Potential of insect proteins for food and feed : Effect of endogenous enzymes and iron-phenolic complexation

Abstract

Insects have been identified as excellent alternative source of proteins due to their high protein content. The acceptance of insects increases when used as ingredient in an invisible manner and hence grinding is necessary. Off-colour formation occurs upon grinding larvae, which can hamper their potential use as ingredient for food and feed. The aim of this thesis was to investigate potential of insect larvae as protein source, the mechanisms responsible for the browning or blackening of larvae during grinding, and its impact on protein functionality. This was investigated for the larvae of three species: Tenebrio molitor, Alphitobius diaperinus and Hermetia illucens. The specific Kp factor of 4.76±0.09 was determined for the three species to determine protein content based on nitrogen, and 5.60±0.39 after protein extraction and purification. Thus, the general Kp factor of 6.25, used until now, overestimated the protein content in insects. Off-colour formation upon grinding was caused by both enzymatic and non-enzymatic browning. Phenoloxidase was found to be mainly responsible for browning in T. molitor and likely in A. diaperinus, whereas iron-phenolic complexation likely contributed to the black colour in H. illucens. A model system of L-DOPA and iron was used to elucidate the structures of the iron-L-DOPA complexes by mass spectrometry. Enzymatic browning did not influence the solubility of the proteins of all three species. Upon in-vitro hydrolysis by pepsin and trypsin, soluble proteins from H. illucens were more digestible compared to those of T. molitor and A. diaperinus. Phenoloxidase activity during processing negatively affected in-vitro pepsin hydrolysis. Besides phenoloxidase activity, also endogenous proteases remained active at pH 8 in extracts of insect larvae. Summarizing, endogenous enzyme activities and iron complexation should be taken into account for future application, as well as the specific Kp factor to prevent overestimation of the protein content of insects. v 7 CONTENTS Chapter 1 General introduction Chapter 2 Nitrogen-to-protein conversion factors for three edible insects: Tenebrio molitor, Alphitobius diaperinus and Hermetia illucens Chapter 3 Involvement of phenoloxidase in browning during grinding of Tenebrio molitor larvae Chapter 4 Iron-polyphenol complexes cause blackening upon grinding Hermetia illucens (black soldier fly) larvae Chapter 5 Effect of endogenous phenoloxidase on protein solubility and digestibility after processing of Tenebrio molitor, Alphitobius diaperinus and Hermetia illucens

Nutritional, Techno-Functional and Structural Properties of Black Soldier Fly (Hermetia illucens) Larvae Flours and Protein Concentrates

“…Protein solubility around the apparent pI, on the other hand, was the lowest since there was slight repulsion. These results are in agreement with previously reported data for BSFL [ 49 ]. Typically, proteins (e.g., from milk, soy, egg) used as ingredients in the food industry have an isoelectric point in the pH range 4–6 [ 45 ].…”

Insects as Food - The Opinion of Latvian Consumers

“…Insects also have rich content of mono-and polyunsaturated fatty acids; they are rich in trace elements such as copper, iron, magnesium, manganese, phosphorus, selenium and zinc, as well as vitamins like riboflavin, pantothenic acid, biotin, and folic acid in some cases [3,4]. Insects are nutritionally interesting material, and they may be included in a common diet of consumers in the EU countries in the near future [4,5]. The high environmental impact connected with meat production and the increase in demand until 2050 require dietary changes.…”

“…The high environmental impact connected with meat production and the increase in demand until 2050 require dietary changes. Insect-based meat substitutes are potentially more sustainable [5][6][7][8][9]. Of course, this global topicality will also affect Latvia, but it is important to get to know the taste of the Latvian people in order to find the best approach to the integration of the recent trends into eating habits.…”