Study On Enhancement Of Buttery Flavor Of Cheddar Cheese Based On Diacetyl

As a hard cheese, the unique "cheddaring" process of Cheddar cheese gives it a unique texture and functional properties, and makes it the largest imported cheese currently in China. Because of the preference of Chinese consumers to buttery flavor of cheddar cheese, the development of cheddar cheese with buttery flavor would be desirable for the consumers. Studies have showed that diacetyl contributes to buttery flavor in cheese, but during ripening the diacetyl content in cheese continues to decline and even gets completely exhausted. Only a few studies were conducted on the enhancement of buttery flavor of cheddar cheese through adjunct culture with high production of diacetyl. Therefore, this study intended to enhance the buttery flavor of cheddar cheese, through the screening of adjunct culture of cheddar cheese with high production of diacetyl, and explore the impact of the selected strains on cheese flavor.Firstly, 14 commercial cheddar cheeses exported from 4 countries with different ripening ages were investigated by descriptive sensory evaluation and GC-MS, which illustrated the flavor characteristics of different cheddar cheeses. Consumer preferences of the diacetyl content were further analyzed through principal component analysis and cluster analysis. The results showed that the flavor of different commercial cheddar cheese varied, and the cheddar cheese flavor characteristics were mainly buttery, creamy, sulfur, acid, nutty, brothy, maturity, et al. Cheddar cheese flavor varied with different ripening time, with buttery and creamy for young cheese, and sulfur, acid, brothy, nutty for aged cheese. In addition, the aged commercial cheese samples typically showed low diacetyl content and were generally ranked low for buttery sensation as well.Because of the consumer preference for buttery flavor, a screening model of adjunct culture for high production of diacetyl was developed according to the metabolic pathways of diacetyl, and α-acetolactate decarboxylase, diacetyl reductase, acetoin reductase were chosen for selection of culture with high production of diacetyl, together with the growth ability of the strains in cheese ripening environment, acidifying ability, and autolysis degree. In total 23 lactic acid bacteria were screened and variation was observed among the strains for autolysis degrees, acidifying abilities, and production of diacetyl, α-acetolactate decarboxylase, diacetyl reductase and acetoin reductase activitities. Among the strains, CCFM 601 had high production of diacetyl and low enzymes activities; CCFM 44 had high production of diacetyl and high enzyme activities; CCFM 412 had low production of diacetyl and low enzyme activities; CCFM 309 had low production of diacetyl and high enzyme activities. Considering these indexes, CCFM 601 showed the highest potential as adjunct culture of cheddar cheese to enhance buttery flavor.The impact of four selected adjunct culture with different diacetyl production and enzyme activities was evaluated with a rapid ripening model by determining the basic physical and chemical properties, the degree of protein hydrolysis, microbial changes, texture, and volatile flavor compounds and sensory sensation of cheddar cheese. The results showed that between the basic physical and chemical indicators, proteolysis, texture of the four cheddar cheese with added adjunct culture had no significant difference. Compared to the other groups, diacetyl content and buttery flavor was higher in the cheddar cheese with CCFM 601, and the decline of diacetyl is slower as well. Experimental results showed that the CCFM 601 increased the diacetyl production and enhanced buttery flavor of the cheese.To further verify the effect of CCFM 412(B1), CCFM 309(B2), and CCFM 601(B3) on Cheddar cheese, the three cultures with different diacetyl production and enzyme activities were used to produce Cheddar cheese and ripened at 8℃, with a humidity of 85% for 5 months. The results showed the diacetyl content of B1 was higher than that of B2 after one month, and diacetyl of B2 decreased faster than that of B1 during ripening. The diacetyl content of B3 was higher than that of B1 and B2, and the buttery flavor of B3 was higher than that of B1 and B2, which verified the usefulness of the screening indexes.The results verified the correctness of the screening model of high production of diacetyl of adjunct culture of cheddar cheese. Therefore, the selected strain CCFM 601 with production of diacetyl, low activity of α-acetolactate decarboxylase, diacetyl reductase, and acetoin reductase have the potential for application in cheddar cheese to enhance the buttery flavor.