with dry-hopping technique, had a significantly higher content in terpenes especially in BFDH (1006.18 μg/L). Sensory evaluation indicated difference preferences, with freeze-dried hop beers generally favored. In conclusion, depending on the type of beer desired, hops dried in different way and a specific hopping technique can be chosen.

Postharvest wine grape dehydration: ethanol dissipation from grape and biochemical changes

BACKGROUND

During postharvest dehydration, grapes are subject to metabolic changes including ethanol anabolism and catabolism. These changes affect the quality of the final product and ethanol production is a key step. Ethanol dissipation has never been measured during postharvest wine grape dehydration. Thus, the present study aimed to: (i) monitor ethanol dissipation and (ii) investigate chemical-biochemical changes in berries during dehydration.

RESULTS

Ethanol dissipation from Raboso grapes, under controlled postharvest dehydration, was found to comprise up to 36% of weight loss (w.l.). Moreover, the activity of enzymes involved in the anaerobic metabolism of grapes was investigated. Ethanol dissipation was highly correlated with grape weight loss (r2  = 0.989). Alcohol dehydrogenase activity, responsible for the reduction of ethanol to acetaldehyde, declined significantly with w.l. Similarly, pyruvate decarboxylase and lactate dehydrogenase reduced their activity. High lipoxygenase activity was measured at 27% w.l., whereas polyphenol oxidation was constant and declined in the last sampling.

CONCLUSION

Ethanol dissipation during postharvest dehydration allows for reducing anaerobic metabolism and promotes oxidative metabolism. The sensor used can be a useful commercial tool for monitoring berry metabolism. © 2023 Society of Chemical Industry.

High-performance bioelectronic tongue for the simultaneous analysis of phenols, sugars and organic acids in wines

BACKGROUND

Electronic tongues have been widely used to analyze wines. However, owing to the complexity of the matrix, the problem is not completely solved and further improvements are required.

RESULTS

A high-performance potentiometric bioelectronic tongue (bio-ET) specifically devoted to the assessment of wine components is presented. The novelty of this system is due to two innovative approaches. First, the improved performance is obtained through the use of potentiometric biosensors based on carboxylated polyvinyl chloride (PVC) membranes, where enzymes (glucose oxidase, tyrosinase, laccase, and lyase) specific to compounds of interest are linked covalently. Second, the performance is further enhanced by introducing electron mediators (gold nanoparticles or copper phthalocyanine) into the PVC membrane to facilitate the electron transfer process. Individual sensors exposed to target analytes (glucose, catechol, cysteine, or tartaric acid) show a linear behavior, with limits of detection in the region of 10-4  mol L-1 for all the compounds analyzed, with excellent reproducibility (coefficient of variation lower than 3%). Sensors combined to form a bio-ET show excellent capabilities. Principal component (PC) analysis can discriminate monovarietal white wines (PC1 77%; PC2 15%) and red wines (PC1 63%; PC2 30%). Using partial least squares, the bio-ET can provide information about chemical parameters, including glucose, total polyphenols, total anthocyanins, free and total sulfur dioxide, total acidity, and pH with R2 between 0.91 and 0.98 in calibration and between 0.89 and 0.98 in validation.

CONCLUSIONS

This advanced instrument is able to assess the levels of seven parameters in a single measurement, providing an advantageous method to the wine industry. © 2023 Society of Chemical Industry.

Novelty of Italian Grape Ale (IGA) beer: Influence of the addition of Gamay macerated grape must or dehydrated Aleatico grape pomace on the aromatic profile

A new category of fruit style beer resulting from the addition of grape matrices is named Italian Grape Ale (IGA). In this paper, we report data on an experimental work to produce IGA beers, adding macerated (CO2 or N2) red Gamay grape must or Aleatico grape pomace resulting from a grape dehydration process. Our hypothesis, that these wine processes can produce volatile organic compounds (VOCs) to characterize these IGA beers which was confirmed by chemical, sensory and aromatic results. IGA beers especially the one with gas-macerated grape musts (IGA-C and IGA-N) showed higher alcohol content than ALE beer (Control) and a higher polyphenol content and antioxidant activity. As regards VOCS, IGA beers increased the concentration of some classes (i.e., alcohols, esters, norisoprenoids) and IGA-N was better characterized by specific compounds such as isobutyric acid, phenylacetate, tyrosol, ethyl hydrogen succinate. Finally, E-nose and sensory evaluation discriminated significantly all the IGA beers.