Производство алкогольных напитков

Sourdough starter was initially prepared as described by Catzeddu (2019) and continuously backslopped at room temperature by adding fresh dark rye flour and the flour mixture to previously fermented sourdough at a ratio of 3:7 (w/w), to identify competitive strains in starters (Jin et al., 2020). Three yeasts (isolated S. cerevisiae 22A, isolated P. kudriavzevii 44A from above spontaneous sourdough, and commercial S. cerevisiae CR51) were respectively cultivated for 2 days at 28 °C on yeast extract peptone dextrose (YMPD) broth consisting of 0.3% (w/v) yeast extract, 0.3% (w/v) malt extract, 0.5% (w/v) peptone, and 1% (w/v) glucose. For the lactic acid bacterium, isolated L. plantarum 15 from spontaneous sourdough in Pyeongchang, South Korea, was cultivated for 2 days at 37 °C on MRS broth in addition to 1% (w/v) maltose and 1.5% (w/v) yeast extract. After inoculation with approximately 2% (v/v) of respective yeast cultures pre-grown statically in sterile unchaptalized apple juice for 48 h at 28 °C, 300 mL of sterile chaptalized apple juice was, respectively, fermented without agitation for 14 days at 28 °C in a sterile 400 mL brown fermenter with a screw-cap. In addition, approximately 2% (v/v) of L. plantarum pre-grown statically in sterile unchaptalized apple juice was simultaneously inoculated and incubated for 36 h at 35 °C.

Rhizopus was inoculated onto YPD medium and cultured at 30 °C until the spores matured. Then, Rhizopus moss was washed with 0.05% Tween-80 and shaken for 2 min in a vortex. The spore suspension was filtered and diluted to 107 spores/mL. S. fibuligera YRNN and S. cerevisiae were inoculated into YPD broth and cultured at 30 °C for 48 h and then diluted to 107 cfu/mL. Rice powder solid starters of the three strains were made with sterilized rice powder. Three rice powders were sprayed with a 2% (w/v) suspension of three microorganisms separately and cultured at 30 °C for 3 days and dried to obtain dry Rhizopus, S. fibuligera YRNN and S. cerevisiae starters for subsequent winemaking.

Thirty grams of rice was filled into a 250 mL Erlenmeyer flask, and 42 mL of deionized water was added. The starters of Rhizopus Q303, YRNN and S. cerevisiae were inoculated into sterilized rice. The amounts of the three starters are shown below in Table S1. The difference between S-1 and S-6 is that S-6 was under airtight conditions and sealed with a plastic film. All samples were incubated at 30 °C for 3 days in duplicate and then stored at − 20 °C for later study.

For this chromatographic method, outlier detection was performed using the Jackknife test. Four outliers were detected and removed in the solvent curve, and three outliers were removed from the matrix-matched curve. This is in accordance with the recommended limit for removing outliers (22.2% of the original data) (Souza and Junqueira 2005). After this removal, the residuals from both curves were normally distributed (p > 0.10), independent (p < 0.05), and homoscedastic (p < 0.05), according to the specific parameters estimated for Ryan–Joiner, Durbin–Watson, and Brown–Forsythe tests, respectively (Table 2). The regression (evaluated by ANOVA) was also significant (p < 0.001), and the lack of fit was not significant (p > 0.05) for both curves, confirming the linearity of the solvent and the matrix-matched curves. When the slope from solvent curve is compared to the matrix-matched curve, significant difference can be observed (p < 0.05). Since matrix effect was verified, further validation steps were performed using matrix-matched curves.

Green jujubes (Zizyphus jujuba cv. Muzao) were collected from in Lvliang city of Shanxi province, China in September 2018. Intact fruits of similar shape and size were collected without any physical injuries. The samples were transported to the lab and frozen at − 20 °C. Brewing highly active dry yeast was purchased from Angel Yeast Co., Ltd (Hubei, China). L-ascorbic acid (purity ≥ 99.7%), 3,5-Dioitrosalicylic acid, potassium ferricyanide and potassium persulfate were obtained from Tianjin Guangfu Technology Development Co., Ltd (Tianjin, China). Gallic acid (GA), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were provided from Shanghai Yuanye Bio-Technology Co., Ltd (Shanghai, China). 2,6-Dichloroindophenol sodium salt (purity ≥ 95%) was obtained from Shanghai Ica Biotechnology Co., Ltd. (Shanghai, China). The Folin-Ciocalteu reagent was provided from Hefei Bomei Biotech Co., Ltd. (Anhui, China). Other reagents used were of analytical grade.

The batch fermentation was carried out in 500 mL sterile conical flasks and each flask contained 100 mL of juice obtained from different mango varieties. 2.5 mL of Saccharomyces cerevisiae MTCC 178 (S1) and ISY (S2) inoculum added in the must samples and incubated at 25 °C for 15 days. After 15 days, the fermented juices filtered through muslin clothes with manual pressing. The extracted juice then clarified by bentonite (a clarifying agent). The clarifying agent prepared by dissolving 500 g of bentonite in 2 l of boiling water and stirred properly to a gel form. This was then allowed to stand for 24 h. Then, 150 g of the gel-like bentonite was added into each of the wine samples followed by stirring to get it dissolved properly. After 15 days of clarification, filtration was done using muslin cloth, sieve and syphon tubes sterilized with 70% (v/v) alcohol. All the wine samples were syphoned into the sieve containing four layers of muslin cloth. The residues removed and the filtrates collected for further physiochemical analysis.