Statistical modelling of sensory, physical, and chemical changes in almonds during prolonged storage at different conditions: Effect of shelling on shelf life

Raw ‘Nonpareil’ and ‘Butte’ almonds were stored both inshell, and as shelled kernels, for up to 24 months in varying temperature and percent relative humidity (% RH) storage environments. Almonds were sampled randomly every 2 mo and analyzed for peroxide values (PVs), percent free fatty acids (% FFAs), moisture contents (MCs), water activity (a_w) and crunchiness. PVs > 2.0 milliequivalents of active O₂ kg⁻¹ oil, or a crunchiness reading which deviated > 15% from baseline values (at day 0), triggered consumer acceptance panels (n ≥ 85) to occur. Consumer acceptance panels, which would later become in-house panels because of COVID-19, dictated whether a sample continued in the study. Linear regressions were developed to model the change in PVs, % FFAs, MCs and a_w of stored samples throughout the storage period or until a sample was removed from the study. Based on regression slopes, storing almonds inshell provided greater oxidative and hydrolytic stability in almond kernels. For example, at 10 months, inshell nuts had PV = 0.895 compared to 1.41 meq. O₂ kg⁻¹ oil for shelled nuts, and FFA values of 0.186 versus 0.332%. Multivariate models confirmed that inshell storage was the most predictive factor for limiting quality changes, while % RH was a less dominant factor, and temperature played a minor role in % FFA and a_w changes. Finally, while almond crunchiness varied, this appeared to be mostly independent of storage conditions, but was primarily influenced by cultivar.