ANTI-MICROBIAL, ANTI-BROWNING AND ANTI-MYCOTOXIGENIC ACTIVITIES OF SOME ESSENTIAL OIL EXTRACTS IN APPLE JUICE

摘要

Five essential oils (EO) extracted from lemon grass (Cymbopogon citratus), basil (Ocimum basilicum), rosemary (Rosmariinus officinalis), sage (Salvia officinalis), and clove (Eugenia aromatica), were investigated for their inhibitory effect against polyphenoloxidase (PPO) enzymatic browning, microbial activity, as well as effect on food spoilage and mycotoxin producing fungi, Aspergillus flavus and Aspergillus dchraceus. The TLC technique was used to determine the inhibitory effect of each EO on the radial growth of the fungus, and a dose response of the EO was recorded. Results showed that the EO from lemon grass, clove and rosemary were the most effective and prevented the growth and mycotoxin formation of the two fungi on apple juice when applied at doses of 0.05, 0.2 and 0.3%, respectively. Moderate activity was observed for the EO from basil dose between 0.2% and 0.3%, while the EO from sage was less inhibitory. These effects against food spoilage and mycotoxin producing fungi indicated each essential oil to be a potential food preservative. Also, the results showed that apple juices treated with essential oil (EO) extract from lemon grass, clove and rosemary had a positive effect towards the inhibition of PPO activity and reducing browning as compared to untreated, basil and sage treated juices, at room temperature (25 degrees C) and at refrigerator (4 degrees C), then increased shelf life of apple juice up to 4 weeks. The lowest microbial count for 4 weeks of storage period at VC was observed during the pretreatment of apple juice with lemon grass, clove and rosemary extracts. Therefore lemon grass, clove and rosemary extracts used in the study proved to be efficient extractives against food spoilage and mycotoxin producing fungi and in reducing both the enzymatic browning (PPO) and microbial counts during the preservation of apple juice by refrigeration at 4 degrees C, indicating the potential applicability of each essential oil as a food preservative.