Effects of milk preservation using the lactoperoxidase system on processed yoghurt and cheese quality

Abstract

The lactoperoxidase system (LP-system) is an acceptable chemical method for raw
milk preservation, especially in rural areas where refrigeration facilities are absent to
farmers. Milk production in most African countries is dominated by small-scale
traditional production systems using low yielding local breeds. Therefore, processors
who operate in such situations must rely on small volumes of milk from many
farmers. Application of the LP-system prolongs the shelf life of raw milk and also
encourages grouping of farmers hence facilitating milk collection by processors. The
application of the LP-system is a recent preservation method for milk in Cameroon
whose efficiency has been proven. Therefore, need arose for further studies on the
influence of this method on milk processing as well as the quality dairy products.
The LP-system was activated by adding 10 ppm sodium thiocyanate and 8.5 ppm
sodium percarbonate to fresh milk. Yoghurt and Bambui cheese were processed
separately from treated and untreated (control) milk samples. Yogurt was produced
from both the treated and the control milk samples at 2%, 3%, 4% and 5% (v/v)
culture levels. Yogurt samples were analysed for acidity, protein content and dry
matter content while cheese was analysed for butterfat and moisture content.
Statistical tests were conducted by Analysis of Variance using the Fisher's test.
Simple organoleptic assessments were conducted to compare yogurt and cheese from
the treated and the control milk. Activation of the LP-system delayed lactic acid
formation in yogurt during incubation and storage leading to increased energy
consumption during processing and an improved keeping quality during storage. LPsystem
treatment reduced the overall organoleptic quality of yogurt while it improved
on that of Bambui cheese. Dry matter content and fat content of yogurt were not
significantly affected by LP-system treatment (P<0.05). LP-system treatment did not
also affect the moisture and fat content of cheese but slightly improved on its yield.

Keywords: Cheese, lactoperoxidase system, milk, yogurt

AJFAND Vol. 8 (3) 2008: pp. 358-374