Accelerated ripening of Feta-cheese with freeze-shocked culture of Lactobacillus helveticus or barley extract.

Khaled Meghawry El-Zahar

Food Science Department, Faculty of Agriculture, Zagazig University, 44511 Zagazig, Egypt.

elzahar@hotmail.com, loudarabab@yahoo.fr, khmelzahar@zu.edu.eg

ABSTRACT

         The use of freeze-shocked culture or barley extract as a starter in the production of feta-type cheese was investigated. Maturation of the produced cheese at 4°C was monitored for up to 60 days, and the effects of the starter culture, and the ripening process on quality characteristics were studied. Changes in the physico-chemical and microbiological properties of Feta- cheese were studied throughout 60 days of ripening. Total solid, fat in total solid, titratable acidity, pH, salt in total solid, total nitrogen, water-soluble nitrogen, ripening index, amino were determined. Also, the counts of lactic acid bacteria, yeast, moulds and coliform-bacteria were done. Cheese made from ultra-filtrated retentate incorporated with different levels of either barley at a ratio of 0.05% and 0.1 % or freeze-shocked culture of L. delhrueckii subsp. helveticus at a ratio of 1% and 2%. Addition of barley-extract did not significantly effect on the moisture, fat, total nitrogen or salt content of the resultant cheeses, but significantly increased the acidity contents. Incorporation of the freeze-shocked starter cultures had no significant effects on the gross chemical composition of cheeses. These additives significantly increased the formation of soluble nitrogenous compound, free volatile fatty acids, flavour intensity and improved the body and texture characteristics of Feta cheese. This was more remarkably in cheese made with the increase in the barley extract of freeze of freeze-shocked starter cultures added to ultra-filtrated retentate. Cheeses with added barley extract 0.1% or freeze-shocked starter of L. delhrueckii subsp. helveticus 2% were higher in quality after 15 - 30 days of ripening than the other treatments. Microbial counts during preservation of both types of cheese increased steadily and reached similar levels, with the exception of coliform-bacteria. All types of cheese produced with freeze-shocked culture or barley extract as a starter were approved and accepted by the panel during the preliminary sensory evaluation compared to commercial feta- cheese.