Development of predictors for macadamia kernel deterioration
This study examined the capacity of existing chemical indices and accelerated shelf-life testing (ASLT) protocols to identify the least stable consignments at delivery. To do this the oxidative stability of premium and commercial grade kernel retained from the visual assessment of commercial nut-in-shell consignments of macadamias were investigated. Initial rancidity test were made on extracted oil for peroxide value (PV), % free fatty acids (FFA), conjugated dienes (CDHP), and p-anisidine value (pAV). A single 50 g subsample was taken and repeated hexanal measures were made on the same jars after storage at accelerated shelf-life testing (ASLT) conditions of 0, 2, 4 and 6 weeks when the trial was terminated and kernel assessed with the same initial suite of rancidity measures. There was no correlation between visual quality assessments and any of the measures kernel rancidity before or after ASLT. Initial PV and FFA values were also only weekly related to final ASLT results indicating minimal potential to manage kernel quality. All other measures, CDHP and pAV were not or only weakly related the hexanal level at week 6. By comparison the correlation between hexanal at week 0 and hexanal at week 6 was R2=0.556 and by week 2 this increased to significant to R2=0.921, (P<0.016). Kinetic models indicate that storing kernel for 6 weeks ASLT conditions was equivalent to 6 months at ambient (20°C). Our results indicate that the response to 6 weeks ASLT can be predicted after two weeks and this may be reduced by optimizing the ASLT conditions.
McConchie, C., Yang, A., Forrester, R. and Salter, B. (2016). Development of predictors for macadamia kernel deterioration. Acta Hortic. 1120, 363-368
storage, accelerated aging, rancidity, hexanal, nut