Effect of domestic processing and cooking methods on total, hcl extractable iron and in vitro availability of iron in spinach and amaranth leaves

A Comparison of Bioactive Metabolites, Antinutrients, and Bioactivities of African Pumpkin Leaves (Momordica balsamina L.) Cooked by Different Culinary Techniques

Prior to consumption, African pumpkin leaves (Momordica balsamina L.) are generally cooked. In this study, the effects of common household cooking methods (boiling, steaming, microwaving, stir-frying) on bioactive metabolites, carotenoids, antioxidant activity, antinutrients and inhibitory effects on α-glucosidase and α-amylase activities were examined. A set of 14 bioactive metabolites were identified in raw and cooked African leaves using UPLC-QTOF/MS. The results showed that the four different types of household cooking methods had different effects on the bioactive metabolomics profile of African pumpkin leaves. In comparison to raw leaves and leaves cooked in other methods, the concentrations of six phenolic compounds, rutin, cryptochlorogenic acid (4-caffeoylquinic acid), pseudolaroside A, isorhamnetin 3-O-robinoside, quercetin 3-galactoside, and trans-4-feruloylquinic acid, were highest in stir-fried leaves. Of all household cooking methods tested, stir-frying increased the content of lutein, β-carotene, and zeaxanthin by 60.00%, 146.15%, and 123.51%, respectively. Moreover, stir-frying African pumpkin leaves increased the antioxidant activity (DPPH and ABTS) and the inhibition of α-glucosidase and α-amylase. Compared to all four methods of household cooking, stir-frying reduced the antinutritive compounds compared to raw leaves. This work provides useful information to the consumers on the selection of suitable cooking methods for African pumpkin leaves.

Changes in antinutrients, phenolics, antioxidant activities and in vitro α-glucosidase inhibitory activity in pumpkin leaves (Cucurbita moschata) during different domestic cooking methods

Pumpkin leaves (Cucurbita moschata) were subjected to different household cooking methods (boiling, microwaving, steaming, and stir-frying) to evaluate their effect on antinutrients, phenolic compounds, antioxidant properties (ABTS, and DPPH) and in vitro α-glucosidase activity. All cooking methods studied significantly reduced the antinutrients and antioxidant activities, whilst phenolic compounds p-coumaric and ferulic acids significantly increased. The cooking methods reduced the oxalates by more than 50%, tannins by 47% and phytates by 79.22%. Steaming and boiling resulted in highest concentrations of p-coumaric (195.40 mg kg^-1) and ferulic acids (103.90 mg kg^-1) compared to other methods. Overall, boiled leaves retained the highest total phenolic compounds, whilst steamed leaves retained the highest antioxidant capacity. Raw pumpkin leaf extracts showed higher in vitro α-glucosidase inhibitory effects than the cooked leaves. Thus, cooking affected the inhibitory effect of in vitro α-glucosidase activity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-00916-w.

Iron species and proteins distribution in unconventional food plants

Abstract The sustainable food valorization is capable to stimulate the local products consumption with quality and nutritional security. In this scenario, Unconventional Food Plants (UFPs) deserve attention representing an alternative for rural communities and contributing to the local and regional economy. This work aimed to add nutritional information, once it evaluates total Fe concentration, Fe-species (water soluble, acid soluble, and inorganic), proteins, and Fe- proteins distribution in beldroega (Portulaca oleracea L.), guasca (Galinsoga parviflora Cav.), ora-pro-nóbis (Pereskia aculeata Mill.), piracá (Vernonia scorpioides (Lam.) Pers.), and trapoeraba (Commelina benghalensis L.). Considering the Fe total concentration, the studied UPFs can be excellent Fe sources, when compared to foods of plant origin widely consumed and cultivated, detaching the guasca leaves (687±19 µg g-1). However, the guasca leaves showed low concentration of Fe associated to macromolecules and Fe soluble species (1.6±0.3 µg g-1). These results may justify the low bioavailability of Fe species. On the other hand, beldroega leaves presented the highest concentration of inorganic Fe (1.3±0.2 µg g-1). In the UFPs, there is high glutelins concentration when compared to the other protein groups, meaning that UFPs can be low-cost alternative to supplementing protein intake. Finally, for majority UFPs, except guasca leaves, Fe is mainly associated to albumins, being a good source of bioavailable Fe species.

