Insect lipid profile: aqueous versus organic solvent-based extraction methods

Effect of Different Drying Methods on Nutrient Quality of the Yellow Mealworm (Tenebrio molitor L.)

Yellow mealworm (Tenebrio molitor L.) represents a sustainable source of proteins and fatty acids for feed and food. Industrial production of mealworms necessitates optimized processing techniques, where drying as the first postharvest procedure is of utmost importance for the quality of the final product. This study examines the nutritional quality of mealworm larvae processed by rack oven drying, vacuum drying or freeze drying, respectively. Proximate composition and fatty acid profile were comparable between the dried larvae. In contrast, larvae color impressions and volatile compound profiles were very much dependent on processing procedure. High-temperature rack oven drying caused pronounced darkening with rather low content of volatiles, pointing toward the progress of Maillard reaction. On the other hand, vacuum drying or freeze drying led to enrichment of volatile Maillard reaction and lipid oxidation intermediates, whose actual sensory relevance needs to be clarified in the future. Beyond sensory and visual importance drying intermediates have to be considered with regard to their metal ion chelating ability; in particular for essential trace elements such as Zn²⁺. This study found comparable total zinc contents for the differently dried mealworm samples. However, dried larvae, in particular after rack oven drying, had only low zinc accessibility, which was between 20% and 40%. Therefore, bioaccessibility rather than total zinc has to be considered when their contribution to meeting the nutritional requirements for zinc in humans and animals is evaluated.

Insect Oil as An Alternative to Palm Oil and Poultry Fat in Broiler Chicken Nutrition

Simple Summary

Recently, there has been increasing interest in the use of insects as an alternative sustainable source of protein and fat in animal feed to improve animal production and maintain ecological sustainability. Palm oil is commonly used in broiler chicken nutrition; however, due to the environmental footprint, consumers have formed negative opinions regarding its applications. Therefore, alternatives to palm oil are urgently needed. The present study was conducted to evaluate the effects of Tenebrio molitor oil as a total replacement for palm oil and poultry fat in broiler chicken diets on chicken performance, nutrient digestibility, pancreatic enzyme activity, various blood parameters and lipid fatty acid compositions of liver and breast muscle tissues. Based on the obtained results, T. molitor oil did not show any adverse impacts on performance and improved the fatty acid profiles of liver and breast muscle tissues. In conclusion, T. molitor oil may be a sustainable alternative to palm oil in broiler chicken nutrition.

Abstract

This study was conducted to evaluate the effects of Tenebrio molitor (TM) oil as a total replacement for palm oil and poultry fat in broiler chicken diets on growth performance, nutrient digestibility, pancreatic enzyme activity, selected blood parameters and the lipid fatty acid compositions of liver and breast muscle tissues. A total of 72 seven-day-old female Ross 308 broiler chickens were used. The birds were randomly distributed into three groups with 12 replicates each, using two birds per replicate for 30 days in metabolic cages. The basal diet was supplemented with 5% palm oil, poultry fat or TM oil. There was no effect (p > 0.05) caused by the dietary oil replacement on the birds’ performance and apparent nutrient digestibility. Liver size (p = 0.033), the concentration of hepatic triglycerides (p = 0.049) and total cholesterol (p = 0.048) were reduced by TM oil supplementation. Furthermore, TM oil supplementation increased n-3 and n-6 fatty acids (p = 0.006; p < 0.001, respectively) in breast muscle tissue. In conclusion, the use of TM oil in broiler chickens’ diets did not show any adverse effects on performance, nutrient digestibility and blood biochemical parameters. Moreover, TM oil supplementation improved the fatty acid profiles of liver and breast muscle tissues.

Nutritional value, protein and peptide composition of edible cricket powders

There are various indicators, including FAO and EU sources, that edible insects could become one of the solutions to the problem of global food supply. This report was aimed at improving the knowledge on powdered crickets (Acheta domesticus). The analyses of the basic nutritional composition revealed that cricket powders were rich in protein (42.0-45.8% of dry matter) and fat (23.6-29.1% of dry matter). In terms of mineral content, CPs were rich in Ca, Mg and Fe. Most of all, the levels of Cu, Mn and Zn were especially high (2.33-4.51, 4.1-12.5, 12.8-21.8 mg/100 g of dry matter, respectively). Furthermore, the analyses into the proteins indicated that the cricket powders were treated with high temperatures and allowed the determination of four cricket-specific peptides that showed sufficient thermostability to serve as markers for authentication.

