Challenges in the determination of unsubstituted food folates: impact of stabilities and conversions on analytical results

How food matrices modulate folate bioaccessibility: A comprehensive overview of recent advances and challenges

The incomplete absorption of dietary folate makes it crucial to understand how food matrices affect folate bioaccessibility. Bioavailability encompasses bioaccessibility, which depicts the proportion that is liberated from the food matrix during digestion and becomes available for absorption. Bioavailability studies are expensive and difficult to control, whereas bioaccessibility studies utilize in vitro digestion models to parameterize the complex digestion, allowing the evaluation of the effect of food matrices on bioaccessibility. This review covers the folate contents in various food matrices, the methods used to determine and the factors affecting folate bioaccessibility, and the advances and challenges in understanding how food matrices affect folate bioaccessibility. The methods for determining bioaccessibility have been improved in the last decade. Current research shows that food matrices modulate folate bioaccessibility by affecting the liberation and stability of folate during digestion but do not provide enough information about folate and food component interactions at the molecular level. In addition, information on folate interconversion and degradation during digestion is scant, hindering our understanding of the impact of food matrices on folate stability. Moreover, the role of conjugase inhibitors should not be neglected when evaluating the nutritional value of food folates. Due to the complexity of food digestion, holistic methods should be applied to investigate bioaccessibility. By synthesizing the current state of knowledge on this topic, this review highlights the lack of in-depth understanding of the mechanisms of how food matrices modulate folate bioaccessibility and provides insights into potential strategies for accurate evaluation of the nutritional value of dietary folate.

Folate-producing bifidobacteria: metabolism, genetics, and relevance

Folate (the general term for all bioactive forms of vitamin B9) plays a crucial role in the evolutionary highly conserved one-carbon (1C) metabolism, a network including central reactions such as DNA and protein synthesis and methylation of macromolecules. Folate delivers 1C units, such as methyl and formyl, between reactants. Plants, algae, fungi, and many bacteria can naturally produce folate, whereas animals, including humans, must obtain folate from external sources. For humans, folate deficiency is, however, a widespread problem. Bifidobacteria constitute an important component of human and many animal microbiomes, providing various health advantages to the host, such as producing folate. This review focuses on bifidobacteria and folate metabolism and the current knowledge of the distribution of genes needed for complete folate biosynthesis across different bifidobacterial species. Biotechnologies based on folate-trophic probiotics aim to create fermented products enriched with folate or design probiotic supplements that can synthesize folate in the colon, improving overall health. Therefore, bifidobacteria (alone or in association with other microorganisms) may, in the future, contribute to reducing widespread folate deficiencies prevalent among vulnerable human population groups, such as older people, women at child-birth age, and people in low-income countries.

Cereal-based fermented foods as a source of folate and cobalamin: The role of endogenous microbiota

Folate (vitamin B9) and cobalamin (vitamin B12) deficiencies potentially affect millions of people worldwide, leading to different pathologies. In Ethiopia, the diet is characterized by high consumption of fermented cereal-based foods such as injera, a good source of folate but not of cobalamin, which is only found in foods of animal origin that are rarely consumed. Some of the bacteria responsible for the fermentation of cereals can synthesize cobalamin, but whether or not fermented cereal food products contain cobalamin remains underexplored. The objective of this study was to assess the folate and cobalamin content of injera collected from various households in Ethiopia at different stages of production. Global (16S rRNA gene sequencing) and specific (real-time PCR quantification of bacteria known for folate or cobalamin production) bacterial composition of these samples was assessed. UPLC-PDA was used to identify the cobalamin to see whether the active or inactive form was present. Surprisingly, teff flour contained 0.8 μg/100 g of cobalamin, most probably due to microbial contamination from the environment and the harvesting process. While fermentation increased the folate and cobalamin content in some households, their levels decreased in others. Conversely, cooking consistently reduced the level of the vitamins. Fresh injera contained, on average, 21.2 μg/100 g of folate and 2.1 μg/100 g of cobalamin, which is high, but with marked variation depending on the sample. However, the form of cobalamin was a corrinoid that is biologically inactive in humans. Injera fermentation was dominated by lactic acid bacteria, with significant correlations observed between certain bacterial species and folate and cobalamin levels. For example, a high proportion of Fructilactobacillus sanfranciscensis, a known folate consumer, was negatively correlated with the folate content of injera. On the contrary, Lactobacillus coryniformis, known for its cobalamin synthesis ability was present in high proportion in the cobalamin-rich samples. These findings highlight the complex interrelationship between microorganisms and suggest the involvement of specific bacteria in the production of folate and cobalamin during injera fermentation. Controlled fermentation using vitamin-producing bacteria is thus a promising tool to promote folate and cobalamin production in fermented food.

