Screening for anti-nutritional compounds in complementary foods and food aid products for infants and young children

Abstract

A range of compounds with negative nutritional impact - 'anti-nutrients' - are found in most plant foods. The contents of anti-nutrients in processed foods depend on the ingredients and processing. Anti-nutrients in complementary foods for children can have a negative impact on nutritional status. The aim of this study was to screen complementary foods from developing countries for the anti-nutritional compounds, phytate, polyphenols, inhibitors of trypsin and chymotrypsin, and lectins. Commercial products based on whole grain cereals were included as a 'worst-case' scenario for anti-nutrient exposure in Europe. Contents of minerals (iron, zinc and calcium), in which absorption or utilisation is affected by anti-nutrients, were analysed. Thirty-six products representing foods used in food aid programmes, local blended foods, fortified instant porridges and 'baby foods' were analysed. The content of minerals indicated that the fortification of a number of products did not meet the declared levels of iron, zinc and calcium. The phytate content ranged from 68 to 1536 mg/100 g, confirming a persistent problem of high levels of phytate in processed cereal- and legume-based products. The phytate : Fe molar ratio exceeded the recommended level of <1.0 in 32 of the 36 products. The total polyphenols varied from 1.3 to 9.3 mg gentisic acid equivalents g(-1) . Screening low-molecular weight soluble polyphenols may be more relevant in complementary foods than total polyphenolic compounds. Trypsin and chymotrypsin inhibitors and lectins were found in residual amounts in most products, indicating efficient degradation by heat processing. However, young infants and malnourished children may have reduced pancreatic function, and upper limits for residual trypsin inhibitors are needed.

Figure 1

Phytate [inositol hexaphosphate (IP6)] contents and phytate : mineral molar ratios by product. Error bars indicate standard deviation between replicate samples of products. Product description is shown in Table 1. Products 4 and 32 were sampled in replicates with different premix compositions. Horizontal lines indicate recommended maximum molar ratios for optimal mineral bioavailability. Phytate : iron ratio =1; phytate : Zn ration =15 and phytate : Ca ratio = 0.17.

Figure 2

Anti‐nutrient by‐products by exposure from a daily portion. A daily portion is calculated as 200 kcal, except for products 18 and 19, which are supplements to be added to a porridge in a daily ration of 12 g (44 kcal) and products 23 and 32a, which are supplement to be used in a 20 g daily ration. Product description is shown in Table 1. Products 4 and 32 were sampled in replicates with different premix compositions. (A) Inositol hexaphosphate (IP6); (B) total polyphenols [tannins, Folin–Ciocalteu, standard: gentisic acid (2,5‐dihydroxybenzoic – DHB)]; and (C,D) chymotrypsin and trypsin inhibitors: IU g⁻¹ = inhibitor units (IU) per gram of samples. Lectin: concanavalin A reactive glycoprotein.

Figure 3

Example of low‐weight molecular separation of two samples, one peanut‐based lipid paste (product 25) and one maize‐ and soya‐based fortified blended food (product 3). Separation was conducted by the three‐column ionic separation technique, followed by simple fingerprint‐type analysis using micellar electrokinetic capillary chromatography. (A) Unseparated crude extract (diluted ten times); (B) cationic fraction; (C) anionic fraction; and (D) neutral unloaded fraction. Peaks marked in fraction B indicate non‐harmful peptides. Peaks marked in fraction D in the soya‐based sample indicate detectable levels of the isoflavones daidzein and genistein. The compounds are not quantified.