Effect of sex on the nutritional value of house cricket, Acheta domestica L

Since January 2018, insects have been recognised as novel foods in the EU, but their nutritional value varies, and factors affecting their nutritional composition have been debated. We investigated the effect of sex on the nutritional value and chemical composition of the house cricket (Acheta domestica L.). Both sexes were rich in protein and lipids. The proximate composition was partly influenced by sex; females contained a significantly higher amount of lipids (18.3-21.7 vs 12.9-16.1 g/100 g dry matter, p = 0.0001) and fewer proteins than males (61.2-64.9 vs 66.3-69.6 g/100 g dry matter, p = 0.0001). Males contained more chitin (p = 0.0015) and nitrogen chains (p = 0.0003) than females. Only the ash (p = 0.4314) and nitrogen-free extract (p = 0.4871) were uninfluenced by sex. Furthermore, nutrient quality expressed as essential amino acid (72.3-77.1), thrombogenicity (1.22-1.45), and atherogenicity indices (0.53-0.58) did not differ between sexes (p > 0.05).

Beetle (Ulomoides dermestoides) fat improves diabetes: effect on liver and pancreatic architecture and on PPARγ expression

Ulomoides dermestoides is a beetle traditionally consumed to treat diabetes. In this study, we performed a composition analysis of U. dermestoides to obtain the principal fractions, which were used to assess the effect on glycemia, liver and pancreatic architecture, and PPARγ and GLUT4 expression. Normal mice and alloxan-induced diabetic mice were administered fractions of chitin, protein or fat, and the acute hypoglycemic effect was evaluated. A subacute study involving daily administration of these fractions to diabetic mice was also performed over 30 days, after which the liver and pancreas were processed by conventional histological techniques and stained with hematoxylin and eosin to evaluate morphological changes. The most active fraction, the fat fraction, was analyzed by gas chromatography-mass spectrometry (GC-MS), and PPARγ and GLUT4 mRNA expressions were determined in 3T3-L1 adipocytes. The protein and fat fractions exhibited hypoglycemic effects in the acute as well as in the 30-day study. Only the fat fraction led to elevated insulin levels and reduced glycemia, as well as lower intake of water and food. In the liver, we observed recovery of close hepatic cords in the central lobule vein following treatment with the fat fraction, while in the pancreas there was an increased density and percentage of islets and number of cells per islet, suggesting cellular regeneration. The GC-MS analysis of fat revealed three fatty acids as the major components. Finally, increased expression of PPARγ and GLUT4 was observed in 3T3-L1 adipocytes, indicating an antidiabetic effect.

Suitability of microwave drying for mealworms (Tenebrio molitor) as alternative to freeze drying: Impact on nutritional quality and colour

Freeze drying represents the current practice to stabilize mealworms, even though it is an energy demanding technique. Therefore, it was examined in the present study whether microwave drying could be a proper alternative. To this end, the impact of both drying techniques on the proximate composition, vitamin B₁₂ content, fatty acid profile, oxidation status and colour parameters of mealworms was investigated. Furthermore, the influence of the application of vacuum during microwave drying was studied. The different drying technologies resulted in small differences in the proximate composition, while the vitamin B₁₂ content was only reduced by microwave drying. The fat fraction of freeze dried mealworms showed a higher oxidation status than the fat of microwave dried mealworms. Application of a vacuum during the microwave drying process did not appear to offer advantages. This research shows that for mealworms microwave drying can be a proper alternative to freeze drying.

Composition of black soldier fly prepupae and systematic approaches for extraction and fractionation of proteins, lipids and chitin

Black soldier fly (BSF, Hermetia illucens) constitutes an economic way to convert residual biomasses into a valuable source of biomolecules, such as proteins, lipids and chitin. The present investigation was undertaken to evaluate the feasibility of applying different extraction protocols, either chemical extractions or enzymatic assisted extraction, to recover pure fat, protein and chitin fractions. First, exact proximate composition, total amino acids, fatty acids profile, and N-acetylglucosamine content of the prepupae samples were determined. BSF prepupae biomass contained, expressed on dry weight, 32% proteins, 37% lipids, 19% minerals, 9% chitin. The lipid fraction was easily recovered by organic solvents, while the most challenging issue was the separation of protein from chitin. The best separation was obtained by alkali extraction of proteins (96% of protein recovered) albeit with loss in their integrity as indicated by the measurement of the degree of hydrolysis with the o-phthaldialdehyde method. To avoid protein damage in alkali media, a stepwise protein extraction adopting milder conditions was also explored based on Osborne fractionation method, allowing the recovery of >85% of BSF high purity and high quality proteins, and the obtainment of chitin-enriched fraction as well. The possibility of using an enzymatic assisted extraction of proteins was also explored, obtaining a maximum nitrogen solubilisation in the best case (with Bacillus licheniformis protease) of about 60%. In this latter case, the chitin fraction obtained also had a significant residual protein content.