Identification of quantitative trait loci and candidate genes for seed folate content in soybean

KEY MESSAGE

From 61 QTL mapped, a stable QTL cluster of 992 kb was discovered on chromosome 5 for folate content and a putative candidate gene, Glyma.05G237500, was identified. Folate (vitamin B9) is one of the most essential micronutrients whose deficiencies lead to various health defects in humans. Herein, we mapped the quantitative trait loci (QTL) underlying seed folate content in soybean using recombinant inbred lines developed from cultivars, ZH35 and ZH13, across four environments. We identified 61 QTL on 12 chromosomes through composite interval mapping, with phenotypic variance values ranging from 1.68 to 24.68%. A major-effect QTL cluster (qFo-05) was found on chromosome 5, spanning 992 kb and containing 134 genes. Through gene annotation and single-locus haplotyping analysis of qFo-05 in a natural soybean population, we identified seven candidate genes significantly associated with 5MTHF and total folate content in multiple environments. RNA-seq analysis showed a unique expression pattern of a hemerythrin RING zinc finger gene, Glyma.05G237500, between both parental cultivars during seed development, which suggest the gene might regulate folate content in soybean. This is the first study to investigate QTL underlying folate content in soybean and provides new insight for molecular breeding to improve folate content in soybean.

Health-Promoting Ingredients in Goat's Milk and Fermented Goat's Milk Drinks

The present study aimed to determine the content of health-promoting compounds, and fatty acids, with particular emphasis on the content of cis9trans11 C18:2 (CLA) acid, selected minerals, folates in organic and commercial goat's milk and fermented goat's milk drinks. The analyzed milk and yoghurts had various contents of particular groups of fatty acids, CLA, minerals, and folates. Raw organic goat's milk had a significantly (p < 0.05) higher content of CLA (3.26 mg/g fat) compared to commercial milk (2.88 mg/g fat and 2.54 mg/g fat). Among the analyzed fermented goat's milk drinks, the highest CLA content (4.39 mg/g fat) was determined in commercial natural yoghurts, while the lowest one was in organic natural yoghurts (3.28 mg/g fat). The highest levels of calcium (1322.9-2324.4 µg/g), phosphorus (8148.1-11,309.9 µg/g), and copper (0.072-0.104 µg/g) were found in all commercial products and those of manganese (0.067-0.209 µg/g) in organic products. The contents of the other assayed elements (magnesium, sodium, potassium, iron, and zinc) did not depend on the production method, but only on the product type, i.e., the degree of goat's milk processing. The highest folate content in the analyzed milks was found in the organic sample (3.16 µg/100 g). Organic Greek yoghurts had a several times higher content of folates, reaching 9.18 µg/100 g, compared to the other analyzed fermented products.

5-Methyltetrahydrofolate Is a Crucial Factor in Determining the Bioaccessibility of Folate in Bread

This study investigated the bioaccessibility of folate in wheat bread baked with different ingredients and processing methods. Next, different matrices were spiked with 5-methyltetrahydrofolate, gallic acid (GA), or both to investigate the stability of 5-methyltetrahydrofolate during in vitro digestion. The folate bioaccessibility in bread varied from 44 to 96%. The inclusion of whole-grain or faba bean flour significantly improved both folate content and bioaccessibility. Baking with yeast increased the folate content by 145% in bread but decreased folate bioaccessibility compared to the bread without added yeast because of the instability of 5-methyltetrahydrofolate. Spiking experiments confirmed oxidation as a critical reason for 5-methyltetrahydrofolate loss during digestion. However, GA protected this vitamer from degradation. Additionally, 5-methyltetrahydrofolate was less stable in whole-grain wheat matrices than other matrices. This study demonstrated that the stability of 5-methyltetrahydrofolate is crucial for folate bioaccessibility in bread, and methods for stabilizing this vitamer should be further studied.

