Effect of different freezing methods on the lipid stability of Brazil nuts from different origins

Introduction: Brazil nuts are a product of high nutritional value, relevant to the Amazon bioeconomy, rich in unsaturated lipids and susceptible to degradation. In this context, freezing emerges as a conservation alternative, and it is necessary to evaluate how different freezing rates may influence their stability during storage. Objective: To evaluate the effects of slow and quick freezing on the lipid stability of Brazil nuts after 180 days of storage. Methodology: Brazil nuts in the shell from Rio Preto da Eva and Beruri, Amazonas, Brazil, were subjected to slow (−18°C) and quick (−25°C) freezing, respectively. Analyses were performed at time zero and after 180 days of storage, evaluating water activity (Aw), acidity index, and peroxide index (AOAC, 2016) as indicators of physicochemical and lipid stability. Data were analyzed using Student’s t-test and two-way ANOVA (p ≤ 0.05). Discussion: Freezing rate influenced the evaluated parameters. Aw decreased from 0.96 to 0.76 under slow freezing (p < 0.001), indicating changes in water availability associated with ice crystal formation, whereas it remained stable under quick freezing (0.97; p = 0.374), suggesting greater structural preservation. The acidity index did not change under slow freezing (1.24 to 1.55mg KOH/g; p = 0.442), but increased under quick freezing (1.86 to 3.29mg KOH/g; p = 0.011). The peroxide index decreased under slow freezing (p < 0.001), with no change under quick freezing (p = 0.950), indicating differences in stages of the oxidative process. In both cases, acidity and peroxide values remained below the limits established by ANVISA (4.0mg KOH/g and 15 mEq/kg, respectively), and the Codex Alimentarius, indicating adequate preservation. Conclusion: Both treatments promoted adequate preservation, maintaining product quality, meeting regulatory limits, and highlighting the potential of freezing as an innovative preservation strategy, with flash freezing standing out as the most efficient alternative.