Screening Of Lactococcus Lactis Subsp.lactis With Superior Fermentation Characteristics

Lactococcus(L.)lactis subsp.lactis is widely used in industrial production of dairy products,and screening out potential starter strains with superior fermentation characteristics is very important.227 strains of L.lactis subsp.lactis isolated from naturally fermented dairy products in Mongolia,Russia,Inner Mongolia,Qinghai and Yunnan were used for the screening of potential starter strains with superior fermentation characteristics and organoleptic properties.The whole milks were fermented by L.lactis subsp.lactis with inoculum concentration of 106 CFU/ml at 30?,the starter culture R-704 as control group.The fermentation time,physicochemical index and sensory characteristics of fermented milk were monitored and used for screening of strains.Finally,the superior L.lactis subsp.lactis screened in combination with the commercial starter culture YF-L904 were used for fermentation,the main results are listed as follows:(1)The fermentation time and acid-producing rate were used as the indicators of the preliminary screening,40 L.lactis subsp.lactis strains with less than 12 h of fermentation time were screened.(2)The whole milks were fermented by 40 L.lactis subsp.lactis strains,respectively,and then 16 L.lactis subsp.lactis strains with good fermentation properties were screened out.IMAU92143 had the shortest fermentation time,with only 7.59 h.The changes of titratable acidity(? TA)of fermented milk by these five strains were less than 5 T,such as IMAU11822 and IMAU11823.Viscosity of fermented milk by IMAU1 1838 was 1524mPa·s after 24 h storage.The result of the sensory evaluation show that the fermented milk by IMAU1 1823 and IMAU11919 had superior sensory characteristics and special cheese flavor.Specifically,the sensory score of fermented milk samples were 81.57 and 82.36,respectively,and there was no significant difference with that of R-704(p>0.05).The results of GC-MS analysis showed that the special cheese aroma of fermented milk might be related to the higher content of 3-methyl butanol and 3-methyl butyraldehyde.(3)The result showed that fermented milk by the IMAU1191 in combination with YF-L904 has lower acidification level(? TA=23,96°T),and there was no significant difference in the viscosity and retention ability of fermented milk with that of YF-L904(p>0.05),reaching 590mPa·s and 65.29%,respectively.Fermented milk by the IMAU11919 in combination with YF-L904 has higher living cells amount and favorable sensory properties,reaching 8.561 ogCFU/mL and 80.93,respectively,after 21 days of storage.The L.lactis subsp.lactis IMAU11919 has a good potential to be used as starter cultures for industrial application.