Study On The Flavor Of The Cheese Manufactured With Tibetan Kefir And Active Edible Packaging Films

In order to develop the cheese market in our country and meet consumer?s demand for dairy products, the freeze-dried Tibetan kefir coculture was used as a starter in the production of Camembert-type cheese and Bod ljong cheese. Then the chemical composition, proteolysis, lipolysis, and volatile compounds profile, and microbial diversity were studied during the ripening. At the same time, the effectiveness of antimicrobial edible coatings to Bod ljong cheese was evaluated. Coatings were prepared using chitosan, water chestnut starch and glycerol as a base matrix, together with several combinations of antimicrobial substances-Cornus officinalis fruit extract(COFE), pine needle essential oil(PNEO) and nisin. This article included the following aspects:1) The use of freeze-dried Tibetan kefir coculture as a starter in the production of Camembert-type cheese was investigated. Maturation of the produced cheese was monitored for up to 35 days and the chemical composition, proteolysis, lipolysis, and volatile compounds profile, and microbial diversity were studied. The cheese underwent a significant proteolysis. Palmitic, myristic, oleic, and capric acid were the representative contents of free fatty acids, which rose considerably during ripening. A total of 44 compounds were detected. In headspace of the cheese, the volatile carboxylic acids were the most abundant. A total of 147 bacteria and 129 yeasts were obtained from the cheese during the ripening time.2) The use of freeze-dried Tibetan kefir coculture as a starter in the production of Bod ljong cheese was investigated. The chemical composition, proteolysis, lipolysis, and volatile compounds profile were studied during a 35-day ripening. Bod ljong cheese underwent a great proteolysis and lipolysis. The amount of starter had a significantly effect on the cheese. The speed of cheese proteolysis was in the following order: cheese C > cheese B > cheese A. Glutamic acid, glycine, leucine, phenylalanine, ornithine, lysine, proline were the representative contents of free amino acids, which accounted for about 80 % of the total free amino acids. The volatile compounds of Bod ljong cheese were mainly alcohols and esters.3) A variety of lactobacilli(long and curved, short), yeasts and fibrillar material were observed in the inner portion or out portion of the grain. Kefir grains had a spongy fibrillar structure that was branched and interconnected. Fibrillar material increased progressively towards the interior portions of the grain.4) The film based on mung bean starch-chitosan exhibited higher moisture content, WVP values, ΔE* and less transparency than that based on water chestnut starch-chitosan. The effectiveness of antimicrobial edible coatings to Bod ljong cheese were evaluated throughout 25 d of storage. Coatings were prepared using chitosan, water chestnut starch and glycerol as a base matrix, together with several combinations of antimicrobial substances-Cornus officinalis fruit extract, pine needle essential oil and nisin. Application of coating on cheese decreased water loss, lipid oxidation, headspace gas composition, and colour change. Moreover, the edible coatings with COFE or PNEO had better antimicrobial activity and did not permit growth of microorganism. In the overall acceptability, these cheese were within acceptable ranges by the judgers.