Date Published: February 1, 2019
Publisher: Public Library of Science
Author(s): Andrea Roncolini, Vesna Milanović, Federica Cardinali, Andrea Osimani, Cristiana Garofalo, Riccardo Sabbatini, Francesca Clementi, Marina Pasquini, Massimo Mozzon, Roberta Foligni, Nadia Raffaelli, Federica Zamporlini, Gabriele Minazzato, Maria Federica Trombetta, Anse Van Buitenen, Leen Van Campenhout, Lucia Aquilanti, Karol Sestak.
In the present study, inclusion of mealworm (Tenebrio molitor L.) powder into bread doughs at 5 and 10% substitution level of soft wheat (Triticum aestivum L.) flour was tested to produce protein fortified breads. The addition of mealworm powder (MP) did not negatively affect the technological features of either doughs or breads. All the tested doughs showed the same leavening ability, whereas breads containing 5% MP showed the highest specific volume and the lowest firmness. An enrichment in protein content was observed in experimental breads where the highest values for this parameter were recorded in breads containing 10% MP. Breads fortified with 10% MP also exhibited a significant increase in the content of free amino acids, and especially in the following essential amino acids: tyrosine, methionine, isoleucine, and leucine. By contrast, no differences in nutritional quality of lipids were seen between fortified and control breads. Results of sensory analyses revealed that protein fortification of bread with MP significantly affected bread texture and overall liking, as well as crust colour, depending on the substitution level. Overall, proof of concept was provided for the inclusion of MP into bread doughs started with different leavening agents (sourdough and/or baker’s yeast), at 5 or 10% substitution level of soft wheat flour. Based on the Technology Readiness Level (TRL) scale, the proposed bread making technology can be situated at level 4 (validation in laboratory environment), thus suggesting that the production of breads with MP might easily be scaled up at industrial level. However, potential spoilage and safety issues that need to be further considered were highlighted.
Bread is a staple food throughout Europe and western countries; it is obtained from the baking of a leavened dough commonly prepared with wheat flour, water, and a leavening agent, with or without the addition of salt (sodium chloride) and other ingredients (e.g. malt, enzymes, animal fats, oils, hydrogenated fats, margarine, sugars, milk powder, bread improvers, stabilizers, etc.). Among the leavening agents, different alternatives can be used, including: (i) chemicals (e.g. sodium bicarbonate); (ii) baker’s yeast, which essentially consists of Saccharomyces cerevisiae biomass; and (iii) sourdough. The latter consists of a mixture of flour and water spontaneously fermented by (or inoculated with) a mixed population of lactic acid bacteria (LAB) and yeasts and propagated by back-slopping . The use of the sourdough leads to the production of bread with enhanced sensory and nutritional traits as well as an extended shelf-life . Western white bread produced with wheat flour is usually rich in carbohydrates that represent about 50% of dry weight (w/w), whereas its protein content is generally very low, with average values generally comprised between 6 and 8% (w/w) [3, 4], thus rendering bread as an ideal candidate for protein fortification. The World Health Organization (WHO) and the Food and Agricultural Organization of the United Nations (FAO) have defined fortification as “the practice of deliberately increasing the content of an essential micronutrient, ie. vitamins and minerals (including trace elements) in a food irrespective of whether the nutrients were originally in the food before processing or not, so as to improve the nutritional quality of the food supply and to provide a public health benefit with minimal risk to health”.
Among edible insects, mealworm larvae are easy to rear and can provide protein of high nutritional value [76, 77]. In some EU countries (e.g., the Netherlands), the farming of mealworms is already a profitable activity that can benefit from innovative exploitation processes . In the present study, proof of concept was provided for the inclusion of MP into bread doughs leavened with sourdough and/or baker’s yeast. Results overall collected indicated that bread fortification with MP at the 5 and 10% of the soft wheat flour amount significantly affected breads properties depending on fortification level. As a general trend, an improvement of the protein and amino acid contents of the fortified breads was seen. Moreover, MP contributed to the improvements in both bread volume and softness, likely due to its lipid fraction. At this regard, MP appears as an adequate ingredient for bread fortification. Whereas technically, there are no major limitations to incorporate MP into bread dough at the assayed levels (5 and 10%), some considerations regarding microbial and sensory quality traits of bread enriched with mealworm powder can now be made. First, acceptability of fortified breads was negatively affected by comparison with control breads produced with the sole soft wheat flour. However, if overall liking scores collected in the present study were compared with those of a previous research from the same laboratory on breads fortified with cricket powder (at 10 and 30% substitution level), mealworm breads were characterized by a higher acceptability, feasibly due to the acknowledged differences in flavor and aroma of mealworm and cricket powders. Concerning the microbial quality, the occurrence of spore-forming bacteria in both doughs and breads fortified with mealworm powder highlighted potential spoilage and even human safety issues that still need to be resolved. At this regards, in future studies, it might be valuable to investigate the effect of strategies to reduce the amount of endospores in bread and, more in general, in baked leavened goods, such as the use of preservatives, e.g. propionate  or mitigation technologies, e.g. dehydration  or toasting .