As a very rich kind of organisms on the earth, insects have a long history of eating insects in China and even the world. However, due to the problems of customs, culture and safety, the development of insects as food raw materials is relatively slow. As the global population grows, the food industry is looking for alternative forms of animal protein through various avenues. Insects are nutritious, tasty, and viable alternative food options for animals. Their potential is growing due to the current trend towards a high place of emphasis on cultural diversity and the global awareness of the urgent need to address the environmental impacts of contemporary agricultural systems. In 2021, the European Commission issued Regulation (EU) 2021/8820 to approve dried mealworm larvae to be placed on the market as a new resource food, which is the first approved insect food new resource food in the European Union.
Mealworm is rich in nutrition, low feeding cost, protein content of 49%~55%, amino acid species and proportion are close to the standards recommended by the WHO, and the content of unsaturated fatty acids is high, rich in chitosan, is an insect resource with great development potential. Compared to the nutrients of other common edible insects (such as crickets), mealworms are not only high in protein, but also high in fat (~30%), which can provide the essential fatty acids that the body needs. In addition, the protein and fat content of different insect states are different, and mealworms with different insect states can be selected according to the needs of deep processing. The difficulty of raising mealworms is low, the reproduction is fast, the breeding cost is low, and the domestic enterprises that carry out large-scale modern breeding of mealworms are gradually emerging. Compared with the research and development of insect food in foreign countries, the development of insect food in China is still relatively lagging behind due to regulations. But with the rise of animal protein alternatives, mealworms are bound to gain more attention from the food industry as a high-protein alternative.
This article will comprehensively describe the processing methods of mealworms and their impact on nutritional value, and summarize the different application scenarios of mealworms.
Nutritional value of mealworms
Mealworms are killed by freezing, blanching, etc., after being removed during processing, and usually need to be further dried and preserved. Mealworms have high nutritional value and are easy to cause microbial growth if not dried. The drying methods include hot air drying, freeze drying, microwave drying and vacuum drying. Studies have shown that the way mealworms are dried has an impact on their color and nutritional value.
Different application scenarios of mealworms
1. Simulate meat products
Producing insect protein has less environmental burden, feed costs and greenhouse gas generation than animal protein, so developing insect protein as a meat substitute for the future is one of the solutions to future population growth and environmental degradation. The use of mealworm meal, defatted mealworm meal or mealworm protein to replace some animal meat in meat products can avoid consumer consumption decisions caused by aversion to insect morphology.
Orkusz compared the nutritional value of a variety of meat products and insects and found that insects and meat products are comparable in protein, essential amino acids and essential fatty acids, and can provide the nutrients needed by the human body, in addition to vitamin C and dietary fiber. Cho and Ryul added mealworm powder to a plant-based protein simulated meat product, with a base ingredient of 65% defatted soybean flour, 25% soy protein isolate, and 10% cornstarch, and mealworms were added with 15% and 30% of the base ingredient and extruded by a twin screw to obtain the simulated meat. Mealworm meal increases protein solubility and digestibility as well as antioxidant activity, but decreases the textural properties of mimic meat, which may be due to mealworm meal weakening molecular interactions within the soy protein network, similar to the effect of mealworm meal added to the gluten network.
Compared to freeze-dried mealworm raw materials, dried and microwave-dried mealworm raw materials have a better aroma, which may be due to the Maillard reaction that occurs during the drying process due to the increase in temperature.
2. Application of mealworm oil
As an insect rich in oil, mealworms can not only provide rich protein but also be used to extract mealworm oil, usually by organic solvent extraction. The fatty acid composition of its oils and fats is shown in Table 3, which contains a high content of unsaturated fatty acids, among which oleic acid and linoleic acid are the most abundant.
The vitamin E content of mealworm oil measured by Son et al. was 144.3 mg/1000g oil, which was higher than that of most animal-derived oils and slightly lower than that of vegetable oils. Jeon et al. studied the effect of frying at 200°C for 5~l5 min on mealworm oil, and found that frying would deepen the color of the oil and increase the content of oleic acid and tocopherol, and the fried mealworm oil showed better oil oxidation stability, which may be due to the certain antioxidant activity of the Maillard reaction product produced during the frying process.
3. Application of mealworm protein
The solubility, emulsification, foaming and functional properties of mealworm protein and its hydrolysate have been determined.
Yoo et al. prepared hydrolysates of insect proteins such as mealworm protein by hydrolysis of flavor enzyme, alkaline protease or a mixture of both, and found that the solubility was significantly increased and the foaming property was reduced after hydrolysis by several enzymatic hydrolysis methods. Flavor enzyme treatment significantly improved the emulsifying activity and stability of mealworm protein. Angiotensin-converting enzyme was significantly inhibited by alkaline protease hydrolysis, and treatment with enzyme mixture showed effective inhibition of α-glucosidase activity. The functional properties of mealworm protein isolate are comparable to existing commercially available plant proteins, and have the potential to be applied to food systems. Studies have been conducted on the preparation of emulsions using mealworm protein and the design of bioactive substance delivery systems such as curcumin. Grossmann et al. hydrolyzed mealworms and reacted with xylose at 98°C for 30 min, and the Maillard reaction enhanced its bitterness and umami intensity, indicating that mealworm protein hydrolysates could be used as raw materials for the development of new flavor substances.