Profiling of naturally occurring folates in a diverse soybean germplasm by HPLC-MS/MS

Soybean is a rich source of folates. We optimised the extraction and detection of folates from soybean seeds by HPLC-MS/MS and analysed the folate content and composition of 1074 accessions. Total folate content ranged from 64.51 to 691.24 μg/100 g fresh weight, with 10-fold variation, and 60 elite accessions with over 400 μg/100 g of total folate were identified. The most abundant component was 5-CHO-H4folate, which accounted for an average of 60% of total folate content. Seed-coat colour, seed weight, ecoregion, and accession type significantly affected soybean folate content. Furthermore, 5-CH3-H4folate correlated positively with seed protein (r = 0.24***) and negatively with oil (r = -0.26***). The geographical distribution of folate according to accession origin revealed that accessions from Northeast China contain higher amounts of total folate and 5-CHO-H4folate. This study provides comprehensive and novel insights into the folate profile of soybean, which will benefit soybean breeding for folate enhancement.

The Bioaccessibility of Folate in Breads and the Stability of Folate Vitamers during in vitro Digestion

Both the liberation and stability of endogenous folate are relevant to the bioaccessibility of folate. Since folates are unstable, in addition to studying the natural folate content in foods, bioaccessibility...

Changes in the Folate Content and Fatty Acid Profile in Fermented Milk Produced with Different Starter Cultures during Storage

The application of bacterial cultures in food fermentation is a novel strategy to increase the “natural” levels of bioactive compounds. The unique ability of lactic acid bacteria (LAB) to produce folate, B vitamins, and conjugated linolenic acid cis9trans11 C18:2 (CLA) during cold storage up to 21 days was studied. Although some species of LAB can produce folates and other important nutrients, little is known about the production ability of yogurt starter cultures. Pasteurized milk samples were inoculated with four different combinations of commercially available yogurt vaccines, including starter cultures of Bifidobacterium bifidum. Both the type of vaccine and the time of storage at 8 °C had a significant effect on the folate and CLA contents in the tested fermented milks. The highest folate content (105.4 µg/kg) was found in fresh fermented milk inoculated with Lactobacillus delbrueckii, Streptococcus thermophilus, and Bifidobacterium bifidum. Only the mix of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and Bifidobacterium bifidum showed potential (59% increase) to synthesize folate during seven days of storage. A significant increase in the content of CLA, when compared to fresh fermented milk, was observed during cold storage for up to 21 days in products enriched with Bifidobacterium bifidum.

Validated B vitamin quantification from lentils by selected reaction monitoring mass spectrometry

A validated method for B vitamin separation and quantification from lentil seeds using ultra high performance liquid chromatography-selected reaction monitoring mass spectrometry (UHPLC-SRM MS) was reported. The use of three enzymes (acid phosphatase, β-glucosidase, and rat serum) with a 4 h incubation was sufficient to convert bound B vitamins into their free forms. Twenty B vitamers were selected and a 5-min UHPLC-SRM MS method was optimized for rapid analysis. This method was applied to quantify B vitamin concentration during lentil seed germination over a 5-day period. Total B vitamins increased up to 1.5-fold on day 5 (from 39.2 µg/g to 60.6 µg/g of dry weight) comparing with dry seeds. Vitamin B5 (pantothenic acid) was the most abundant B vitamin in both dry seeds (34.2%) and in germinated seeds (17.7%-24.5% of total B vitamins); B8 (biotin) and B12 (cyanocobalamin) were not detected in lentil samples.

Collaborative study: Quantification of total folate in food using an efficient single-enzyme extraction combined with LC-MS/MS

Quantification of the specific folate vitamers to estimate total folate in foods is not standardized. A collaborative study, including eight European laboratories, was conducted in order to determine the repeatability and reproducibility of the method for folate quantification in foods using the plant-origin γ-glutamyl hydrolase as part of the extraction procedure. The seven food samples analyzed represent the food groups; fruits, vegetables, dairy products, legumes, offal, fish, and fortified infant formula. The homogenization step was included, and six folate vitamers were analyzed using LC-MS/MS. Total folate content, expressed as folic acid equivalent, was 17-490 μg/100 g in all samples. Horwitz ratio values were within the acceptable range (0.60-1.94), except for fish. The results for fortified infant formula, a certified reference material (NIST 1869), confirmed the trueness of the method. The collaborative study is part of a standardization project within the Nordic Committee on Food Analysis (NMKL).

