Lactic Acid and Thermal Treatments Trigger the Hydrolysis of Myo-Inositol Hexakisphosphate and Modify the Abundance of Lower Myo-Inositol Phosphates in Barley (Hordeum vulgare L.)

Barley is an important source of dietary minerals, but it also contains myo-inositol hexakisphosphate (InsP(6)) that lowers their absorption. This study evaluated the effects of increasing concentrations (0.5, 1, and 5%, vol/vol) of lactic acid (LA), without or with an additional thermal treatment at 55°C (LA-H), on InsP(6) hydrolysis, formation of lower phosphorylated myo-inositol phosphates, and changes in chemical composition of barley grain. Increasing LA concentrations and thermal treatment linearly reduced (P<0.001) InsP(6)-phosphate (InsP(6)-P) by 0.5 to 1 g compared to the native barley. In particular, treating barley with 5% LA-H was the most efficient treatment to reduce the concentrations of InsP(6)-P, and stimulate the formation of lower phosphorylated myo-inositol phosphates such as myo-inositol tetraphosphate (InsP(4)) and myo-inositol pentaphosphates (InsP(5)). Also, LA and thermal treatment changed the abundance of InsP(4) and InsP(5) isomers with Ins(1,2,5,6)P(4) and Ins(1,2,3,4,5)P(5) as the dominating isomers with 5% LA, 1% LA-H and 5% LA-H treatment of barley, resembling to profiles found when microbial 6-phytase is applied. Treating barley with LA at room temperature (22°C) increased the concentration of resistant starch and dietary fiber but lowered those of total starch and crude ash. Interestingly, total phosphorus (P) was only reduced (P<0.05) in barley treated with LA-H but not after processing of barley with LA at room temperature. In conclusion, LA and LA-H treatment may be effective processing techniques to reduce InsP(6) in cereals used in animal feeding with the highest degradation of InsP(6) at 5% LA-H. Further in vivo studies are warranted to determine the actual intestinal P availability and to assess the impact of changes in nutrient composition of LA treated barley on animal performance.