Processing of Larvae of Alphitobius diaperinus and Tenebrio molitor in Cooked Sausages: Effects on Physicochemical, Microbiological, and Sensory Parameters

Proteins from insect production represent an interesting (environmentally friendly) option or supplement to commercial livestock farming. At present, however, the larval stages of <i>T. molitor</i> (mealworm) and <i>A. diaperinus</i> (buffalo worm) have been authorized as food for human consumption EU-wide, as have the nymph and adult stages of <i>Locusta</i> (<i>L.</i>) <i>migratoria</i> (<i>Locusta migratoria</i>, Linnaeus, 1758) and <i>Acheta</i> (<i>A.</i>) <i>domesticus</i> (house cricket, <i>Acheta domesticus</i>, Linnaeus, 1758). However, there is the problem that insects that are recognizable as a whole tend to be avoided by consumers, especially in the European region, as they are reminiscent of living things and can cause aversion and disgust in consumers. Against this background, in the present study, five batches of two types of cooked sausages were produced: on the one hand, with turkey, and on the other hand, with pork lean meat as a base. In different formulations, 10% and 20% of the meat contents (turkey or pork) in these meat products were replaced by deep-frozen, pulverized <i>T. molitor</i> and <i>A. diaperinus</i> larvae. The effects of the addition of these insects in the products on the microbiological and physicochemical parameters of these cooked sausages, compared to a product without insect content, directly after heating, were investigated. After production, a storage trial was also carried out to determine whether possible insect ingredients could influence the growth of inoculated bacterial species (<i>Bacillus</i> (<i>B.</i>) <i>cereus</i>, <i>Escherichia</i> (<i>E.</i>) <i>coli</i>, <i>Listeria</i> (<i>L.</i>) <i>monocytogenes</i>, <i>and Campylobacter</i> (<i>C.</i>) <i>jejuni</i>) and how the addition of insect larvae affectsthe sensory and physicochemical properties during storage. The study showed that the products with insects had reduced lightness (turkey <i>p</i> C = 0.025), increased yellowness (pork <i>p</i> S = 0.0009, <i>p</i> C < 0.0001 and turkey <i>p</i> C = 0.0027) and a reduced red color (pork <i>p</i> S < 0.0001, <i>p</i> C = 0.0001) after heating when compared to the cooked sausages without insects. However, no significant differences between the various cooked sausages with or without insects in terms of cooking loss, firmness, and protein, ash, and fat or water contents were found. The microbiological tests showed, on the one hand, that the prior microbial reduction (e.g., in the form of blanching) of the insect larvae was essential in order to guarantee the flawless microbiological quality of the cooked sausages and, on the other hand, that the addition of insects to the cooked sausages did not significantly affect the growth of the inoculated bacterial species and that no sensory differences could be detected during storage. Despite the significant color effects on the product, <i>A. diaperinus</i> and <i>T. molitor</i> larvae would be suitable as protein or meat alternatives in cooked sausages, but they would have to undergo pre-treatment, primarily with regard to microbiological safety. The extent to which a complete replacement of meat is possible has to be investigated in further studies.