Manuka honey in New Zealand is known for its superior antimicrobial and antioxidant properties. However, these valuable properties are known to be compromised when raw honey goes through conventional thermal processing, thus reducing its final quality. As such, this present work is undertaken to assess the effect of high-pressure processing on quality of honey, namely, the antioxidant activity, colour and viscosity. The honey was subjected to different pressures (200400 MPa) at ambient temperatures (25 to 33 "C) and combined with moderate temperatures (53 to 74 "C) for holding times (10 to 30 min). Thermal processing (49 to 70 "C) was also carried out for comparison purpose. In the absence of heat, the antioxidant activity of high-pressure processing (HPP)-treated samples (600 MPa, 10 min) was found to increase by about 30 % with no colour changes detected. The shear-thinning behaviour of the honey was also retained after HPP at ambient temperature, whereas for combined HPP-thermal treatment, no added benefit in antioxidant activity was observed particularly at higher temperature. Colour was significantly degraded when processed for 215 min at 70 "C and the flow behaviour was brought about from shear thinning to Newtonian. Thus, it can be concluded that the quality of honey can be enhanced by using high-pressure processing at ambient temperature.

SummaryThis work was undertaken to assess the effects of high-pressure processing on brown pigment formation, antibacterial activity and hydroxymethylfurfural (HMF) content in Manuka honey. Thus, high-pressure processing has no adverse effect on the honey quality because it can control HMF concentration during process. Increasing brown pigment formation is associated with the enhancement of antibacterial activity.

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