Effect of nonthermal processing methods on microbial content and physiochemical properties of Australian honey

Abstract

Honey is known for its therapeutic properties owing to its antioxidant and antibacterial activity. However, the presence of microbes and other undesirable matters in raw honey makes it a subject for processing. Consequently, the current thermal processing, negatively affects the physiochemical, antioxidant and antibacterial properties of honey. In the current research, high-pressure processing was explored as an alternative non-thermal technique for honey processing. Six raw Australian honey samples were subjected to high-pressure processing at 400 and 600 MPa for 10 and 15 min. The effectiveness of high-pressure processing in microbial reduction and its effects on honey physiochemical, antioxidant and antibacterial properties were studied and compared with the thermally processed honey samples at 60, 70 and 80 oC for 10, 20 and 30 min. High-pressure processing significantly (p<0.05) reduced the microbial load of honey. High-pressure processing at 600 MPa for 15 min attained a similar microbial count reduction that was attained by thermally processed honey at 80 oC for 30 min. No significant (p<0.05) changes were observed in the physiochemical properties of honey samples high-pressure processed at 400 MPa. However, at 600 MPa, detrimental changes were observed in the physiochemical properties (colour, HMF content and diastase activity) of honey. Variable changes were also observed in the antioxidant properties of high-pressure processed honey at 600 MPa. High-pressure processing caused an increase in the antibacterial activity of honey against gram-negative bacteria, whereas no significant (p<0.05) changes were observed against gram-positive bacteria. In contrast, thermal processing caused detrimental effects on the physiochemical, antioxidant and antibacterial properties of honey, which was evident from decreased diastase activity, increased HMF content, and decreased antioxidant and antibacterial activity. From the results, it was evident that the changes in the physiochemical, antioxidant and antibacterial activity of honey samples were dependent on the type of honey.

Date of Award	2023
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Vijay Jayasena (Supervisor)