| China is a main country in the world for apple producing. A large number of fallen and substandard fruits need to be treated every year. Apple vinegar is a new type of product developed form apple utilization. It not only has the preventive and hygienical effectiveness of ordinary vinegar, but also has high nutritional value, and rich of vinegar and fruit fragrance, besides as condiment, it can also use for beverage, health goods, and cosmetic and skin care products production. Therefore, apple vinegar production will be a viable means for fallen and substandard fruits utilization. There are many methods for apple vinegar brewing, The speed of solid-state fermentation is slow, but can get a good quality vinegar; liquid fermentation is faster, but the quality of its products is generally poor; vinegar brewed by immobilized cell fermentation is also generally poor, but the prominent features of this brewing method is easy to realize continuous processing, and the quality of products from different batch is homogeneous. The aim of this work was to combine the characteristics of the aforesaid three vinegar brewing methods, and develop a new type of apple vinegar brewing method to solve the contradiction between the quality of product and the speed of fermentation. The main research conclusions in this study showed as follow:(1) The optimum conditions for microorganism immobilization while sodium alginate as a carrier was keep the concentration of calcium chloride at 0.05 mol / L, concentration of sodium alginate at 6%, and add a small amount of 6% gelatin in sodium alginate (6% alginate sodium:6% gelatin = 9.0:1.0).(2) The stability of microorganism immobilized particles made by sodium alginate was fine. Fermentation performance of immobilized Saccharomyces cerevisiae 1450 was not significant decline for use of 17 times (17days) or store under low temperature (4℃) for six weeks. And fermentation performance of immobilized acetic acid bacteria AS1.41 was not significant decline for continuous use four times (28 days), and still maintain a certain intensity for store under low temperature (4℃) for a month.(3) Apple vinegar with good quality can obtain at the end, when multi-microorganisms co-immobilized particles with a ratio of strains of Saccharomyces cerevisiae 1450, 60%, aroma-improving yeast AS2.300, 30%,and lactic acid bacteria, 10 % was used for alcohol fermentation,. But, when multi-microorganisms co-immobilized particles of Saccharomyces cerevisiae 1450 and acetic acid bacteria AS1.41 was used for apple vinegar brewing, the fermentation performance can not be keep for a long time.(4) The optimal process conditions for apple vinegar brewing by co-immobilized technology while 250 mL flask as fermentation vessels was keep inoculate amount at 15%, fermentation temperature at 30℃and initial pH at 4.0 in alcoholic fermentation stages; and keep inoculate amount at 10%, alcohol concentration at 5.0%, fermentation temperature at 32℃, shaker speed betwwen 180 to 200 r/min and loaded liquid volume at 80 mL in acetic acid fermentation stages.(5) In addition to improving the velocity of fermentation, the multi-microorganisms co-immobilization technology developed in this study also can improving the quality of apple vinegar. The amount of unvolatile acids and amino-state N in apple vinegar produced by this type of technology was more than apple vinegar produced by liquid fermentation technology and immobilization technology and the composition of flavor components was similar to apple vinegar produce by solid-state fermentation technology. Only 24 hours was needed for alcoholic fermentation, and seven days for acetic acid fermentation in amplification test, the fermentation rate was greater than reported in the literature.(6) Qin-guan and Fuji were suitable for apple vinegar brewing. |
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