Enhancing Micronutrients Bioavailability through Fermentation of Plant-Based Foods: A Concise Review

Plant-based foods are rich sources of vitamins and essential micronutrients. For the proper functioning of the human body and their crucial role, trace minerals (iron, zinc, magnesium, manganese, etc.) are required in appropriate amounts. Cereals and pulses are the chief sources of these trace minerals. Despite these minerals, adequate consumption of plant foods cannot fulfill the human body’s total nutrient requirement. Plant foods also contain ample amounts of anti-nutritional factors such as phytate, tannins, phenols, oxalates, etc. These factors can compromise the bioavailability of several essential micronutrients in plant foods. However, literature reports show that fermentation and related processing methods can improve nutrient and mineral bioavailability of plant foods. In this review, studies related to fermentation methods that can be used to improve micronutrient bioavailability in plant foods are discussed.

Effect of Fermentation and Mango Mesocarp or Fluted Pumpkin Powders on the Chemical Composition and Potential Mineral Bioavailability of Sorghum-Based Complementary Foods

The effect of fermentation, mango mesocarp or fluted pumpkin leaf powders on the chemical properties and potential mineral bioavailability of sorghum-based complementary foods was investigated. Samples were formulated based on 16% protein to satisfy the nutrient requirement of preschool children to obtain non-fermented sorghum/mango mesocarp/crayfish (NFSMC), non-fermented sorghum/fluted pumpkin leaf/crayfish (NFSPC), fermented sorghum/ mango mesocarp/crayfish (FSMC) and fermented sorghum/ fluted pumpkin leaf /crayfish (FSPC). Some physico-chemical properties of the blends were analysed using standard procedures. Moisture (10.22–10.99%) and carbohydrate (78.73-79.89%). The protein (15.84-16.91%), fibre (0.07-0.08%) and ash (2.07-2.15%) were within the recommended limits. Fat contents ranged from 2.00-2.16% and energy values ranged from 401.40 to 402.10 kCal. Fermentation did not significantly (p ≥ 0.05) affect the proximate composition of the products. The mineral values for magnesium (53.25-61.60%), sodium (32.06-46.30%), potassium (20.80-44.66%), calcium (198.60-230.30%) and phosphorus (98.99-101.50%) with no significant (p ≥ 0.05) difference in most of the products. The iron and copper values ranged from 10.03-17.09% and 0.42-1.43% respectively. Mineral ratios for the products ranged from 0.74 – 2.19 for Na/K, 1.96 – 2.71 for Ca/P and 3.69 – 5.07 for Ca/Mg. The tannins content ranged from 20.23 to 51.51 mg/100 g, phytate (7.25-22.16 mg/100 g), oxalate (5.50 to 14.37 mg.100 g), pH (6.20 to 7.80) and beta-carotene ranged from 724.50 - 1215.40 µg/100 g with significant (p<0.05) difference between the blends. The molar ratios of the blends, except NFSMC, indicated good potential for mineral bioavailability.

Phytic Acid in Brown Rice Can Be Reduced by Increasing Soaking Temperature

Phytic acid (PA) is a storage form of phosphorus in seeds. Phytase enzyme is activated at germination and hydrolyses PA into myo-inositol and inorganic phosphate. PA inhibits the absorption of minerals in the human intestine by chelation. Its degradation, therefore, is a key factor to improve mineral bioavailability in rice. Germinated brown rice (GBR) is favoured because it improves the availability of nutrients, and thus have a positive effect on health. In this study, we show the effects of soaking temperature on phytase activity and PA content in GBR. Rice phytase showed thermostability and its activity peaked at 50 °C. After 36 h of soaking, phytase activity was significantly increased at 50 °C and PA content was significantly decreased, compared to that at 30 °C. Zinc (Zn) analysis revealed that there was no significant difference in Zn content among different temperature treatments. Calculated total daily absorbed Zn (TAZ) was significantly higher in GBR compared with non-soaked seeds. Moreover, brown rice grains germinated at 50 °C showed a higher TAZ value than that at 30 °C. Seed germination and seed water soaking at high temperatures reduce PA content in brown rice showing a potentially effective way to improve mineral bioavailability in brown rice.

Amino Acid Profile, Mineral Bioavailability, and Sensory Properties of Biscuits Produced from Composite Blends of Wheat, Coconut and Defatted Fluted Pumpkin Seed Flour

The objective of this work was to produce biscuits from composite flour of wheat, coconut, and defatted fluted pumpkin seed and to evaluate the mineral bioavailability, amino acid profile and sensory properties of the composite biscuits. Wheat/coconut/defatted fluted pumpkin seed flours were blended in the ratio; 100/0/0, 80/10/10, 70/20/10, 60/30/10, 50/40/10, 40/50/10 and labelled as sample A, B, C, D, E and F respectively. Biscuits were baked with these composite flours using the creaming method. Lysine content ranged from 3.35-5.07g/100g, with sample F given significantly higher value followed by samples E (4.70g.100g) and D (4.33g/100g). All the essential amino acids increased significantly with increased substitution of coconut and fluted pumpkin seed flour, except phenyl-lanine and cysteine that decreased from 4.98 – 3.90 and 1.22 – 0.69g/100g respectively in sample A to E. Sample E gave higher total Ca, Fe, K and Zn of 26.89, 17.92, 86.02 and 2.82mg/100g respectively. Percentage bioavailability of Ca, Fe, Na, K and Zn were significantly higher in sample F with values of 59.67, 51.35, 58.22, 59.67 and 47.74% respectively. Sample E recorded the highest overall acceptability score of 6.38. This score was however not significantly different from scores obtained for samples A, B, C and D. Production of composite biscuits with 50/40/10% wheat/coconut/defatted fluted pumpkin seed flour is highly recommended.