Determination of Moisture and Protein Content in Living Mealworm Larvae (Tenebrio molitor L.) Using Near-Infrared Reflectance Spectroscopy (NIRS)

Abstract

Yellow mealworm larvae (Tenebrio molitor L.) are a sustainable source of protein for food and feed. This study represents a new approach in analyzing changes in the nutritional composition of mealworm larvae using near-infrared reflectance spectroscopy (NIRS) combined with multivariate analysis. The moisture and protein content of living larvae were scanned with a near-infrared spectrometer using wavelengths from 1100 to 2100 nm. Different feeding groups with varying moisture sources and amount and the difference between low (50%) and high (75%) humidity were tested, and the influence on larval moisture and protein content was measured. A calibration was developed, with modified partial least squares as the regression method. The NIR spectra were influenced by the moisture and protein content of the larvae, because the absorbance values of the larval groups differed greatly. The coefficient of the determination of calibration (R2c) and prediction (R2p) were over 0.98 for moisture and over 0.94 for protein content. The moisture source and content also had a significant influence on the weight gain of the larvae. Consequently, significant differences in protein content could be determined, depending on the water supply available. With respect to wet weight, the larvae moisture content varied from 60 to 74% and protein content from 16 to 24%. This investigation revealed that with non-invasive NIRS online monitoring, the composition of insects can be continuously recorded and evaluated so that specific feeding can be carried out in the course of larval development and composition.

Influence of Dietary Protein Content on the Nutritional Composition of Mealworm Larvae (Tenebrio molitor L.)

“…However, the moisture content, too, of the larvae can have an effect on the nutrient composition of the larvae, since changes in moisture may also cause the other nutrients (e.g., protein and fat) to vary in content. The moisture content of Tenebrio molitor larvae presented here is comparable to other studies [ 12 , 41 , 76 ]. Several factors (e.g., water source, diet, and relative humidity) can influence the moisture content of mealworm larvae [ 12 , 76 , 77 ].…”

“…The moisture content of Tenebrio molitor larvae presented here is comparable to other studies [ 12 , 41 , 76 ]. Several factors (e.g., water source, diet, and relative humidity) can influence the moisture content of mealworm larvae [ 12 , 76 , 77 ]. Tenebrio molitor larvae showed a significant linear ( p < 0.001) and quadratic ( p <0.001) higher moisture content in the groups PPF80 and PPF60, which were fed with a high proportion of pea protein flour, because this substrate was highly hygroscopic.…”

Near-Infrared Reflectance Spectroscopy for Quantitative Analysis of Fat and Fatty Acid Content in Living Tenebrio molitor Larvae to Detect the Influence of Substrate on Larval Composition

“…A number of environmental factors (temperature, humidity, light, etc.) have been shown to affect the development, growth, and nutritional composition of insects [ 22 , 34 , 36 ].…”

“…In addition, the fat or fatty acid content of meat [ 19 ], cereals and their products [ 20 ], or cocoa beans [ 21 ] can already be predicted by NIRS. As we have demonstrated in our previous study [ 22 ], NIRS can be used to predict the moisture and protein content of mealworm larvae. Thus, the present work focused on determining the fat content and fatty acid composition of living Tenebrio molitor larvae using NIRS due to the deficiency of known applications for such measurements.…”

Development of semi-artificial feed in the larva stage of the black soldier fly Hermetia illucens (Diptera: Stratiomyidae)

“…Insects have high water, protein, and fat content. Fat content has the opposite relationship with water content; the higher the water content, the lower the fat content (Kroncke and Rainer 2022).…”