Mechanisms of flavonoid inhibition of Maillard reaction product formation in relation to whole grains processing.

Whole grains (WG) are beneficial to health but have reduced sensory quality, partly attributable to inhibition of Maillard reaction products (MRP) by WG phenolics. The study investigated how major flavonoid classes in cereals affect Maillard reaction pathways. Flavonoids were reacted with xylose-lysine aqueous system at 160 °C/12 min. Additionally, breads were made with catechin, and wheat and sorghum bran fortification. Low Mw MRP were profiled using UPLC-MS/MS, while melanoidins were characterized using fluorescence spectroscopy and HPSEC-MALS. The flavonoids significantly (p < 0.05) reduced both melanoidin content (by 33-86%) and Mw (3.5-15 kDa vs 20 kDa control), leading to lighter bread crust. Flavonoids inhibited MRP via direct condensation with early-stage amines and carbonyls into stable adducts, and reduction of late-stage polymerization reactions, increasing accumulation of cyclic N-containing intermediates. Inhibitory trend was flavones>flavanones>flavanols. C-Ring π-bond dramatically enhance flavonoid MRP inhibition; thus flavone-rich cereal grains are likely to strongly impact MRP-dependent sensory attributes of WG products.

Polyphenol recovery from sorghum bran waste by microwave assisted extraction: Structural transformations as affected by grain phenolic profile.

Sorghum milling waste stream (bran), contains diverse phenolic compounds with bioactive properties. The study determined the potential of microwave assisted extraction (MAE) to recover the bran phenolic compounds. Red, white, and lemon-yellow pericarp sorghum brans were subjected to MAE and phenolic yield and structural transformation vs conventional extraction (control) assessed by UPLC-MS/MS, Folin-Ciocalteu and Trolox equivalent antioxidant capacity methods. Phenols yield increased from 3.7-20.3 to 12.6-75.5 mg/g, while antioxidants capacity increased average 3.3X in MAE extracts vs controls. Hydroxycinnamic acids increased most dramatically (3.0-32X) in MAE extracts (0.08-2.64 to 2.57-8.01 mg/g), largely driven by release of cell-wall derived feruloyl- and coumaroyl-arabinose. MAE hydrolyzed flavonoid glycosides into aglycones, and depolymerized condensed flavonoid heteropolymers into flavanones, flavanols and (deoxy)anthocyanidins. Thus, MAE dramatically enhances yield of valuable phenolics from sorghum bran waste, but also alters the phenolic profile in ways that may influence their chemical and biological properties.

Effect of cereal bran phenolic profile on Maillard reaction products formation during hydrothermal treatment.

Maillard reaction products (MRP) contribute to sensory quality of various foods. Whole grains (WG) are rich in phenols which may influence Maillard reaction pathways during thermal processing and impact WG product sensory attributes. This study investigated how WG phenolic profile affects MRP formation. Amylase-hydrolyzed wheat (white and red) and sorghum (white, red, tannin) brans were hydrothermally processed at 150 °C/6 min, and characterized for MRP using colorimetry, fluorescence spectroscopy, HPLC-MS/MS, and HS-SPME/GC-MS. Bran phenolic structure, and to a lesser extent content, had larger influence on MRP formation than protein/amino acid profile. Polymeric tannins (both in situ and when added to wheat brans) strongly inhibited volatile and non-volatile MRP intermediates and melanoidin formation, likely via their carbocation depolymerization intermediates trapping furans. Principle component analysis demonstrated clear segregation of volatiles formation based on bran phenolic profile. Phenolic composition should be considered in WG product formulation and processing to achieve desired MRP formation.

In vitro protein digestibility of finger millet complementary porridge as affected by compositing precooked cowpea with improved malted finger millet.

Protein-energy malnutrition is one of the leading causes of death for children under-five in developing countries and Kenya is no exception. These children rely on starchy weaning foods such as finger millet (Eleusine coracana), which have poor protein digestibility. Cowpea (Vigna unguiculata), a locally available nutritious legume, could be an excellent complement to lysine-deficient millet diets. The present study thus aimed at innovatively improving protein digestibility of a baby weaning food, by evaluating the effect of malting on improved finger millet genotypes (U15, P224, KNE741, KNE629 and Snapping green) to enable selection of the best varieties with superior nutritional credential post process. Blending of selected finger millet with precooked cowpea flour followed the WHO recommended level at 10.32%, 21.26%, and 32.75% with 0% as control. Extractable phenols, condensed tannins, phytic acid, protein content, and protein digestibility were determined using recommended methods. Extractable phenol, condensed tannin, and phytate notably decreased by 44%, 47%, and 29% respectively after malting. Additionally, compositing with precooked cowpea increased protein content and protein digestibility in flour by about 6-39%. Cooking resulted in a 10% increase in protein digestibility in the complementary porridge. Malting of finger millet and compositing it with precooked cowpea has the potential to address PEM as it results in reduced anti-nutritional content with a concomitant improvement in protein digestibility of the baby weaning food.