Edible Insect Meals as Bioactive Ingredients in Sustainable Snack Bars

Abstract

Insect metabolites are known for their preservative potential, but the time-consuming and unsustainable extraction process compromises their transferability. This study aimed to identify user-friendly solutions based on the use of insect meals that could improve microbiological safety as well as consumer acceptability. In this regard, the antimicrobial activity of Alphitobius diaperinus and Tenebrio molitor meals against surrogate strains of Gram-positive (Listeria monocytogenes) and Gram-negative (Escherichia coli) pathogenic bacteria and mycotoxin-producing fungi (Penicillium expansum) was evaluated. Minimum inhibitory concentration values of between 3.12 mg/mL vs. Listeria innocua and 12.50 mg/mL vs. Escherichia coli were found. Based on this finding, a model food was developed also considering consumer acceptance. Statistical analysis of food preferences showed that nutritional and sustainability claims were the independent variables of greatest interest. Therefore, waste or by-products from other food chains were selected as co-ingredients for sustainability, nutritional, and sensory claims. Analysis of the chemical composition showed that the insect bar-style snack qualifies as a "high-protein" food, as protein provides more than 20% of the energy value. Based on the moisture (30%) and water activity (0.77) values, the bar could be classified as an intermediate-moisture food. The challenge test showed that the insect meal prevented the proliferation of intentionally added undesirable microorganisms. Conclusively, the findings complement the knowledge on the antimicrobial activities of insect meals, offering new possibilities for their use as natural preservative ingredients with nutritionally relevant properties.

Keywords: Alphitobius diaperinus; Escherichia coli; Listeria; Penicillium expansum; Tenebrio molitor; antimicrobial activity; biopreservation.

Figure 1

Sequence of photos relating to snack-bar preparation: (a) insect meals (in upper bowl) and other ingredients (in lower bowl); (b) cutting of formed and shaped dough; (c,d) finished product.

Figure 2

Inhibition halo plot (mm) of Alphitobius diaperinus (green) and Tenebrio molitor (yellow) meals against Escherichia coli ATCC 8739, Listeria innocua ATCC 33090, and Penicilliium expansum ATCC 36200. Different letters indicate a significant difference between microorganisms based on the statistical ANOVA test. Asterisks indicate significant difference values (*, p < 0.05; **, p < 0.01; ***, p< 0.001) in attributes among the 3 microorganisms.

Figure 3

Box-and-whisker plots showing the antimicrobial score produced by A. diaperinus meal, T. molitor meal, chitin, and larvae extract against Escherichia coli ATCC 8739 (blue), L. innocua ATCC 33090 (green), and P. expansum ATCC 36200 (red). Different letters with the same color indicate significance difference between microorganisms depending on different treatments (larvae extract, chitin, insect meals) based on the statistical ANOVA test.

Figure 4

Predictive model of the propensity to consume insect-based foods by multiple linear regression of several variables, including consumers age as well as sustainability and nutritional claims. The size of the bubbles is directly related to the expectation of nutritional claims; the color of the bubbles (purple, yellow) is related to the expectation of nutritional claims on a scale of 1 to 10.

Figure 5

Part of the whole graph shows the preference for insect-based food types.

Figure 6

Bar plot showing the acceptability level (9-point hedonic scale) of sensory attributes in samples from conventional (control) and insect-based snack bars. Different letters indicate significant differences in attributes between the batches. Statistical tests were carried out using a t-test.

Figure 7

Maximum growth rate (m_max) of fungi (presumably Penicillium), Listeria, and Escherichia in insect-based or conventional (control) snack bars intentionally inoculated with a pathogen surrogate microorganism cocktail.