| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1998: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
Casein is a phosphoprotein, and dephosphorylated proteins/peptides are hydrolysed at a faster rete by lactococcal proteinases/peptidases than phospholylated proteins or peptides. The combined action of protcinase/peptidases and phosphatases may be important for cheese quality, In preliminary work, the acid phosphatases (AP) from skim milk (SM-I and SM-II), butter milk (BM) and of the cell membrane (CM) and cell wall (CW) of Lactococcus lactis ssp lactis 303 were purified of partially purified.
1. Acid phosphatase from Lactic acid bacteria
Activities of CM and CW were optimal at pH 5.2-5.5 and 50℃. The heat stability of the enzymes differed : the CM enzyme was more stable. The enzymes released inorganic phosphate from the mixture of casein phosphopeptides but did not dephosphorylate casein.
2. Acid phosphatase from milk
The heat stability of the enzymes differed ; the SM enzyme was more stable, with a D-value of 60 min at 75℃, while the BM enzyme had a D-Value of 10 min. at 75℃. It was suggested the presence of isozymes of acid phosphatase in whole milk, located in the skim milk or asociated with the BM.
3. Bchaviour of Acid phosphatase in Cheddar cheese ripening.
The proteinase/peptidase related more peptides and amino acids from the phosphopeptides which had been dephosphorylated by the AP from SM-II or CM.
The AP activity in the water-soluble fraction of Cheddar cheese which had been made using strain 303 as starter, deercased slightly during ripening but the total AP activity and that in the water-insoluble fraction increased slightly. The APs SM-II and CM, which were present in water-insoluble fraction, seemed to contribute to the dephosphorylation on phosphopeptides during Cheddar cheese during ripening.
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