Nutritional Potential of Selected Insect Species Reared on the Island of Sumatra

Inhabitants of the Indonesian island of Sumatra are faced with the problem of insufficient food supplies and the consequent risk of undernourishment and health issues. Edible insects as a traditional and readily available food source could be part of the solution. The nutritional value of insects depends on many factors, e.g., species, developmental stage, sex, diet, and climatic conditions. However, edible insects bred in Sumatra for human consumption have never before been assessed with regard to their nutritional value. Our study involved analyses of crude protein, chitin, fat and selected fatty acid contents of giant mealworm larvae (Zophobas morio), larvae of the common mealworm (Tenebrio molitor) and nymphs of the field cricket (Gryllus assimilis). Crude protein content in the samples ranged from 46% to 56%. Highest (35%) and lowest (31%) amounts of fat were recorded in giant mealworm larvae and larvae of the common mealworm, respectively. Chitin amounts ranged from 6% to 13%. Based on these values, which are comparable to those known from other food insects reared in different regions of the world, the edible species bred in Sumatra could become food sources with a potential to help stave off hunger and undernourishment.

Nitrogen-to-Protein Conversion Factors for Three Edible Insects: Tenebrio molitor, Alphitobius diaperinus, and Hermetia illucens

Insects are considered a nutritionally valuable source of alternative proteins, and their efficient protein extraction is a prerequisite for large-scale use. The protein content is usually calculated from total nitrogen using the nitrogen-to-protein conversion factor (Kp) of 6.25. This factor overestimates the protein content, due to the presence of nonprotein nitrogen in insects. In this paper, a specific Kp of 4.76 ± 0.09 was calculated for larvae from Tenebrio molitor, Alphitobius diaperinus, and Hermetia illucens, using amino acid analysis. After protein extraction and purification, a Kp factor of 5.60 ± 0.39 was found for the larvae of three insect species studied. We propose to adopt these Kp values for determining protein content of insects to avoid overestimation of the protein content.

Dietary fatty acids influence the growth and fatty acid composition of the yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae)

Fat is the second most abundant component of the nutrient composition of the mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) that represents also an interesting source of PUFA, especially n-6 and n-3 fatty acids, involved in prevention of cardiovascular diseases. This study investigated the possibility of modifying the fat content and the FA composition of yellow mealworms through feeding and how this would be influenced by developmental stages, pupal sex, and generation with the future aim of applying this coleopteran as a diet supplement for human health. Growth rate and cumulative mortality percentage on the different feeding substrates were also evaluated to select the optimal conditions for a mass-raising of this insect species. Despite the different fat content in the six different breeding substrates used, T. molitor larvae and pupae contained a constant fat percentage (>34% in larvae and >30% in pupae). A similar total fat content was found comparing larvae and male and female pupae of the second generation to those of the first generation. On the contrary, FA composition differed both in larvae and pupae reared on the different feeding substrates. However, the exemplars reared on the diets based on 100% bread and 100% oat flour showed SFA, PUFA percentages, and an n-6/n-3 ratio more suitable for human consumption; the diet based on beer yeast, wheat flour, and oat flour resulted in a contemporary diet that most satisfied the balance between a fat composition of high quality and favorable growth conditions.

Does selective logging stress tropical forest invertebrates? Using fat stores to examine sublethal responses in dung beetles

The increased global demand for tropical timber has driven vast expanses of tropical forests to be selectively logged worldwide. While logging impacts on wildlife are predicted to change species distribution and abundance, the underlying physiological responses are poorly understood. Although there is a growing consensus that selective logging impacts on natural populations start with individual stress-induced sublethal responses, this literature is dominated by investigations conducted with vertebrates from temperate zones. Moreover, the sublethal effects of human-induced forest disturbance on tropical invertebrates have never been examined. To help address this knowledge gap, we examined the body fat content and relative abundance of three dung beetle species (Coleoptera: Scarabaeinae) with minimum abundance of 40 individuals within each examined treatment level. These were sampled across 34 plots in a before-after control-impact design (BACI) in a timber concession area of the Brazilian Amazon. For the first time, we present evidence of logging-induced physiological stress responses in tropical invertebrates. Selective logging increased the individual levels of fat storage and reduced the relative abundance of two dung beetle species. Given this qualitative similarity, we support the measurement of body fat content as reliable biomarker to assess stress-induced sublethal effects on dung beetles. Understanding how environmental modification impacts the wildlife has never been more important. Our novel approach provides new insights into the mechanisms through which forest disturbances impose population-level impacts on tropical invertebrates.

