INFLUENCE OF PACKAGING MATERIAL AND STORAGE TIME ON PHYSICAL, CHEMICAL AND MICROBIOLOGICAL PROPERTIES OF SET YOGURT: A COMPARATIVE STUDY BETWEEN MODIFIED BIODEGRADABLE POLY(LACTIC ACID) AND POLYPROPYLENE

Abstract

The current paper investigates the influence of storage time and type of polymeric packaging material on the chemical, physical and microbiological properties of set yogurt. Firstly, poly(lactic acid) (PLA) was modified by using a core-shell rubber (CSR) and an acrylic processing aid (PA) to produce PLA with high toughness and good processability. Secondly, an appropriate PLA/PA/CSR composition was selected and fabricated to yogurt cup. The yogurt was stored in both modified PLA and polypropylene (PP) packages to observe some physical, chemical and biological changes. Finally, the biodegradation test was made on both packages and compared with that cellulose. Experimental results revealed that adding 5wt% CSR gave PLA/PA as tough as PP. Types of packaging material and storage time did not change the color of yogurt. The number of lactic acid bacteria grew significantly after they had been incubated for 6 days. The bacterial viability decreased dramatically due to the increased acidity and the decreased pH. A positive impact on the viability of bacterial growth was found when yogurt was stored in modified PLA package. This made yogurt had more health benefits than stored in PP package. The biodegradation test results indicated that the modified PLA degraded at a rapid rate. It achieved approximately 50% biodegradation within 40 days which was comparable to the time required to degrade the cellulose, whereas PP was non-biodegradable over the period studied. In summary, substitution conventional PP by a novel modified PLA seems to be a better way for both the health and the environment benefits.

Keywords

• Biodegradable polymer
• Food quality
• Set yogurt
• Biodegradation