2.1. Reagents and samples
Standards of thiamine and riboflavin, as well as enzymes
(diastase, alpha-amylase, beta-amylase, acid phosphatase, papain
and pepsin) and other common enzymes were purchased from
Sigma (St. Louis, USA). HPLC grade solvents were purchased from
Symta (Madrid, Spain). Commercial complex cereal products, consisting
of breakfast cereal food (containing rice, oat, whole wheat,
wheat flour and wheat bran) with enrichment levels of 2e2.7 mg/
100 g of vitamins B1 and B2, were purchased from local markets.