Fermentation as a tool for increasing food security and nutritional quality of indigenous African leafy vegetables: the case of Cucurbita sp

Lactic Acid Fermentation Ameliorates Intrinsic Toxicants in Brassica campestris L. Leaves Harvested at Different Growth Stages

Brassica campestris (syn. Brassica rapa) is often known as mustard and is grown worldwide owing to its health-promoting characteristics associated with the presence of nutrients and phytochemicals. Along with the nutritional components, B. campestris also contains anti-nutrients (phytates, oxalates, tannins, alkaloids, saponins) that can cause adverse severe health effects to consumers, including rashes, nausea, headaches, bloating and nutritional deficiencies. In the present study, heating (blanching) and fermentation (Lactiplantibacillus plantarum) treatments were applied to reduce the load of the anti-nutrients of B. campestris leaves harvested at three different growth stages: the first stage (fourth week), the second stage (sixth week) and the third stage (eighth week). Results revealed that fermentation treatment using Lp. plantarum increases the ash (5.4 to 6%), protein (9 to 10.4%) and fiber (9.6 to 10.7%) contents, whereas moisture (0.91 to 0.82%), fat (9.9 to 9.1%) and carbohydrate (64.5 to 64.2%) contents decreased among B. campestris samples, and the trend was similar for all three stages. Blanching and fermentation lead to the reduction in phytates (46, 42%), saponins (34, 49%), tannins (1, 10%), oxalates (15, 7%) and alkaloids (10, 6%), separately as compared to raw samples of B. campestris leaves. In contrast, fermentation had no considerable effect on phytochemical contents (total phenolic and total flavonoids) and antioxidant potential (DPPH and FRAP). The action of blanching followed by fermentation caused more decline in the aforementioned toxicants load as compared to blanching or fermentation alone. Structural modifications in blanching and the biochemical conversions in fermentation lead to enhanced stability of nutrients and antioxidant potential. Taken together, these findings suggest blanching followed by fermentation treatments as a reliable, cost-effective and safer approach to curtail the anti-nutrient load without affecting the proximate composition, phytochemical attributes and antioxidant activity.

Fermented Vegetables: Health Benefits, Defects, and Current Technological Solutions

This review summarizes current studies on fermented vegetables, analyzing the changes in nutritional components during pickling, the health benefits of fermented vegetables, and their safety concerns. Additionally, the review provides an overview of the applications of emergent non-thermal technologies for addressing these safety concerns during the production and processing of fermented vegetables. It was found that vitamin C would commonly be lost, the soluble protein would degrade into free amino acids, new nutrient compositions would be produced, and the flavor correlated with the chemical changes. These changes would be influenced by the variety/location of raw materials, the original bacterial population, starter cultures, fermentation conditions, seasoning additions, and post-fermentation processing. Consuming fermented vegetables benefits human health, including antibacterial effects, regulating intestinal bacterial populations, and promoting health (anti-cancer effects, anti-diabetes effects, and immune regulation). However, fermented vegetables have chemical and biological safety concerns, such as biogenic amines and the formation of nitrites, as well as the existence of pathogenic microorganisms. To reduce hazardous components and control the quality of fermented vegetables, unique starter cultures, high pressure, ultrasound, cold plasma, photodynamic, and other technologies can be used to solve these problems.

Can consumption of local micronutrient- and absorption enhancer-rich plant foods together with starchy staples improve bioavailable iron and zinc in diets of at-risk African populations?

Iron and zinc deficiencies remain prevalent in developing countries, often due to monotonous starchy diets that are low in bioavailable minerals. This review addresses the question as to whether consumption of starchy staple foods in Africa together with micronutrient-dense and absorption enhancer-rich plant foods can enhance iron and zinc bioavailability in the diets of at-risk populations. While green leafy vegetables (GLVs) fortification of starchy staples can improve mineral contents, especially iron, it may not improve bioavailable iron and zinc, due to GLVs' high contents of mineral absorption inhibitors, notably polyphenols, phytate and calcium. Fruits, although low in minerals, could improve bioavailable iron and zinc in the staples because of their high ascorbic and citric acid and/or β-carotene contents, which can form soluble chelates with the minerals. More human studies are needed to establish whether such a technology or fortification strategy can improve bioavailable iron and zinc in African-type plant-based diets.

