ZHUMAO JIANG (1), Guangtian Zhou (2), Jingwei Geng (2), Xinxia Ge (2)
(1) Science and Engineering College of Chemistry and Biology, Yantai
University, Shandong, China; (2) Shandong Provincial Key Laboratory of
Microbial Engineering, Shandong Institute of Light Industry, Jinan,
Shandong, China
Spent yeast slush is the by-product of brewing, the yield of which is
about 1.5% of total beer production. The yeast is separated from the
spent yeast slush which can be utilized generally, while the rest of the
waste beer can be used as raw material to produce beer vinegar.
However, it’s difficult to maintain the abiotic stability of it as
goods. In the present report, we studied the abiotic turbidity of beer
vinegar. The waste beer was treated with enzymolysis, heat treatment,
and clarification so as to enhance the abiotic stability. We also
studied the technological parameters of mixed bacteria fermentation
which could improve the beer vinegar flavor. biotic turbidity is a key
factor that affects the quality of beer vinegar. The appearance of
abiotic turbidity is associated with the high content of
high-molecular-weight protein and polyphenols. Papainase was used to
deal with the waste beer at the optimal condition: zymolyzing
temperature was 55°C, zymolyzing time was 120 min, and enzyme dosage was
4,000 U/g. Then the liquid was heat-treated by high temperature. The
optimal conditions included boiling temperatures of 100°C, carrageenan
addition of 60 mg/L, and heat treating time of 50 min. After
fermentation, the beer vinegar was clarified with PVPP which could
reduce the polyphenols further. The flavor is another factor which has
an impact on the quality of the beer vinegar. Aroma-producing yeast
xjb45 was pitched together with Acetibacteria AS1.41 as mixed
fermentation in order to improve the aroma of the beer vinegar, which
could provide the metabolic pathway of the flavor substances as well as
the enzymes needed. The optimal conditions of beer vinegar fermentation
included the ratio of AS1.41 to xjb45 of 1:1.5, fermentation temperature
of 30°C, and inoculum of 15%. The beer vinegar prepared by this
technique was of improved flavor with the characteristics of malt and
apple, and it also had a good abiotic stability. This way to utilize the
waste beer from spent yeast provided by our study could effectively
reduce environmental pollution.
Zhumao Jiang, associate professor of food fermentation engineering,
doubles as director of the Food Fermentation Engineering Survey Section
in the Yantai University Science and Engineering College of Chemistry
and Biology. Zhumao obtained his bachelor degree in food engineering
from Wuxi Institute of Light Industry (now Jiangnan University) in 1982
and worked in the Huaiyin Industrial College (now Huaiyin Institute of
Technology), teaching and researching food microbiology and brewing
technology. From 1995, he worked in the Yantai University Science and
Engineering College of Chemistry and Biology, teaching and researching,
in turn, fermentation technology and bioengineering equipment in
bioengineering, food fermentation technology, and food additives in food
science engineering. He is a member of the Chinese Society for
Microbiology and a council member of the Chinese Institute of Food
Science and Technology Branch for lactic acid bacteria.
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