Studies on preparation and use of bovine pepsin from adult cattle Abomasa as rennet substitute for small scale cheese processing
Loading...
Date
1999
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
World-wide shortage of rennet has stimulated interest in the search for rennet
substitutes. In order to overcome the scarcity and high price for rennet in
Tanzania, studies on preparation of a rennet substitute from cattle abomasa were
undertaken in three experiments
Experiment one dealt with investigations into the optimisation of pepsin extraction
conditions i.e. on regions of abomasa, extraction of dry versus fresh material, drying
methods, ionic strength, extraction pH, temperature, time, activation pH and
clarification methods. Results showed that the fundic region, sundrying, 10% salt,
extraction with HCL at pH 3 fbr 3 days, at 37° C, activation pH 2 fbr 30 min and
clarification using NazHPC^.H?。produce an extract with maximum milk clotting
activity (MCA). Optimum conditions were applied to extract pepsin with dilute HCL,
vinegar and lemon juice. Vinegar (VP) and HCL (HP) gave better yield, shelf-life,
proteolytic activity, chymosin:pepsin ratio, microbial quality and formagraph
characteristics than lemon juice. Concentrating VP extract lead to greater loss in
MCA than for HP extract.
In experiment two, HP extract was purified by DEAE cellulose chromatography, gel
filtration, mono Q and phenyl sepharose chromatography. Studies on the purified
enzyme with regard to formagraph characteristics, molecular mass, sodium
dodecylsulphate gel electrophoresis (SDS-PAGE) and N-terminal amino acid
sequence showed that pepsin was homogenous with fold purification of 366,
recovery rate of 32.7%,Ill
Specific activity 3920 MCA (units/mg), molecular mass 34,500 Da. The N-terminus
of purified pepsin contained no lysine and the MCA decreased with enzyme purity.
In experiment 3, HP and VP extracts were mixed with rennet at 0, 25, 50, 75, 100%
and used for making three types of cheese. Renneting time (RT) for cheese milk,
butterfat (%BF) and total nitrogen (%TN) in whey, chemical composition and
microbial quality of cheese samples obtained at different storage time intervals,
sensory evaluation at maturity and overall quality assessment were determined. RT
and TN losses increased with level of pepsin; chemical composition of all cheese
types were significantly different (Pv.001). The pH in SUA Pastafilata and SUA
Alpine and TN in Tilsiter cheese were not significantly different (P>0.05). Sensory
evaluation was not significantly different (P>0.05) in smell, taste, appearance and
bitterness, however, bitterness in SUA Pastafilata and appearance in SUA Alpine
were significantly different (P<0.05); appearance in SUA Pastafilata and village
Alpine were significant different (P<0.01). Bitterness, taste in SUA Alpine and
bitterness in Tilsiter cheeses were highly significant different (P<.001). Overall
quality assessment of cheese did not show significant differences (P>0.05).
Therefore all enzyme combinations were suitable for all types of cheese implying
that pepsin was an appropriate rennet substitute.
Description
Thesis
Keywords
Bovine pepsin, Cheese processing, Adult cattle, Pepsin extraction, Rennet Substitute