Sensory properties of rehydrated Toona sinensis shoots after dehydrated by different drying methods and association with gamma-glutamyl transferase reaction.

Sulfur-containing compounds are responsible for the aroma of Toona sinensis shoot (TS). In this study, vacuum-freeze-drying (VFD), microwave-drying (MD), and hot-air-drying at 100 and 40 °C (HAD100 and HAD40, respectively), were applied to dehydrate perishable TS for preservation. VFD-TS retained most aroma of fresh/raw TS after rehydration. The content of sulfur-containing compounds reached to 118.00 µg/g with leading by methyl thiirane, (E,E)/(E,Z)/(Z,Z)-bis-(1-propenyl) disulfides, and (Z)/(E)-2-mercapto-3,4-dimethyl-2,3-dihydrothiophenes accounting for 86.33 %. They were undetected in the rehydrated MD-TS and HAD100-TS, as the indigenous enzymes in TS were deactivated under their dehydration conditions. Interestingly, the sulfur-containing compounds was restored by 77.47 % after the TS was treated by gamma-glutamyl transferase (GGT). Thus, the release of sulfur-containing compounds from TS could depend on GGT reaction. It was different from alliaceous vegetables relying on alliinase reaction. The results revealed the aroma formation in TS and provided an approach to enhance the aroma of TS dried by different methods.

Screening of Yeast in Various Vineyard Soil and Study on Its Flavor Compounds from Brewing Grape Wine.

In order to screen out Saccharomyces cerevisiae suitable for table grape fermentation, and compare it with commercial Saccharomyces cerevisiae in terms of fermentation performance and aroma producing substances, differences of fermentation flavor caused by different strains were discussed. In this experiment, yeast was isolated and purified from vineyard soil, 26s rDNA identification and fermentation substrate tolerance analysis were carried out, and the causes of flavor differences of wine were analyzed from three aspects: GC-MS, PCA and sensory evaluation. The results showed that strain S1 had the highest floral aroma fraction, corresponding to its high production of ethyl octanoate and other substances, and it had the characteristics of high sugar tolerance. The fruit sensory score of S3 wine was the highest among the six wines. Through exploration and analysis, it was found that compared with commercial Saccharomyces cerevisiae, the screened strains had more advantages in fermenting table grapes. The flavor of each wine was directly related to the growth characteristics and tolerance of its strains.

Effects of drying methods on the nutritional aspects, flavor, and processing properties of Chinese chestnuts.

To select a suitable drying process for using chestnut products in the food industry, this study investigated the effect of five drying methods, including natural drying, microwave drying (MD), hot air drying (HAD), freeze-vacuum drying (FVD) and microwave-vacuum drying (MVD) on the nutritional composition, flavor, and functional properties of dried chestnuts. The results indicated that the nutritional aspects and functional properties of chestnuts were enhanced by the freeze-drying process compared with the other four drying methods. The quality of the chestnuts dried using the MVD was second to the FVD. The hot-air dried products were quite similar to the naturally dried samples in terms of their functional component content and processability. In terms of the produce texture, the HAD was found to be the best. In total, 45 flavor components were identified in the samples, which comprised the following: 5 aldehydes, 4 alcohols, 4 esters, 8 terpenes, 16 hydrocarbons and, 8 others substances. The highest relative content of the ingredients in microwave-vacuum dried samples was pyrazine and 3-ethyl-2, 5-dimethyl. In the samples treated using the other four drying methods, benzyl alcohol was the ingredient with the highest concentration. Considering the fast drying rate, low energy consumption, and improved quality of chestnut products, MVD is the most suitable dehydration method for commercial production of Chinese chestnuts.

Fast isolation of highly active photosystem II core complexes from spinach.

Purification of photosystem II (PSII) core complexes is a time-consuming and low-efficiency process. In order to isolate pure and active PSII core complexes in large amounts, we have developed a fast method to isolate highly active monomeric and dimeric PSII core complexes from spinach leaves by using sucrose gradient ultracentrifugation. By using a vertical rotor the process was completed significantly faster compared with a swing-out rotor. In order to keep the core complexes in high activity, the whole isolation procedure was performed in the presence of glycine betain and pH at 6.3. The isolated pigment-protein complexes were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, absorption spectroscopy, 77 K fluorescence spectroscopy and high performance liquid chromatography. Our results show that this method is a better choice for quick and efficient isolation of functionally active PSII core complexes.