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Insects are an excellent nutritional food source
There is very little doubt that entomophagy can be an important solution in decreasing malnutrition in developing countries, but it may also help to improve health in Western societies. As insects are high in mono- and poly-unsaturated fatty acids, intake of insect products instead of conventional livestock products may have positive health effects.
Many insects are an excellent nutritional food source with regard to fat and protein, and they have been found to be a rich source of vitamins and minerals, especially iron and zinc. Iron deficiency is the world’s most common nutritional disorder. This condition not only occurs in developing countries but also in Western societies. Many insects have a high iron content, even higher than red meat, and entomophagy could therefore be recommended from that perspective. If red meat consumption is reduced in the future, as recommended by many health organizations, iron deficiency could become even more common than it is now unless appropriate substitutes are used.
The chemical composition of insects depends on many factors and may differ significantly even in the same developmental stage of one species. For example, the studies of wild insects show both seasonal variation as well as variations between different populations of the same species living in the same general area.
Nutrient content may also differ in commercially farmed species of insects. Moreover, the content of substances varies in adults and their larvae. For instance, adult beetles of T. molitor and Z. atratus contained more protein than the literature values reported for their larval counterparts, and one-half to one-third of the fat content of their larval stages.
Insect processing methods affects their nutrient potential, for instance changes in the protein digestibility and the vitamin content. Depending on the processing conditions, heat processing may reduce or increase digestibility. Studies have shown that solar drying at 30°C of the toasted sample led to a much higher loss (64%) in the riboflavin content as compared to the fresh dried sample (46%).
This trend was also observed for all other vitamins on the test samples under similar processing conditions. The rate of the vitamin destruction is accelerated by an increase in temperature and duration of heating. Therefore, optimal processing methods need to be investigated even as we promote the commercialization of these insects.
Insects show a wide range of caloric content, as the following table shows:
Insects are potentially an important energy efficient source of protein for humans, either through a direct consumption or as food supplements for stock (poultry, pigs and aquaculture) and many nations have already been using it.
For example, local communities in the Amazon region attain 8% – 70% of their dietary protein from insects and several other invertebrates such as spiders and earthworms. However, there are large differences in protein sources.
Developed nations have a higher protein consumption per capita than developing nations – about 96 g/person/ day – but a much greater proportion of it is derived from meat (65%). The protein consumption in developing countries is much less – about 56 g/person/day and a still lesser portion (only 25% of it) is animal protein.
The protein content varies by species of insects, but generally is of a good quality and high digestibility. Analyses showed that in egg, larva, pupa and adult stages, the raw protein content is generally 15% – 81% on a dry basis.
The protein content of some insects is also higher than that of chicken eggs, meat and fowl. The content of essential amino acids is 10% – 30% of all amino acids (35% – 50%). The protein digestibility of insect protein
is reported at values of 77% – 98%, especially after removing the exoskeleton. This is only slightly lower than the values reported in other animal protein sources (egg 95%, beef 98% and casein 99%).
Whole dried bees had a digestibility of 94.3% and the moth Clanis bilineata 95.8% compared to casein. Protein digestibility of fresh termites Macrotermes subhylanus was 90.5%, of the green form of grasshoppers Ruspolia differens 82.3% and of the brown form of grasshoppers Ruspolia differens 85.7%.
The amino acid composition of insects ranges from approximately 40% – 95% of all nitrogenous substances.
Mostly, the fat content of edible insects is between 10% – 50%. Reports and analyzed results have shown that many edible insects are rich in fat; witchetty grubs have nearly 40% of fat (a composition similar to olive oil). The fat content of insects depends on many factors such as species, reproductive stages, season, age (life stage), or sex, habitat and diet.
For example, the fat content is higher in the larva and pupa stages; at the adult stage, the fat content is relatively lower. Female insects contain more fat than male insects. The content of essential fatty acids is higher as compared with animal fats.
Similarly, the fatty acid composition of related species is different, as there are many factors playing a role, too. Largely it is influenced by the host plant on which they feed. For insects that feed on a single food plant, the values are probably typical for all members of the species, in contrast, the fatty acid content of generalist feeders such as the house cricket, A. domesticus, is likely to vary widely depending on the diet being fed.
Lipids are vital in the structural and biological functioning of human cells and help in the transport of nutritionally essential fat-soluble vitamins. Especially those of the omega-3 long chain polyunsaturated fatty acids (LC-PUFA) have played an important role in human evolution, providing essential elements to build cerebral tissues.
Edible insects contain a good quality fatty acid especially long chain omega-3 fatty acids such as alpha-linoleic acid, eicosapentaenoic acid. The reason for insects containing long-chain PUFAs and different fatty acid compositions is linked with the diet and enzymatic activity in the insects.
