Factors influencing the almond kernel breakage during shelling processes and the impact of water conditioning on kernel color and free acidity

Kernel breakage is the major economic challenge for the Spanish almond industry. Thus, this study aimed to determine the kernel breakage during the shelling operation by (ii) identifying the primary breakage factors, and (ii) evaluating the impact of water conditioning on final kernel quality. Twelve almond samples, of which 9 intraspecific hybrids were specially selected to enlarge the variability range. Kernel breakage ranged between 5 and 71%, with HYB8 registering the lowest breakage values and HYB5 the highest. Cultivars, ‘Vairo’, ‘Guara’, and ‘Lauranne’ showed also substantial breakage rates (40, 45, and 56 %). More absorbed water ( r = −0.71∗∗), elasticity ( r = −0.60∗), wider ( r = −0.70∗) and rounder ( r = −0.65∗) fruit with higher fat content ( r = −0.84∗∗∗), reduced breakage in shelling operation. Meanwhile, almonds with a higher shell strength ( r = 0.63∗), more elongated ( r = 0.67∗), with higher skin ( r = 0.69∗) and fiber content ( r = 0.58∗) were more susceptible to breakage. Water conditioning produced a color change in kernel, while the oil acidity was similar before and after (0.1%) the conditioning process, meaning that, this was fast and correct enough to avoid enzymatic degradation. In the absence of significant technological advancements, further research must focus on optimizing water conditioning processes and standardizing cultivars to reduce kernel breakage in the Spanish almond industry. • Almond water conditioning prior to shelling is essential to reduce kernel breakage. • Moisture and fat increase kernel elasticity and reduce kernel breakage in shelling. • Wider and rounder almonds suffer minimal breakage in Spanish shelling machines. • Harder, elongated almonds with more skin and fiber content break easily in shelling. • Water conditioning affects kernel color, but not free acidity of oil.