Abstract
Barley is an important source of dietary minerals, but it also contains myo-inositol hexakisphosphate (InsP6) 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 InsP6 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) InsP6-phosphate (InsP6-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 InsP6-P, and stimulate the formation of lower phosphorylated myo-inositol phosphates such as myo-inositol tetraphosphate (InsP4) and myo-inositol pentaphosphates (InsP5). Also, LA and thermal treatment changed the abundance of InsP4 and InsP5 isomers with Ins(1,2,5,6)P4 and Ins(1,2,3,4,5)P5 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 InsP6 in cereals used in animal feeding with the highest degradation of InsP6 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.
Highlights
Barley is an important cereal crop used for livestock feeding and human consumption
Myo-inositol hexakisphosphate concentration decreased in response to lactic acid (LA) treatment and, in particular, when barley was treated with LA and ovenheated at 55uC (Figure 1)
In the feeding of monogastric livestock species such as swine and poultry, processing techniques used to increase P availability of feeds are often restricted to microbial phytase supplementation [8,32]
Summary
Barley is an important cereal crop used for livestock feeding and human consumption It contains relatively large amounts of starch, protein, dietary fiber, and minerals which make this cereal a highly valuable ingredient of the diet [1]. It represents an important source of phosphorus (P), with total P content exceeding 4 g per kg dry matter (DM). Endogenous cereal phytases that catalyse the hydrolysis of InsP6 to inorganic P and lower myo-inositol phosphates (InsP), most importantly myo-inositol pentaphosphates (InsP5), myo-inositol tetraphosphates (InsP4), and myo-inositol triphosphates (InsP3) [6], during germination can be activated by luminal conditions (i.e., pH) in the gastrointestinal tract, rendering a certain amount of P available for the host [7]. Compared with other cereals such as rye and wheat, barley grain possesses lower endogenous phytase activity [2], emphasizing the necessity to treat barley grain to improve intestinal P availability
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