One of the most important PUFA is DHA, which has been considered important for brain and eye development and also good cardiovascular health, and populations, which consume 0.5–0.7 g/day DHA have a lower incidence of heart disease. A few insect species are likely to be able to modify endogenously produced or dietary PUFAs to form the precursors to PGs (mammal prostaglandins) and related biologically active compounds.
Carbohydrates in insects are formed mainly by chitin. The carbohydrate content of edible insects ranged from 6.7% in sting bug to 16% in cicada. Research also showed that considerable amounts of polysaccharides might improve immune function of human body. Chitin is a macromolecular compound that has a high nutritional and health value.
As a form of low-calorie food, chitin also has a medicinal value. In most cases, the hard cover polysaccharide chitin of insects accounts for 5% – 20% of the dry weight. Chitin exists rarely in a pure form in nature but instead is usually in a complex matrix with other compounds (proteins, lipids and insignificant amounts of minerals).
Insects with ‘‘harder’’ cuticles do not seem to contain significantly more chitin than softer bodied insects but rather their ADF fraction seems to contain a much higher proportion of amino acids than softer bodied insects.
Although chitin presents problems of digestibility and assimilability in monogastric animals, it and its derivatives, particularly chitosan, possess properties that are of increasing interest in medicine, industry and agriculture. If the time should come when protein concentrates from insects are acceptable and produced on a large scale, the chitin byproduct could be of a significant value.
A significant contribution of chitin can be presented for example by significantly reducing serum cholesterol, acting as a hemostatic agent for tissue repair, enhancing burn and wound healing, acting as an anticoagulant,
protecting against certain pathogens in the blood and skin, serving as a non-allergenic drug carrier, providing a high tensile strength biodegradable plastic for numerous consumer goods, enhancing pollutant removal from waste-water effluent, improving washability and antistatic nature of textiles, inhibiting growth of pathogenic soil fungi and nematodes and boosting wheat, barley, oat, and pea yields by as much as 20%.
Insects are rich sources of minerals such as iron, zinc, copper, magnesium, and selenium. Analysis of mineral elements showed that edible insects are particularly rich in nutritious elements such as potassium and sodium (e.g. cricket nymph), calcium (e.g. cricket adult), copper (e.g. mealworm adult), iron (e.g. axayacatl – a mixture of several species of aquatic Hemiptera, giant mealworm), zinc (e.g. cricket nymph), manganese (e.g. cricket adult) and phosphorus (e.g. cricket adult).
The mineral composition in general probably largely reflects the food sources of insects, both those which are present in the gastrointestinal tract and those which are incorporated into the insect’s body as a result of the food it consumed.
For example, the calcium content of wax worms, house crickets, mealworms and silkworms can all be increased 5 to 20-fold when fed a high calcium diet. This increase in calcium appears to be solely due to the residual food in the gastrointestinal tract with little of the calcium being incorporated into the insect’s body.
All insects contain high levels of phosphorus, which results in a calcium: phosphorus ratio of less than one. For most monogastric animals, phosphorus from animal sources is virtually 100% available, while plant-based phytate phosphorus is approximately 30% available.
Insects could provide significant proportions of daily recommendations of minerals and, in particular, be excellent sources of bioavailable iron in the diets depending on the insect species.
Studies dealing with the vitamin content in insects are insufficient, yet it is known that edible insects contain mainly carotene and vitamins B1, B2, B6, D, E, K and C. As far as the A vitamin (retinol) is concerned, the data differ not only in dependence on the species, but also on the origin of analyzed insects, methods used and ways of preparation.
Commercially raised insects appear to contain little or no beta-carotene, most wild-caught insects contain a variety of carotenoids (astaxanthin, alpha-carotene, beta-carotene, lutein, lycopene, teaxanthin and others), which they accumulate from their food. Most species of vertebrates can convert some of these carotenoids to retinol, so insects containing high levels of carotenoids may be a significant source of vitamin A for insectivorous vertebrates.
Insects appear to be a good source of most B-vitamins, but a number of insects appear to contain low levels of thiamin. These low levels are likely an effect of heat processing, although the low levels seen for house crickets and superworms are for raw, whole insects.
The larvae of the mealworm have been mentioned as a promising option for mass rearing in Western countries because the species is endemic in temperate climates and easy to farm on a large scale, it has a short life cycle, and farming expertise is already available, particularly in the pet food industry.
In a study, insects were fasted for 24 hours to void their intestinal tract. The following conclusions were made (on a dry weight basis except for moisture and energy):
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