The Effect of Grinding Time on Moisture Sorption, Particle Size Distribution, and Phenolic Bioaccessibility of Carob Powder

Abstract Carob pods were ground for 30–180 s in a vibratory grinder. Particle size, colour, moisture sorption properties, antioxidant properties, and phenolic contents were examined. A static three-stage in vitro (oral, gastric, and intestinal) digestion process was performed to determine the fate of phenolic compounds and the antioxidant properties of the carob powder samples.The median values (D50) of particle size decreased after 60 s of grinding (87.9 μm), then increased to 135.1 μm. Lightness showed a negative correlation with D50 and aw, while redness and yellowness values decreased with the reduction of particle size and water activity. The smaller the particle size, the higher the equilibrium moisture content of carob powder. Phenolic acids (vanillic, ferulic, cinnamic) and flavonoids (luteolin, naringenin, apigenin) were found in all samples of carob powder. The grinding time influenced their content with maximum values in carob pods ground for 180 s. Similar observations were made when assessing antioxidant capacity. The in vitro digestion process improved the bioaccessibility of catechin content in all samples. However, the bioaccessibility of phenolic compounds, total phenolic and flavonoid content decreased with the increase in grinding time. Our findings revealed that the grinding of carob pods for 180 s improved the extractability of phenolics, however, their bioaccessibility was reduced. It is sufficient to ground carob pod for 30 s, which ensures good availability of nutraceuticals and lower energy cost for grinding.