Transglutaminase-crosslinked lesser mealworm protein isolate: A new milk fat substitute for high-quality probiotic set yogurts

Abstract

Innovative non-fat probiotic set-style yogurts (NF-PSSYs) incorporated with lesser mealworm protein isolate (LMPI) crosslinked by microbial transglutaminase (MTGase) were optimized. The utilization of 4.65% w/w MTGase-crosslinked LMPI and 10.1 Log CFU/mL of Lactobacillus acidophilus La-5® resulted in maximum lightness, firmness, apparent viscosity, and probiotic survivability, and minimum syneresis with a desired acidity in NF-PSSYs. The fluorescence microscopy images and laser diffraction particle size analyses revealed small protein clusters with fine serum pores in the optimal yogurt gel. The sensory properties of optimal NF-PSSYs deteriorated slower than the control ones during refrigerated storage. A significantly lower loss rate in the DPPH inhibition activity, ferric-reducing power, and riboflavin content was found in optimal NF-PSSYs than in control yogurts. The attenuated total reflectance-Fourier transform infrared (ATR-FTIR) efficiently explored structure-activity relationships related to organoleptic and antioxidant properties. The in vitro simulated gastrointestinal digestion showed that the optimal yogurt had the highest digestive product content with fractions of molecular weight <15 kDa and proteolysis rate by pepsin and trypsin for 50 and 30 min, respectively. MTGase-crosslinked LMPI would be a promising fat replacer for manufacturing high-quality NF-PSSYs.