Progression Of Acidification Research Articles

DETERMINATION OF pH CHANGE KINETICS DURING DIFFERENT STAGES OF KASHAR CHEESE MANUFACTURING FROM RAW AND PASTEURIZED MILK WITH ADDITION OF THERMOPHILIC, MESOPHILIC AND MIXED THERMOPHILIC CULTURE

ABSTRACT The pH change kinetics during Kashar cheese production from raw and pasteurized milk with addition of thermophilic, mesophilic and mixed thermophilic‐mesophilic lactic acid bacteria were evaluated. The kinetics of pH change were determined during milk ripening, cooking/holding and pressing/fermentation phases of Kashar cheese. The pH decreased logarithmically, nonlinearly, with time in the milk ripening period, and reduced linearly with time in the cooking/holding and pressing/fermentation stages. Pasteurization of milk retarded the rate of change in pH during the three periods. The highest rate of pH change was determined in the addition of thermophilic culture, followed by mixed thermophilic‐mesophilic and then mesophilic ones during milk ripening. The pH change characteristics of cheese made with thermophilic starter were similar to the cheese made with mixed thermophilic‐mesophilic culture, but different from mesophilic lactic acid bacteria during cooking/holding and pressing/fermentation stages. PRACTICAL APPLICATIONSOne of the important factors in the control of cheese quality is the extent of acid production in the vat. Acid development at a desired rate is important during cheese making. The progress of acidification is monitored by pH change in the industrial Kashar cheese production. Three main stages have been recognized with respect to pH change: milk ripening, cooking/holding and pressing/fermentation. This study evaluated and compared the pH change kinetics during various stages of Kashar cheese making using raw, pasteurized milk with the addition of thermophilic, mesophilic and mixed thermophilic culture. This work may help in the comparison of raw and pasteurized milk, and in the selection of appropriate starter culture for Kashar cheese production.

EVALUATION OF pH CHANGE KINETICS DURING DIFFERENT STAGES OF KASHAR CHEESE PRODUCTION FROM BOVINE, OVINE AND CAPRINE MILK

ABSTRACT The objective of this study was to determine the pH change kinetics during Kashar cheese production from bovine, ovine and caprine milk. Kinetics of pH change were determined during milk ripening, cooking/holding and pressing/fermentation phases of Kashar cheese. The pH decreased logarithmically, nonlinearly, with time in the milk ripening period and was reduced linearly with time in the cooking/holding and pressing/fermentation stages. The time of pH decrease in cow's, ewe's and goat's milk was significantly different, except cooking/holding time, for three stages. There was no difference between bovine and caprine milk in cooking/holding time; however, ovine milk was significantly different from the other two kinds of milk. The shortest and the longest overall times were determined for caprine and ovine milk cheeses, respectively. The rate of change in milk pH of the three species was significantly different for three stages. The rate followed the pattern caprine > bovine > ovine milk. PRACTICAL APPLICATIONS Optimum acid development is essential to creating the desired cheese mass. For each major cheese type, lactic acid must develop in the appropriate time, usually not too rapidly or too slowly, and in a specific concentration. The progress of acidification is monitored by pH change in the industrial Kashar cheese production. The final pH of cheese is determined not only by the amount of lactic acid but also by the buffering capacity (BC) of the milk and curd. However, the BC is different between milk species. This study evaluates and compares the pH change kinetics during various stages of Kashar cheese making using cow's, ewe's and goat's milk. This work may help to compare milk and cheese curds made from bovine, ovine and caprine milk.

Fertilization of spruce monocultures in the territory of Training Forest Enterprise in Kostelec nad Černými lesy

Long-term fertilization effects were evaluated including NPK, Ca and N applications at the lower altitudes. The studied localities are in the territory of Training Forest Enterprise in Kostelec nad Černými lesy, at an altitude of 300–500 m a.s.l., sites of beech-oak-fir types. Fertilizers were used in 1965–1967, the evaluation of soil condition was done in 1967 (before fertilization) and 2002. After 25–35 years, only low effects of fertilization are detectable in the humus forms and complex soil profile – surface humus accumulation, soil chemistry, as well as nutrient contents. Complex fertilization was reflected in higher site fertility in general, N-fertilization only in the progress of acidification. During the period 1967–2002, a strong general trend of acidification is obvious caused by both acid deposition and Norway spruce monoculture-based forestry.

The ultrasonic properties of skim milk related to the release of calcium from casein micelles during acidification

Milk samples were acidified with different amounts of glucono-δ-lactone (GDL) and samples of permeates were collected rapidly by ultrafiltration at intervals during acidification. Calcium contents of these sera were measured to define the extent and rate of dissociation of micellar calcium phosphate. In parallel samples, measurements were made of the ultrasonic velocity and the ultrasonic attenuation of milks and permeates. This allowed the establishment of a complete profile of the changing mineral distribution of milk and changes in ultrasonic properties, as functions of pH. The results showed that changes in both of ultrasonic parameters depended almost completely on changes in composition of milk serum, and that states of casein micelles made little contribution. This makes ultrasound an excellent method for following the release of calcium and the progress of acidification in milks.