Optimising macadamia kernel processing for shelf-life (MC06010)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Freshly roasted macadamia kernels were highly desired for their unique flavour and texture. The capacity to reliably deliver this experience to consumers was proving a challenge. The Australian macadamia industry was striving to find reliable diagnostic measurements linked to processing and consumer perception of kernel quality. This project examined the effects of kernel moisture content, roasting and storage duration on kernel deterioration using accelerated shelf-life testing (ASLT). This information was used to develop kinetic models to describe the effects of temperature and storage duration on kernel deterioration. This information was a key element for the future development of a system for the prediction of shelf-life of macadamia products. In the interim the ASLT was used to detect kernels with low oxidative stability in commercial consignments as they posed greatest threat of alienating consumers. The ASLT was able to simulate the effects of 6 months storage in 6 weeks, and the outcome from these ALST trials could be predicted within two weeks. In controlled research trials little or no change in kernel composition was observed with this treatment where as less than half of the commercial samples were within acceptable product specifications after this time. This indicated a widespread problem throughout the Australian macadamia industry. It was found that there was no relationship between oxidative stability after 6 weeks of ASLT and the visual assessment of kernel quality showing there was limited capacity to manage kernel shelf-life at the time. The variation in oxidative stability within consignments was very large so significant difference between consignments was detected. Development of sampling protocols and quality control procedures were required to manage oxidative stability commercially. In these investigations there were significant cultivar and kernel moisture content effects that needed to be understood to prevent confounding this issue.