Is under-vacuum packaging a suitable method for Hermetia illucens and Tenebrio molitor larvae storage?

The use of insects in food and feed needs a robust knowledge of their nutritional properties, but also of the many aspects related to their preservation for maintaining, as long as possible, these features. This study aimed to evaluate the effect of non- or under-vacuum storage on the quality preservation of Hermetia illucens (HI) and Tenebrio molitor (TM) dried mature larvae. These insects were reared on vegetable wastes (HI) and wheat bran (TM) in a lab-scale facility. Three samples (15 g each) of HI and TM dried larvae were taken to be analyzed, from non-vacuum and under-vacuum bags stored for 1, 3, and 6 months from drying (T1, T3, T6, respectively). Proximate composition, total lipids, fatty acid profile, primary (conjugated dienes, CD), and secondary (thiobarbituric acid reactive substances, TBARS) products of lipid oxidation were analyzed. In addition, biogenic amines analysis was carried out. Two different one-way ANOVAs were performed with R Core Team (2022) for each species to estimate the effect of the treatment and the effect of the storage time. The most interesting results, expressed on 100 g of dried sample, involved lipid oxidation metabolites and biogenic amine formation. In the first case, from a time perspective, HI prepupae from T6 had a significantly higher content of CD (1.98 mmol Hp/100 g) than T1 and T3 groups, whilst TM samples showed major content of TBARS in the T1 group (1.59 mg MDA/100 g). On the other hand, biogenic amine content was higher in HI under-vacuum than in the non-vacuum samples, especially cadaverine, histamine, and spermidine (119.0, 14.8, and 13.8 mg/100 g, respectively). Moreover, tyramine production has been detected notably in T3 HI prepupae (179.35 mg/100 g). About treatment, no significant difference was found in TM, neither in proximate composition nor in amine formation; however, time-wise, cadaverine was detected most in the T6 group (6.13 mg/100 g), while putrescine, tyramine, and spermidine were mostly present in the T3 samples (16.02, 20.5, and 10.68 mg/100 g, respectively). Hence, vacuum treatment did not seem to preserve the product quality of HI, nor significant advantages were identified for TM. Thus, further investigations are required to deepen insect storage to provide a clear picture of their safe use as food and feed ingredients.