Uptake of vegetable and soft drink affected transformation and bioaccessibility of lead in gastrointestinal track exposed to lead-contaminated soil particles

Accidental ingestion of Pb-contaminated soil particles by direct hand-to-mouth activity or by swallowing airborne dust particles is important pathway of human exposure to Pb. Appropriate evaluation of Pb risk to human is important in determining whether the soil needs remediation or not, however, there is paucity of data about the dietary influences on Pb bioaccessibility (Pb-BA) and transformation in humans. This study chose two typical foods, spinach and cola, representing vegetable and soft drink, respectively, and investigated their effects on Pb species in gastrointestinal tract using the physiologically based extraction test. Results showed that ingestion of spinach and cola decreased the Pb-BA by 52%-94% in the gastric phase and by 38%-95% in the intestinal phase, respectively. The reduction of Pb-BA by spinach was attributed to the precipitation of Pb with phosphorus in spinach and the sorption of Pb by the generated hydrolysate and un-hydrolysate from spinach in gastrointestinal tract. Cola decreased Pb-BA mainly via formation of insoluble Pb phosphates precipitates. Analysis of X-ray diffraction and MINTEQ modeling demonstrated that the dissolved Pb was transformed to precipitated or sorbed Pb with intake of cola or spinach. Our findings suggest that dietary habit greatly influence the speciation and subsequent Pb-BA in the gastrointestinal tract, which should be incorporated into human health risk assessment of Pb-contaminated soil.

A Survey of Plant Iron Content-A Semi-Systematic Review

Iron is an essential mineral nutrient for all living organisms, involved in a plurality of biological processes. Its deficit is the cause of the most common form of anemia in the world: iron deficiency anemia (IDA). This paper reviews iron content in various parts of 1228 plant species and its absorption from herbal products, based on data collected from the literature in a semi-systematic manner. Five hundred genera randomly selected from the Angiosperms group, 215 genera from the Pteridophytes groups and all 95 Gymnosperm genera as listed in the Plant List version 1.1 were used as keywords together with the word "iron" in computerized searches. Iron data about additional genera returned by those searches were extracted and included in the analysis. In total, iron content values for a number of 1228 species, 5 subspecies, and 5 varieties were collected. Descriptive and inferential statistics were used to compare iron contents in various plant parts (whole plant, roots, stems, shoots, leaves, aerial parts, flowers, fruits, seeds, wood, bark, other parts) and exploratory analyses by taxonomic groups and life-forms were carried out. The absorption and potential relevance of herbal iron for iron supplementation are discussed.

Traditional food-processing and preparation practices to enhance the bioavailability of micronutrients in plant-based diets

Dietary quality is an important limiting factor to adequate nutrition in many resource-poor settings. One aspect of dietary quality with respect to adequacy of micronutrient intakes is bioavailability. Several traditional household food-processing and preparation methods can be used to enhance the bioavailability of micronutrients in plant-based diets. These include thermal processing, mechanical processing, soaking, fermentation, and germination/malting. These strategies aim to increase the physicochemical accessibility of micronutrients, decrease the content of antinutrients, such as phytate, or increase the content of compounds that improve bioavailability. A combination of strategies is probably required to ensure a positive and significant effect on micronutrient adequacy. A long-term participatory intervention in Malawi that used a range of these strategies plus promotion of the intake of other micronutrient-rich foods, including animal-source foods, resulted in improvements in both hemoglobin and lean body mass and a lower incidence of common infections among intervention compared with control children. The suitability of these strategies and their impact on nutritional status and functional health outcomes need to be more broadly assessed.

Iron solubility compared with in vitro digestion-Caco-2 cell culture method for the assessment of iron bioavailability in a processed and unprocessed complementary food for Tanzanian infants (6-12 months)

The Fe solubility test is a commonly used, easy and relatively cheap in vitro tool for predicting Fe bioavailability in food matrices. However, the outcome of a recent field trial comparing the effect on Fe status of Tanzanian infants of processed v. unprocessed complementary foods (CF), with otherwise the same composition, challenged the validity of this test for predicting Fe bioavailability. In the solubility test, significant more soluble Fe was observed in processed compared with unprocessed foods (mean 18.8 (sem 0.21) v. 4.8 (sem 0.23) %; P<0.001). However, in the field trial, no significant difference in Fe status was seen between processed and unprocessed CF groups after 6 months' follow-up. Therefore, twenty-four samples of these CF (twelve processed and twelve unprocessed batches) were analysed in triplicate for Fe availability using an in vitro digestion-Caco-2 cell culture method and results were compared with solubility results. Significantly more soluble Fe was presented to Caco-2 cells in the processed compared with unprocessed samples (mean 11.5 (sem 1.16) v. 8.5 (sem 2.54) %; P=0.028), but proportionally less Fe was taken up by the cells (mean 3.0 (sem 0.40) v. 11.7 (sem 2.22) %; P=0.007). As a net result, absolute Fe uptake was lower (not significantly) in processed compared with unprocessed CF (mean 1.3 (sem 0.16) v. 3.4 (sem 0.83) nmol/mg cell protein; P=0.052). These data clearly demonstrate that the Fe solubility test was not a good indicator of Fe bioavailability in these particular food matrices. In contrast, the results of an in vitro Caco-2 model supported the effects observed in vivo.