Agronomical valorization of eluates from the industrial production of microorganisms: Chemical, microbiological, and ecotoxicological assessment of a novel putative biostimulant

Plant Biostimulants (BSs) are a valid supplement to be considered for the integration of conventional fertilization practices. Research in the BS field keeps providing alternative products of various origin, which can be employed in organic and conventional agriculture. In this study, we investigated the biostimulant activity of the eluate obtained as a by-product from the industrial production of lactic acid bacteria on bare agricultural soil. Eluates utilization is in line with the circular economy principle, creating economical value for an industrial waste product. The research focused on the study of physical, chemical, biochemical, and microbiological changes occurring in agricultural soil treated with the biowaste eluate, applied at three different dosages. The final aim was to demonstrate if, and to what extent, the application of the eluate improved soil quality parameters and enhanced the presence of beneficial soil-borne microbial communities. Results indicate that a single application at the two lower dosages does not have a pronounced effect on the soil chemical parameters tested, and neither on the biochemical proprieties. Only the higher dosage applied reported an improvement in the enzymatic activities of β-glucosidase and urease and in the chemical composition, showing a higher content of total, nitric and ammonia N, total K, and higher humification rate. On the other hand, microbial communities were strongly influenced at all dosages, showing a decrease in the bacterial biodiversity and an increase in the fungal biodiversity. Bioinformatic analysis revealed that some Operative Taxonomic Units (OTUs) promoted by the eluate application, belong to known plant growth promoting microbes. Some other OTUs, negatively influenced were attributed to known plant pathogens, mainly Fusarium spp. Finally, the ecotoxicological parameters were also determined and allowed to establish that no toxic effect occurred upon eluate applications onto soil.

Evolution of microbial communities and nutritional content of fermented Amaranthus sp. leaves

Amaranth (Amaranthus sp.) is a promising indigenous leafy vegetable plant capable of contributing to food security in sub-Saharan Africa, thanks to its adaptability to diverse soils and its drought tolerance. Its edible parts such as leaves are characterized by high nutrient content. Food losses along the supply chain due to spoilage, however, especially of fresh produce is a challenge facing most of the sub-Saharan African countries in tackling food insecurity in the region. This calls for innovative yet inexpensive solutions such as natural fermentation to preserve the quality and safety of the commodity. To demonstrate the feasibility of natural fermentation in the preservation of vegetable amaranth, leaves were submerged (1:0.5 w/v) in distilled water with 3% sucrose and 3% NaCl dissolved. Control batches were prepared using only distilled water (1:0.5 w/v) with amaranth leaves. Samplings of both treated leaves and controls occurred at 0, 24, 48, 72, and 168 h to measure the pH and determine microbial population changes using culture and molecular-based techniques. Furthermore, the effects of treatment on nutritional content were assayed at the end of the process to determine the levels of B-group vitamins, β-carotene, lutein, and anti-nutrient phytic acid from unfermented fresh air-dried and 3% sucrose and 3% NaCl treated amaranth leaves. Finally, a visive and olfactive analysis was carried out to evaluate the acceptability of the final product. The significant drop of pH and the correct growth of Lactobacillaceae occurred only in treated batches, although Lactococcus was found in both treated and control samples. Furthermore, mean counts observed on selective media for controls and molecular high-throughput sequencing (HTS) analyses confirmed that in control samples, the undesired bacteria represented more than 60% of the microbial population. In treated amaranth leaves the amount of thiamin, riboflavin, vitamin B₆, β-carotene and lutein content were higher compared to the fresh unfermented air-dried leaves, and phytic acid content diminished after 7-days treatment. These findings suggest that treatment of amaranth leaves using 3% sucrose and 3% NaCl does not only preserve the commodity by arresting the growth of undesired microorganisms involved in spoilage and fosters the lactic acid bacteria but also improves the nutritional content of the fermented end product that has been warmly welcomed by panelists.