Safety aspects of the production of foods and food ingredients from insects

At present, insects are rarely used by the European food industry, but they are a subject of growing interest as an alternative source of raw materials. The risks associated with the use of insects in the production of foods and food ingredients have not been sufficiently investigated. There is a lack of scientifically based knowledge of insect processing to ensure food safety, especially when these processes are carried out on an industrial scale. This review focuses on the safety aspects that need to be considered regarding the fractionation of insects for the production of foods and food ingredients.

Feed Conversion, Survival and Development, and Composition of Four Insect Species on Diets Composed of Food By-Products

A large part of the environmental impact of animal production systems is due to the production of feed. Insects are suggested to efficiently convert feed to body mass and might therefore form a more sustainable food and/or feed source. Four diets were composed from by-products of food manufacturing and formulated such as to vary in protein and fat content. These were offered to newly hatched Argentinean cockroaches, black soldier flies, yellow mealworms, and house crickets. The first two species are potentially interesting as a feed ingredient, while the latter two are considered edible for humans. Feed conversion efficiency, survival, development time, as well as chemical composition (nitrogen, phosphorus, and fatty acids), were determined. The Argentinean cockroaches and the black soldier flies converted feed more efficiently than yellow mealworms, and house crickets. The first two were also more efficient than conventional production animals. On three of the four diets yellow mealworms and house crickets had a feed conversion efficiency similar to pigs. Furthermore, on the most suitable diet, they converted their feed as efficiently as poultry, when corrected for edible portion. All four species had a higher nitrogen-efficiency than conventional production animals, when corrected for edible portion. Offering carrots to yellow mealworms increased dry matter- and nitrogen-efficiency and decreased development time. Diet affected survival in all species but black soldier flies, and development time was strongly influenced in all four species. The chemical composition of Argentinean cockroaches was highly variable between diets, for black soldier flies it remained similar. The investigated species can be considered efficient production animals when suitable diets are provided. Hence, they could form a sustainable alternative to conventional production animals as a source of feed or food.

Growth performance and feed conversion efficiency of three edible mealworm species (Coleoptera: Tenebrionidae) on diets composed of organic by-products

Insects receive increasing attention as an alternative protein-rich food source for humans. Producing edible insects on diets composed of organic by-products could increase sustainability. In addition, insect growth rate and body composition, and hence nutritional quality, can be altered by diet. Three edible mealworm species Tenebrio molitor L., Zophobas atratus Fab. and Alphitobius diaperinus Panzer were grown on diets composed of organic by-products originating from beer brewing, bread/cookie baking, potato processing and bioethanol production. Experimental diets differed with respect to protein and starch content. Larval growth and survival was monitored. Moreover, effects of dietary composition on feed conversion efficiency and mealworm crude protein and fatty acid profile were assessed. Diet affected mealworm development and feed conversion efficiency such that diets high in yeast-derived protein appear favourable, compared to diets used by commercial breeders, with respect to shortening larval development time, reducing mortality and increasing weight gain. Diet also affected the chemical composition of mealworms. Larval protein content was stable on diets that differed 2-3-fold in protein content, whereas dietary fat did have an effect on larval fat content and fatty acid profile. However, larval fatty acid profile did not necessarily follow the same trend as dietary fatty acid composition. Diets that allowed for fast larval growth and low mortality in this study led to a comparable or less favourable n6/n3 fatty acid ratio compared to control diets used by commercial breeders. In conclusion, the mealworm species used in this study can be grown successfully on diets composed of organic by-products. Diet composition did not influence larval protein content, but did alter larval fat composition to a certain extent.

TiO₂/SiO₂ core-shell composite-based sample preparation method for selective extraction of phospholipids from shrimp waste followed by hydrophilic interaction chromatography coupled with quadrupole time-of-flight/mass spectrometry analysis

A solid-phase extraction (SPE) procedure, using titania-coated silica (TiO2/SiO2) core-shell composites as the sorbent, combined with a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for extraction, visualization, and quantification of phospholipids in shrimp waste (Litopenaeus vannamei). The SPE protocol was optimized, and the best conditions were pH 5 of the loading solvent, 10% aqueous methanol as the washing solvent, and 1.0 mL of chloroform/methanol (1:2, v/v) as eluting solvents. Afterward, the eluate was separated on a diol hydrophilic interaction chromatography (HILIC) column. A total of 69 phospholipid species were identified and determined. The results indicated that, in comparison to previously published methods, this strategy was cost-effective and efficient in extraction, characterization, and determination of phospholipids. Meanwhile, phospholipids were abundant in shrimp waste, most of which contained unsaturated fatty acyl chains, such as 18:3 [α-linolenic acid (ALA)], 20:5 [eicosapentaenoic acid (EPA)], and 22:6 [docosahexaenoic acid (DHA)]. The successful application of this strategy paves the way for full use of traditionally discarded shrimp wastes.