Investigation of Different Post-Harvest Treatments on the Quality of Almond Kernels during Ambient Storage

Maintaining almond kernel quality during and after harvest is crucial in producing premium kernel product for Australian and international markets. In this study, we investigated the effects of different post-harvest treatments on changes in moisture content, texture, colour, nutritional profile and flavour of almond kernels over a storage period of 9 months under ambient conditions. Post-harvest treatments included steam pasteurization, volumetric heating pasteurization, oven roasting and dry roasting, which were compared with raw kernels. Moisture and texture analysis revealed that the average values within each treatment group did not change significantly over 9 months, although the breaking force required to create an initial crack in the kernel structure were markedly lower for Steam Pasteurized (SP) and Oven Roasted (OR) samples after 9 months. Sensory analysis conducted by a trained panel of experts revealed that the chewiness of raw samples increased over time, and both toasted and roasted characteristics were low. For OR and Dry Roasted (DR) samples the chewiness was low and roasted and toasted properties were higher. Average overall enjoyment score given to samples as a part of sensory testing was higher for Volumetric Heating Pasteurization (VHP) and DR at start of the storage (control) and stayed higher than others after 6 and 9 month of storage. Testing of nutritional content of samples showed changes in alpha tocopherol content in roasted samples. However, DR samples had higher content in comparison with OR samples. Volumetric heating treatment didn’t diminish tocopherol content of samples in comparison with raw samples while the average alpha tocopherol content of SP over first 3 month of storage was lower. Both SP and OR samples showed lower fat percentage in comparison with raw, VHP and DR. A reduction was observed in Lightness (L*) values for all samples tested. Among the tested treatments OR samples had darker kernels and Raw and VHP samples had lightest colours. The testing results showed the potential of volumetric heating pasteurization and roasting in maintaining quality of kernel over bulk storage period.