Protease Activities Of Semi-Purified Pseudomonas Fluorescens In Protein Degradation Of Pasteurized Milk At Storage

Protein in stored milk spoiled due to protease activities of Pseudomonas fluorescens. To know protease effect in milk, protease activities of semi-purified P. fluorescens in protein degradation of stored pasteurized milk were detected. Protease was semi-purified by ethanol 70 persen. Protease activities were detected by modified Lowry method, protein degradation by formol titration, and protein content by Kjeldahl method. Milk storage’ times were conducted at 0 day (4 days before expired date) up to 12 days (8 days after expired date). The results show that the longer the storage times, the higher the protease activities and protein degradation of milk. At storage 12 days, protease activities in control was 0.2556 Unit/mL (skim) and 0.2116 Unit/mL (whole), and in inoculated milk (crude) was 2.2044 Unit/mL (skim) and 1.5378 Unit/mL (whole); while in inoculated milk (semi-purified) was 3.5355 Unit/mL (skim) and 1.6778 Unit/mL (whole), respectively. The decrease of inoculated milk’ homogeneous were faster than that of control. Protein degradation in control, inoculated skim milk (crude and semi-purified) at 12 days were 4.48 persen, 7.28 persen and 7.62 persen, while that in whole milk were 3.81 persen, 7.28 persen and 6.04 persen, respectively. Based on protease, protein degradation and homogeneous, it can be concluded that skim milk spoiled faster than whole milk. Seminar Nasional Teknologi Peternakan dan Veteriner 2010