Acid phosphatases activity in cheese and starters.

Area of Science:

• Food Science
• Enzymology
• Dairy Chemistry

Background:

• Acid phosphatase plays a role in cheese ripening and flavor development.
• The origin and contribution of acid phosphatase from milk versus starter cultures in cheese remain areas of investigation.

Purpose of the Study:

• To investigate the stability of acid phosphatase activity in Greek and Cheddar cheeses during extended storage.
• To determine the contribution of starter organisms to acid phosphatase activity in Cheddar cheese.
• To characterize the properties of acid phosphatase from starter cultures and compare it with milk-origin enzyme.

Main Methods:

• Assayed acid phosphatase activity in Greek and Cheddar cheeses after 18 and 12 months of storage, respectively.
• Isolated and characterized acid phosphatase from Streptococcus cremoris-lactis NCDO 762 starter cultures, determining optimal pH, inhibitors, and kinetic parameters (Km).
• Compared the properties of starter-derived acid phosphatase with that isolated from bovine milk and present in Cheddar cheese.

Main Results:

• Acid phosphatase activity was unaffected by storage in both Greek and Cheddar cheeses.
• Starter organisms contributed insignificantly to acid phosphatase activity in Cheddar cheese.
• The enzyme from starter cultures was high molecular weight, particle-bound, with optimal activity at pH 5.2, and inhibited by various agents. Casein was a poor substrate.
• Acid phosphatase in Cheddar cheese was primarily of milk origin, with minor modifications due to bound peptides from cheese maturation.

Conclusions:

• The primary source of acid phosphatase activity in cheese is the milk-origin enzyme, not the starter cultures.
• The stability of acid phosphatase activity suggests its role in long-term cheese characteristics.
• Understanding enzyme origins is crucial for controlling cheese ripening and quality.