The effect of citric acid, heat, and high-pressure on the morphology and physiology of Bacillus spores : simulating high-pressure processing of complementary foods

Abstract

To ensure the safety and quality of infant complementary foods (CFs), a combination of citric acid (CA), heat (H), and high-pressure (HP) treatments can be used. The impact of these treatments on the physiological state and morphology of spores of Bacillus spp. was studied. B. amyloliquefaciens TMW 2.479 Fad 82 spores were suspended in CA and subjected to H at 100 °C for 25 min, followed by HP at 600 MPa for 3 and 4 min at 9 °C. Spore germination rate for all the treatments was below 10 % and all the treatments except CA affected the spore's morphology. However, H treatment alone or combined with HP and CA disrupted the internal membrane (IM) and enhanced the damage to the B. amyloliquefaciens spores Cortex (Cx). Acidification of the B. amyloliquefaciens spores with CA led to the permeability of the spore's IM but with intact Cx. The combined treatments of CA, H, and HP significantly affected the integrity of the spore's intracellular structure. This study elucidates how the sequential application of CA, H, and HP can affect the morphology and physiology of Bacillus spores and improves the safety and quality of infant CFs. HIGHLIGHTS • H treatment induced the highest level of B. amyloliquefaciens spore germination. • HP with H and CA, damaged Bacillus spore without adequate germination. • Sequential treatment damaged the IM and Cx of B. amyloliquefaciens spore. • Extra HPP step for 3 min improves the safety and quality of infant CFs.