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 degrees 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 degrees 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.