Reduction of Shelf-life of Dairy Products by a Heat-stable Protease from Pseudomonas Fluorescens P26

Abstract

Butter, Cheddar cheese, cottage cheese, vanilla ice cream mix, and homogenized milk were manufactured from milk or components of milk containing heat-stable protease or a culture of Pseudomonas fluorescens P26 which produces this protease. Effects of protease on keeping quality were determined by comparisons to controls without protease. Comparisons were on results of the Hull test for measurable proteolysis and, also, on sensory analyses by panel evaluations. No significant differences in quality were observed on butter, ice cream mix, or milk which was repasteurized at 63 C for 30 min. Protease (or bacteria) was added 12 h before manufacture. Proteolysis was significant in Cheddar cheese made from milk containing .94 unit of enzyme per milliliter. Flavor scores were significantly lower in cheese made from milk containing the protease than in the control cheese. The protease (.86 unit/ml) produced significant proteolysis in cottage cheese but not as much as P. fluorescens P26. Flavor was adversely affected by both treatments. © 1973, American Dairy Science Association. All rights reserved.