Do cooking techniques influence copper bioaccesibility in foods after in vitro digestion/fermentation in adults and children?

Cu is essential for the growth and organism health. Classically, its available fraction has been studied by in vitro digestion studies as a measure of bioaccessibility of Cu (Cu-BA). In this work we applied a novel in vitro digestion/fermentation method to multiple foods subjected to different home cooking techniques (raw form vs. frying, roasting, toasting, boiling and grilling) by metabolization with faecal inoculate from healthy adults (HE-AD), and healthy children (HE-CH) and sick children (children with gluten related disorders, GRD-CH; children with obesity, OB-CH; and children with allergy/intolerance to cow's milk proteins, AICM-CH). In raw and cooked foods the bioaccessibility of Cu in the small intestine (Cu-BASI) was higher vs. that in the Cu bioaccessibility in the large intestine (Cu-BALI) (30.8 ± 15.4 and 28.2 ± 14.7 vs. 18.4 ± 21.2 and 22.8 ± 22.1 %, respectively; p < 0.001). Total Cu-BA in cooked foods (51.0 ± 24.4 %) was higher than that in raw foods (49.0 ± 25.1 %). In cereals, total Cu-BA was higher in the raw form, as well as in whole grains and those with gluten (p < 0.05). In vegetables, the most drastic cooking techniques (roasting and frying) show higher values of total Cu-BA compared to raw form and boiling. The Cu-BALI in HE-CH (37.7 ± 23.7 %) is higher than that determined in HE-AD (14.1 ± 18.5 %) and sick children (GRD-CH: 14.6 ± 19.8; OB-CH: 15.5 ± 17.8; and AICM-CH: 26.9 ± 19.3 %; p < 0.001). In conclusion, cooking techniques influence Cu-BA depending on the food group. Total Cu-BA, as well as that determined in the large and small intestine varied according to the category, group and specific foods, which is related to their different composition and species of the element. In healthy children, total Cu-BALI is higher than in adults and celiac, obese and allergic children probably due to growth requirements and specific microbiota.