Modified EMR-lipid method combined with HPLC-MS/MS to determine folates in egg yolks from laying hens supplemented with different amounts of folic acid

Egg yolks are a good source of folates. However, the method for analyzing the naturally occurring folates in egg yolks is complicated and time-consuming. In this study, a simplified pre-treatment method followed by validated HPLC-MS/MS was developed to determine native folates in eggs from laying hens treated with different amounts of folic acid. The modified enhanced matrix removal -lipid method to purify samples showed good performance in lipid elimination, reduction of steps and time savings. According to experimental analysis, yolks contained total folate amounts ranging from 147 to 760 μg/100 g when laying hens' diet was supplemented with folic acid from 0 to 10 mg/kg. Four folate vitamers were detected in egg yolks: 5-methyltetrahydrofolate accounted for 91-98% of total folates, whereas folic acid, 5-formyltetrahydrofolate and 10-formylfolic acid together accounted for 2-9%. Therefore, laying hens efficiently converted folic acid in feed into 5-methyltetrahydrofolate in eggs with little folic acid deposition.

Comprehensive Vitamer Profiling of Folate Mono- and Polyglutamates in Baker's Yeast (Saccharomyces cerevisiae) as a Function of Different Sample Preparation Procedures

Folates are a group of B9 vitamins playing an important role in many metabolic processes such as methylation reactions, nucleotide synthesis or oxidation and reduction processes. However, humans are not able to synthesize folates de novo and thus rely on external sources thereof. Baker's yeast (Saccharomyces cerevisiae) has been shown to produce high amounts of this vitamin but extensive identification of its folate metabolism is still lacking. Therefore, we optimized and compared different sample preparation and purification procedures applying solid phase extraction (SPE). Strong anion exchange (SAX), C18 and hydrophilic-lipophilic-balanced (HLB) materials were tested for their applicability in future metabolomics studies. SAX turned out to be the preferred material for the quantitative purification of folates. Qualification of several folate vitamers was achieved by ultra-high pressure liquid chromatography quadrupole time of flight mass spectrometry (UHPLC-Q-ToF-MS) measurements and quantification was performed by liquid chromatography tandem mass spectrometry (LC-MS/MS) applying stable isotope dilution assays (SIDAs). The oxidation product s-pyrazino-triazine (MeFox) was included into the SIDA method for total folate determination and validation. Applying the best protocol (SAX) in regard to folate recovery, we analyzed 32 different vitamers in different polyglutamate states up to nonaglutamates, of which we could further identify 26 vitamers based on tandem-MS (MS2) spectra. Total folate quantification revealed differences in formyl folate contents depending on the cartridge chemistry used for purification. These are supposedly a result of interconversion reactions occurring during sample preparation due to variation in pH adjustments for the different purification protocols. The occurrence of interconversion and oxidation reactions should be taken into consideration in sample preparation procedures for metabolomics analyses with a focus on folates.

Folate content and retention in wheat grains and wheat-based foods: Effects of storage, processing, and cooking methods

Folates are essential micronutrients for human health. The aim of this study was to evaluate the effects of storage, processing and cooking methods on folate content and identify factors with great influence on folate retention in wheat grains and wheat-based foods. For this, the folate levels of wheat grains after 2-8 months of storage, wheat flours, noodles, fermented dough, steamed bun, and bread were sequentially analyzed. An average of 26% folate loss was observed after eight-month storage in wheat grains. The milling process, with an extraction rate of 70%, led to a severe (71%) folate loss. The folate retention rate in noodles was 78%. Fermentation by yeast production enabled a 1.5-4-fold enhancement of folate levels in steamed bun and bread. Boiling, steaming and baking led to a folate loss of 13%, 16%, and 11%, respectively. These results help to guide industrial/household preparation of wheat-based foods for folate nutrition.

Influence of storage conditions and packaging of fortified wheat flour on microbial load and stability of folate and vitamin B12

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Fortified flours were stored for 6 months at controlled temperature and humidity.

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Well-packaged flours were stable up to 6 months whatever the storage conditions.

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Vitamins B9 and B12 were mostly affected by the permeability of the packaging.

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In low-quality packaging, vitamins were affected by relative humidity variations.

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In low-quality packaging, flour microbial quality was impacted when stored at 85% RH.

