Studies On The Isolation,Identification And Characteristics Of Spoilage Microbes From Aging Yellow Rice Wine

Yellow rice wine is made from cereal(sticky rice in South China, husked millet and wheat in North China),fermented by lots of beneficial microbes from traditional rice wine starters(wheat koji/rice koji) through their saccharification and fermentation, and known as one of the world's three most ancient species of wine, together with French wine and German beer.However, the spoilage during aging is always a big problem in the wine industry. Furthermore, the mechanisms are not yet clearly, and few related reports were seen both domestic and overseas. Thus, this thesis isolated and identified the spoilage microbes that caused aging yellow rice wine corruption, studied the characteristics of spoilage microbes, and explored the sterilization effect of pulsed electric field (PEF) on the spoilage microbes, aiming to provide theoretical basis and practical guidance for solving the problem of spoilage in aging yellow rice wine.The differences of main properties were compared and analyzed between the spoilage aging samples and the normal ones. The results showed that the sensory quality of spoilage ones decreased obviously, they were cloudy and sediment, with sour taste, some were even vinegar alike and smelled bad, the content of acid increased while the content of total sugar and alcoholicity,pH decreased. Meanwhile, total bacterial count went beyond the standard greatly.Several selective medium were chosen to detect the microbes, combined with morphological characteristics observation,dyeing and biochemical reactions, 5 Lactobacillus, 4 yeasts (May be Saccharomyces,Hansenula,Pichia,Brettanomyce,respectively) and 4 molds (1 Chromosporeae,1 Aspergillus,2 Penicillium,respectively)were identified.We inoculated these microbes to the sterile wine, then used HPLC to determine the lactic acid content after aging for a period of time. The results showed that lactobacillus MDx,lactobacillus LZY and yeast YJL were the main spoilage microbes that caused the wine corruption, while the rest ones showed no obvious effect.Studies on the temperature resistance,alcohol tolerance and acid resistance of the 3 spoilage strains showed that high alcoholicity(>14%),low-temperature (<15℃) can restrain them effectively,and high acidity(pH<3.8) can restrain the 2 latobacillus effectively. PEF treatment showed that when a 30kV/cm electric field intensity was used to teat for 160μs, the lgS of MDx,LZY,YJL decreased 4.30,4.60,4.89, respectively. Yeast was more sensitive to the PEF treatment than the lactobacillus.