**5.1 Waste valorisation: insect-based bioconversion of agri-food waste and by-products into food**

Insects can be farmed for food or feed. Currently, mealworms (*Tenebrio molitor*) and crickets (*Acheta domesticus*) are the main species farmed for human consumption. The nutritional composition of each insect varies due to factors such as rearing conditions, diet, and age. However, values typically sit between 15% and 25% protein, 4% and 13% fat and 2% and 4% fibre (made up mostly of chitin) (per 100 g edible portion) [79]. Both species also provide a source several vitamins and minerals, including iron, zinc, vitamin B2 and vitamin B12 [80]. While commercial mealworm and cricket farming remains mostly reliant on mixed grain and soy-based feeds [81, 82], several agri-food waste and by-products have been explored as sole or supplementary feeding substrates substrates [76] (**Figure 4**). This includes:


Despite clear potential for agri-food waste and by-products as feed for mealworms and crickets, several challenges remain. Firstly, while recent findings suggest that insects can be reared on organic waste streams, growth performance and survival rates vary. Mixed feeds (composed of more than one substrate) are therefore recommended to better meet physical and nutritional diet requirements [76, 83]. Local and year-round substrate availability should also be considered, alongside regulatory restrictions. For example, in regions such as Europe and Australia, insects are regarded as farmed animals and therefore subject to animal feed regulation. Potential feed sources such as catering waste are consequently prohibited from use [76, 84].

#### **5.2 Incorporation of insects in extruded foods**

Edible insects such as mealworms and crickets can be used in food to improve nutritional composition, substitute conventional protein sources, or contribute sensory attributes (e.g., flavour and texture). To prepare these species for human consumption, they typically undergo a series of processing steps including (1) inactivation/killing (generally by freezing, blanching, or steaming); (2) washing; (3) blanching; and (4) drying (generally by oven-drying or freeze-drying). Following drying, mealworms and crickets can be used whole, ground, or further processed to extract protein, lipids, and chitin.

Poor consumer acceptance remains a key barrier to the commercialisation of insect foods in Western food cultures, mainly driven by a lack of familiarity with insects in the context of food. However, research suggests that the use of non-recognisable insect ingredients (e.g. powder, flour, insect protein concentrate, texturized insect protein) could help to change perceptions [85]. Familiar foods such as bread, baked goods, pasta, and corn chips incorporating insect powder and flour are wellestablished among commercially available insect-based foods (e.g., Grillon Le Pain 'Crickbread', Chirps 'Chocolate Chirp Cookie mix', Sens 'Cricket Protein Pasta', Circle Harvest 'Cricket Corn Chips'). However, extrusion processing presents an emerging pathway for the expansion of non-recognisable insect ingredients in several product categories, including breakfast cereals, snack products and meat analogues. Several studies have already investigated applications for insect-ingredients in extruded food products, including protein enrichment in expanded snacks as well as soy substitution in meat analogues. Expanded snacks demonstrated acceptable sensory properties at 6– 15% substitution [86–89] while 30–40% substitution was shown to provide meat-like properties and enhance flavour in meat analogues [90, 91]. Due to poor expansion properties, the high lipid and protein content of cricket and mealworm powders

remains a key barrier to further enrichment of expanded snacks [86, 87]. However, some early products are already commercially available (e.g., Actually Foods 'Food puffs').

While the potential for insect-based extruded food products is promising, the nascent nature of the edible insect industry presents some challenges. Crucially, regulatory issues (related to approval of novel foods and a lack of clear industry standards) remain a key constraint to the farming and use of insects in food. Further research is also required to ensure safe farming, processing, storage and transport of insects and insect-based foods, as well as for management of allergenic risks (e.g., cross-reactive allergies and potential novel insect allergens) [92].