Flour fortification with folic acid (FA) is implemented in many countries, and the fortification of flour with vitamin B12 has been planned. However, vitamins losses can occur during storage. In this study, fortified wheat flour was packaged either in paper bags or multilayer aluminum/PET bags, and stored in controlled conditions of temperature (25 °C or 40 °C) and relative humidity (65% or 85% RH) for 6 months. FA content, cyanocobalamin content, and microbial quality were regularly assessed. In flours packed in multilayer bags (non-permeable to oxygen and humidity), no significant FA and cyanocobalamin losses were observed, irrespective of temperature and RH. In flours packed in permeable paper bags, the microbial quality deteriorated in flours stored at 85% RH, FA loss reached 22–53% after 6 months at 85% RH, whereas cyanocobalamin loss reached 49–63% after 6 months at 65% RH. This shows that, depending on environmental conditions, packaging choice is of critical importance.

Folate content analysis of wheat cultivars developed in the North China Plain

Folates are essential micronutrients in the human diet. Germplasm rich in folates can be used as genetic resource for diet and breeding to produce new varieties with enhanced folates. To investigate the natural variation of folates among wheat cultivars and identify high folate materials for breeding, we studied the grain folate contents of 360 wheat samples consisting of 315 wheat genotypes grown in North China using the high performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS) method. The total folate content among wheat genotypes ranged from 10.15 ± 2.86 to 91.44 ± 5.64 µg per 100 g grains, thus showing a remarked variation. Fifty-two wheat cultivars, such as Henong58-3, were identified as good sources of folates. 5-Formyltetrahydrate and 5-methyltetrahydrate were found to be the two major folate derivatives in wheat germplasm. In addition, we found that environment factor also had significant effect on folate production. This investigation can help wheat breeders for folate improvement.

Quantification of Cellular Folate Species by LC-MS after Stabilization by Derivatization

Folate cofactors play a key role in one-carbon metabolism. Analysis of individual folate species is hampered by the low chemical stability and high interconvertibility of folates, which can lead to severe experimental bias. Here, we present a complete workflow that employs simultaneous extraction and stabilization of folates by derivatization. We perform reductive methylation employing stable isotope labeled reagents to retain information on the position and redox state of one-carbon units as well as the redox state of the pteridine ring. The derivatives are analyzed by a targeted LC(HILIC)-MS/MS method without the need for deconjugation, thereby also preserving the glutamation state of folates. The presented method does not only improve analyte coverage and sensitivity as compared to other published methods, it also greatly simplifies sample handling and storage. Finally, we report differences in the response of bacterial and mammalian systems to pharmacological inhibition of dihydrofolate reductase.

Recent Developments in Folate Nutrition

The term folate (vitamin B9) refers to a group of water-soluble compounds that are nutritionally essential for the support of optimal human health and development. Folates participate in numerous one-carbon transfer reactions, including the methylation of important biomolecules (lipids, amino acids, DNA). A deficiency of folate leads to pathological outcomes including anemia and impairments in reproductive health and fetal development. Due to the linkage of impaired folate status with an increased prevalence of neural tube defects (NTDs) in babies, several jurisdictions required the fortification of the food supply with folic acid, a synthetic and stable form of folate. Data from the postfortification era have provided strong evidence for the reduction of NTDs due to folic acid fortification. However, concern is now growing with respect to the amount of synthetic folic acid within the human food supply. Excess folic acid intake has been linked to a masking of vitamin B12 deficiency, and concerns regarding the promotion of folate-sensitive cancers, including colorectal cancer. New strategies to ensure the supply of optimal folate to at-risk populations may be needed, including the use of biofortification approaches, in order to address recent concerns.

Lactic acid fermentation as a tool for increasing the folate content of foods

Folate is an essential micronutrient involved in numerous vital biological reactions. The dietary consumption of naturally occurring vitamin B9 is often inadequate in many countries, and supplementation or fortification programs (using synthetic folic acid) are implemented to alleviate folate deficiency. Other food-based alternatives are possible, such as the use of lactic acid bacteria (LAB) to synthesize folate during fermentation. Many studies have been conducted on this topic, and promising results were reported for some fermented dairy products. However, in other studies, folate consumption by LAB or rather low folate production were observed, resulting in fermented foods that may not significantly contribute to the recommended B9 intake. In addition, the optimum conditions for folate biosynthesis by LAB are still not clear. The aim of this review was thus to (i) clarify the ability of LAB to produce folate in food products, (ii) check if the production of folate by LAB in various fermented foods is sufficient to meet human vitamin B9 requirements and (iii) suggest ways to optimize folate production by LAB in fermented food products.

