An in vitro method to assess protein and amino acid digestibility of black soldier fly (BSF) larvae meals was optimized and evaluated. The assay consisted of acid and alkaline hydrolysis of a partially defatted BSF larvae meal (BSF0). The optimization was performed using a fractional factorial design of 32 experiments, testing 7 factors at two levels each. Highest digestibility values were obtained when pH of the stomach and intestine were 2 and 9, reaction time in the stomach and intestine were 1h and 4h, concentration of enzyme in the stomach and intestine were 1U and 7U, at 37°C. Subsequently, the above condition (experiment 11) was used to evaluate; (i) different production batches of the same BSF meal and (ii) differently processed BSF meals. Different batches of the same BSF meal had overall the same AA digestibility, therefore ensuring a level of reproducibility. Differences between differently processed meals showed highest digestible protein in BSF 4 (32.88 ± 0.15) and BSF 5 (33.91 ± 0.08), corresponding to defatted BSF protein meal and BSF protein meal, respectively. Whole larvae BSF meal (BSF 6) had the lowest digestible protein value (27.03 ± 0.45).
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