Modulation of chelating factors, trace minerals and their estimated bioavailability in Italian and African sorghum (Sorghum bicolor (L.) Moench) porridges

Abstract

Factors able to modulate chelating factors, trace minerals and their bioavailability were investigated in porridges of five sorghum (Sorghum bicolor (L.) Moench) varieties: from Nigeria, Senegal, Burkina Faso and two from Italy. Effects of variety and traditional fermentation and cooking were assessed on ironbinding phenolic groups, phytates and iron and zinc content and bioavailability. Chelating factors, trace elements as well as the effect of processing (mainly fermentation) were modulated by variety. Fermentation decreased iron-binding phenolic groups until 49% and phytate content until 72% as well as increased phytase activity 3.4-16.4 fold, leading to enhancement of iron and zinc estimated bioavailability. Cooking alone had almost no effect. The lowest chelating factors content and the highest trace minerals bioavailability were shown by fermented Senegal landrace, whereas the Italian varieties overall showed the worst results. The results indicate that selection of traditional varieties and appropriate processing methods can improve sorghum nutritional value.

Can fermentation be used as a sustainable strategy to reduce iron and zinc binders in traditional African fermented cereal porridges or gruels?

“…The reduction of PA in African fermented foods is highly varied with some finding no degradation (150,151) , less than 50% degradation (15,113,152,153) and others finding more than 50% degradation (15,112,113,(154)(155)(156) . Several factors seem to influence the reduction of mineral binders in these type of fermented foods.…”

“…(155) These differences clearly highlight that some matrices favor the reduction of PA than others. Proietti, et al (156) found PA degradation between 58 -72% of several fermented porridges produced from different sorghum varieties. The endogenous phytase activity of the sorghum flours varied between 0.17 -0.21 PU/g and increasing to 0.64 -3.44 PU/g in the fermented slurries and this demonstrates that PA reduction is also variety dependent.…”

“…Hurrell and coworkers (164) suggest that the molar ratio of PA/Fe should be <1 or optimally <0.4 for meals that are based on plain cereals and/or legumes with no enhancers of iron absorption such as ascorbic acid and meat. Table 5 (11,15,49,112,113,137,149,154,156,(165)(166)(167)(168) shows a list of the most common fermented porridges consumed in Africa along with their anti-nutrient content and PA/mineral ratios. Based on these ratios we can conclude that none of these porridges have the optimal PA/mineral ratio required for adequate iron and zinc absorption as such more efforts are required to improve mineral bioavailability.…”

Modulation of sorghum biological activities by varieties and two traditional processing methods: an integrated in vitro/modelling approach

“…Traditional sorghum processing such as fermentation or cooking may modulate the presence of chelating factors, hence nutrient bioavailability (Towo et al ., ; Abdelhaleem et al ., ). In a previous paper, we showed that chelating factors, trace elements as well as the effect of processing (mainly fermentation), were modulated by variety (Proietti et al ., ). In fermented samples, iron‐binding phenolic groups and phytate content decreased to a maximum of 49% and 72%, respectively; conversely, phytase activity increased 3.4–16.4 fold, leading to enhancement of iron and zinc estimated bioavailability.…”

“…The in vitro results were integrated by the iron bioavailability estimated through the use of the algorithm of Hallberg and Hultén (), as indicator of the modulation of sorghum nutritional value. The results are discussed in comparison with previous findings from analytical assays and molar ratios, which showed significant differences related to both variety and treatment (Proietti et al ., ).…”