Influence of fermentation and other processing steps on the folate content of a traditional African cereal-based fermented food

Folate deficiency can cause a number of diseases including neural tube defects and megaloblastic anemia, and still occurs in both developed and developing countries. Cereal-based food products are staple foods in many countries, and may therefore be useful sources of folate. The production of folate by microorganisms has been demonstrated in some cereal-based fermented foods, but has never been studied in a traditional African cereal based food spontaneously fermented. The microbiota of ben-saalga, a pearl-millet based fermented porridge frequently consumed in Burkina Faso, has a good genetic potential for the synthesis of folate, but the folate content of ben-saalga is rather low, suggesting that folate is lost during the different processing steps. The aim of this study was therefore to monitor changes in folate content during the different steps of preparing ben-saalga, from pearl-millet grains to porridge. Traditional processing involves seven different steps: washing, soaking, grinding, kneading, sieving, (spontaneous) fermentation, and cooking. Two type of porridge were prepared, one using a process adapted from the traditional process, the other a modified process based on fermentation by backslopping. Dry matter and total folate contents were measured at each step, and a mass balance assessment was performed to follow folate losses and gains. Folate production was observed during the soaking of pearl-millet grains (+26% to +79%), but the folate content of sieved batters (2.5 to 3.4μg/100g fresh weight) was drastically lower than that of milled soaked grains (17.3 to 19.4μg/100g FW). The final folate content of the porridges was very low (1.5 to 2.4μg/100g FW). The fermentation had no significant impact on folate content, whatever the duration and the process used. This study led to a better understanding of the impact on folate of the different processing steps involved in the preparation of ben-saalga.

Folates in Plants: Research Advances and Progress in Crop Biofortification

Folates, also known as B9 vitamins, serve as donors and acceptors in one-carbon (C1) transfer reactions. The latter are involved in synthesis of many important biomolecules, such as amino acids, nucleic acids and vitamin B5. Folates also play a central role in the methyl cycle that provides one-carbon groups for methylation reactions. The important functions fulfilled by folates make them essential in all living organisms. Plants, being able to synthesize folates de novo, serve as an excellent dietary source of folates for animals that lack the respective biosynthetic pathway. Unfortunately, the most important staple crops such as rice, potato and maize are rather poor sources of folates. Insufficient folate consumption is known to cause severe developmental disorders in humans. Two approaches are employed to fight folate deficiency: pharmacological supplementation in the form of folate pills and biofortification of staple crops. As the former approach is considered rather costly for the major part of the world population, biofortification of staple crops is viewed as a decent alternative in the struggle against folate deficiency. Therefore, strategies, challenges and recent progress of folate enhancement in plants will be addressed in this review. Apart from the ever-growing need for the enhancement of nutritional quality of crops, the world population faces climate change catastrophes or environmental stresses, such as elevated temperatures, drought, salinity that severely affect growth and productivity of crops. Due to immense diversity of their biochemical functions, folates take part in virtually every aspect of plant physiology. Any disturbance to the plant folate metabolism leads to severe growth inhibition and, as a consequence, to a lower productivity. Whereas today's knowledge of folate biochemistry can be considered very profound, evidence on the physiological roles of folates in plants only starts to emerge. In the current review we will discuss the implication of folates in various aspects of plant physiology and development.

PCR screening of an African fermented pearl-millet porridge metagenome to investigate the nutritional potential of its microbiota

