بررسی تغییرات اسیدهای آلی در طول دوره رسیدن پنیرهای سفیر آب نمکی ایرانی با استفاده از مایه های مختلف لاکتیکی

For Iranian fermented cheese processing and ripening, different lactic acid bacteria (LAB) that affect on the physicochemical properties and hence the organoleptic characteristics of the cheese is used. Determination of physicochemical changes of cheese, particularly, organic acids is of importance. In this study five cheese formulas with five different group of cheese starters were processed and ripened in 8% brine during two months at 12±1 °C. HPLC analysis of organic acids were accomplished, using SCR-101H column with U. V. detector at 214 nm and quantified with high purity standards concerning each organic acid recovery. Pyruvic, orotic, citric, propionic, lactic, butyric and acetic acids were analyzed after 1, 10, 20, 30, 40, 50 and 60 days of processing and storage. Each determined organic acid exhibited a specific profile changes during cheese ripening. Lactic acid was dominant organic acid in all samples. Total organic acids were increased significantly after 30 days of storage, but decreased up to the end of ripening. The profile changes of organic acids which was similar in all samples with different amounts related to dominant lactic acid with about 80-90% of the total organic acids. The aromatic mesophile group, CH-N-O1(including Lactococci and Leuconostocs) and Lactobacillus casei and also the mixed mesophiles plus thermophile starters group, CH-1 (including Lactobacillus bulgaricus and Streptococcus salivarius ssp. thermophilus) caused a significant decrease in citric acid and increase in acetic and propionic acid in related cheese samples compared with other cheeses (P < 0.01). But cheese containing only thermophiles or the mixed thermophile and mesophile (code 54) revealed a significant increase in butyric acid. In all samples the changes in pyruvic acid content was irregular. The ripening period of cheese samples were determined by the stepwise regression analysis in relation to their exact amount of organic acids.