Cereals are staple foods in most African countries, and many African cereal-based foods are spontaneously fermented. The nutritional quality of cereal products can be enhanced through fermentation, and traditional cereal-based fermented foods (CBFFs) are possible sources of lactic acid bacteria (LAB) with useful nutritional properties. The nutritional properties of LAB vary depending on the species and even on the strain, and the microbial composition of traditional CBFFs varies from one traditional production unit (TPU) to another. The nutritional quality of traditional CBFFs may thus vary depending on their microbial composition. As the isolation of potentially useful LAB from traditional CBFFs can be very time consuming, the aim of this study was to use PCR to assess the nutritional potential of LAB directly on the metagenomes of pearl-millet based fermented porridges (ben-saalga) from Burkina Faso. Genes encoding enzymes involved in different nutritional activities were screened in 50 metagenomes extracted from samples collected in 10 TPUs in Ouagadougou. The variability of the genetic potential was recorded. Certain genes were never detected in the metagenomes (genes involved in carotenoid synthesis) while others were frequently detected (genes involved in folate and riboflavin production, starch hydrolysis, polyphenol degradation). Highly variable microbial composition - assessed by real-time PCR - was observed among samples collected in different TPUs, but also among samples from the same TPU. The high frequency of the presence of genes did not necessarily correlate with in situ measurements of the expected products. Indeed, no significant correlation was found between the microbial variability and the variability of the genetic potential. In spite of the high rate of detection (80%) of both genes folP and folK, encoding enzymes involved in folate synthesis, the folate content in ben-saalga was rather low (median: 0.5μg/100g fresh weight basis). This work highlighted the limit of evaluating the nutritional potential of the microbiota of traditional fermented foods by the only screening of genes in metagenomes, and suggests that such a screening should be completed by a functional analysis.

Folates: Chemistry, analysis, occurrence, biofortification and bioavailability

Folates (Vitamin B₉) include both naturally occurring folates and synthetic folic acid used in fortified foods and dietary supplements. Folate deficiency causes severe abnormalities in one-carbon metabolism can result chronic diseases and developmental disorders, including neural tube defects. Mammalian cells cannot synthesize folates de novo; therefore, diet and dietary supplements are the only way to attain daily folate requirements. In the last decade, significant advancements have been made to enhance the folate content of rice, tomato, common bean and lettuce by using genetic engineering approaches. Strategies have been developed to improve the stability of folate pool in plants. Folate deglutamylation through food processing and thermal treatment has the potential to enhance the bioavailability of folate. This review highlights the recent developments in biosynthesis, composition, bioavailability, enhanced production by elicitation and metabolic engineering, and methods of analysis of folate in food. Additionally, future perspectives in this context are identified. Detailed knowledge of folate biosynthesis, degradation and salvage are the prime requirements to efficiently engineer the plants for the enhancement of overall folate content. Similarly, consumption of a folate-rich diet with enhanced bioavailability is the best way to maintain optimum folate levels in the body.

Inhibition of Photodegradation of Highly Dispersed Folic Acid Nanoparticles by the Antioxidant Effect of Transglycosylated Rutin

We developed highly dispersible and photostable nanoparticles of vitamin, folic acid (FA). FA was wet bead milled with milling and dispersing adjuvants and transglycosylated compounds such as α-glucosyl hesperidin (Hesperidin-G) and rutin (Rutin-G), which solubilized FA. The milled slurries of FA particles with transglycosylated compounds consisted of nanosized particles with a median diameter of <100 nm. The lyophilized formulations of these slurries retained their nanometer size after resuspension in water with no aggregation. The apparent solubility of FA in these formulations was 100-fold higher than that of untreated FA. The solubilizing effect of Rutin-G may affect the particle size reduction and dispersibility of FA. The photostability results showed that the strong antioxidant activity of Rutin-G substantially increased the photostability of FA solution. On the basis of these results, bead milling of FA with Rutin-G is a promising technique for developing highly dispersible, photostable nanoparticle FA formulations.

Folates in Fruits and Vegetables: Contents, Processing, and Stability

Folates play a key role in human one-carbon metabolism and are provided by food. It is well established that folates are beneficial in the prevention of neural tube defects and cardiovascular and neurodegenerative diseases. Fruits and vegetables, and especially green vegetables, are the main sources of folates. In parallel, fruits and vegetables, with high contents of folates, are mostly consumed after processing, such as, canning, freezing, or home-cooking, which involve folate losses during their preparation. Hence, it is important to know the percentage of folate losses during processing and, moreover, the mechanisms underlying those losses. The current knowledge on folate losses from fruit and vegetables are presented in this review. They depend on the nature of the respective fruit or vegetable and the respective treatment. For example, steaming involves almost no folate losses in contrast to boiling. Two main mechanisms are involved in folate losses: (i) leaching into the surrounding liquid and (ii) oxidation during heat treatment, the latter of which depending on the nature of the vitamer considered. In this respect, a vitamer stability decreases in the order starting from folic acid followed by 5-HCO-H₄ folate, 5-CH₃ -H₄ folate, and, finally, H₄ folate. Further studies are required, especially on the diffusion of the vitamers in real foods and on the determination of folate degradation products.