Bound phenolics in foods, a review

Oxidative stress, a result of an overproduction and accumulation of free radicals, is the leading cause of several degenerative diseases such as cancer, atherosclerosis, cardiovascular diseases, ageing and inflammatory diseases. Polyphenols form an important class of naturally occurring antioxidants, having innumerable biological activities such as anticancer, antifungal, antibacterial, antiviral, antiulcer and anticholesterol, to name a few. Among various polyphenols, gallic acid (3,4,5-trihydroxybenzoic acid), a naturally occurring low molecular weight triphenolic compound, has emerged as a strong antioxidant and an efficient apoptosis inducing agent. Starting from the bioavailability and the biosynthetic pathway of gallic acid, this review includes various in vitro, in vivo and in silico studies providing the mode of action, radical scavenging activity, ability to inhibit lipid peroxidation, maintenance of endogenous defense systems and metal ion chelation by this triphenolic molecule, along with a comprehensive overview of factors responsible for its high antioxidant activity. Gallic acid derivatives have also been found in a number of phytomedicines with diverse biological and pharmacological activities, including radical scavenging, interfering with the cell signaling pathways and apoptosis of cancer cells. The diverse range of applications of this simple polyphenol is due to a fine amalgam between its antioxidant and prooxidant potential. The existing literature on this dual behavior of gallic acid and its derivatives is reviewed here. This is followed by an account of their potential clinical and industrial applications.

Gallic acid: a versatile antioxidant with promising therapeutic and industrial applications

Zinc and iron oxide nanoparticles improved the plant growth and reduced the oxidative stress and cadmium concentration in wheat.

Legumes and cereals contain high amounts of macronutrients and micronutrients but also anti-nutritional factors. Major anti-nutritional factors, which are found in edible crops include saponins, tannins, phytic acid, gossypol, lectins, protease inhibitors, amylase inhibitor, and goitrogens. Anti-nutritional factors combine with nutrients and act as the major concern because of reduced nutrient bioavailability. Various other factors like trypsin inhibitors and phytates, which are present mainly in legumes and cereals, reduce the digestibility of proteins and mineral absorption. Anti-nutrients are one of the key factors, which reduce the bioavailability of various components of the cereals and legumes. These factors can cause micronutrient malnutrition and mineral deficiencies. There are various traditional methods and technologies, which can be used to reduce the levels of these anti-nutrient factors. Several processing techniques and methods such as fermentation, germination, debranning, autoclaving, soaking etc. are used to reduce the anti-nutrient contents in foods. By using various methods alone or in combinations, it is possible to reduce the level of anti-nutrients in foods. This review is focused on different types of anti-nutrients, and possible processing methods that can be used to reduce the level of these factors in food products. A brief overview of beneficial effects of anti-nutrients and reduction strategy.

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Plant food anti-nutritional factors and their reduction strategies: an overview

Lactobacillus plantarum (widespread member of the genus Lactobacillus) is one of the most studied species extensively used in food industry as probiotic microorganism and/or microbial starter. The exploitation of Lb. plantarum strains with their long history in food fermentation forms an emerging field and design of added-value foods. Lb. plantarum strains were also used to produce new functional (traditional/novel) foods and beverages with improved nutritional and technological features. Lb. plantarum strains were identified from many traditional foods and characterized for their systematics and molecular taxonomy, enzyme systems (α-amylase, esterase, lipase, α-glucosidase, β-glucosidase, enolase, phosphoketolase, lactase dehydrogenase, etc.), and bioactive compounds (bacteriocin, dipeptides, and other preservative compounds). This review emphasizes that the Lb. plantarum strains with their probiotic properties can have great effects against harmful microflora (foodborne pathogens) to increase safety and shelf-life of fermented foods.

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Lactobacillus plantarum with Functional Properties: An Approach to Increase Safety and Shelf-Life of Fermented Foods.

Phytate, phenolic compounds and fiber are known anti-nutritional factors (ANFs) that contribute to the low bioaccessibility and bioavailability of iron and zinc in plant foods. Better insight into the localization of minerals and anti-nutritional factors in plant tissues, as well as on the mechanisms of interaction between minerals and ANFs, may lead to better targeted processing for improvement of the bioaccessibility of minerals in plant foods. This review highlights the subcellular distribution of iron and zinc and their ANFs in plant organs, as well as the mechanisms of interaction between these metals and their ANFs. These insights are then used to better clarify the role of various processing technologies, like mechanical treatments, soaking, germination, fermentation and heating, on improving the bioaccessibility of iron and zinc in plant foods.

Role of processing on bioaccessibility of minerals: Influence of localization of minerals and anti-nutritional factors in the plant

BACKGROUND: Food-isolated lactic acid bacteria can transform ferulic acid (FA) into several products. Since quantification of these metabolites during the different bacterial growth phases is lacking, the aim of this study was to identify and quantify conversion products of FA and to follow the kinetics of FA metabolism during growth of Lactobacillus plantarum and Lactobacillus collinoides.



RESULTS: Lactobacillus plantarum and Lactobacillus collinoides were incubated in MRS broth, to which different amounts of FA were added (final concentrations of 0, 0.5, 1.5 and 3 mmol L−1), at 30 °C until the late stationary phase. Lactobacillus plantarum metabolised FA into 4-vinylguaiacol (4-VG) and hydroferulic acid (HFA). Conversion to 4-VG started simultaneously with the degradation of FA, while formation of HFA started in the mid-exponential phase. Lactobacillus collinoides only formed 4-VG, mainly in the stationary phase. No significant effect of the different amounts of FA was seen on the growth and fermentation characteristics of both bacteria.



CONCLUSION: The results demonstrate that both bacteria are able to convert FA. However, start of conversion differs between the two strains. The different amounts of FA had no influence on the growth and fermentation characteristics of both bacteria. Copyright © 2012 Society of Chemical Industry

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Metabolism of ferulic acid during growth of Lactobacillus plantarum and Lactobacillus collinoides

Plant products are rich in minerals, e.g. iron, as well as in phenolic acids, e.g. gallic acid (GA). GA contains a galloyl group leading to complexation with iron, and thus decreasing the bioavailability of iron. As complexation of GA–iron seems to be pH-dependent, lactic acid fermentation could be a technique to improve the bioavailability of iron. On the other hand different lactobacillus strains are able to metabolize GA into pyrogallol (PYR). In this study, the influence of pH and microbial conversion of GA on iron complexation during fermentation with Lactobacillus plantarum and Lactobacillus collinoides was investigated. PYR was detected as the only conversion product of GA. At the end of the fermentations, a decreased pH to 5 and 5.7 for L. plantarum and L. collinoides respectively was measured. Based on the colour change during fermentation and based on the spectrophotometric analysis with standards, complexation between iron and GA or PYR was established. From the results, it could be concluded that the effect of pH on complexation was more pronounced compared to the microbial conversion of GA. Based on these results, L. plantarum is an efficient bacteria to destabilize the formed complexes which could lead to an improved bioavailability of iron.

Influence of microbial conversion and change in pH on iron–gallic acid complexation during lactobacillus fermentation

During the production of vegetables, a lot of waste is produced. This waste still contains a high amount of important health beneficial compounds, e.g. phenolic compounds. Phenolic compounds in cabbage leaves appear in their bound form, conjugated with mono- and polysaccharides and/or linked to one or more of the phenolic groups. Several techniques are studied to release the phenolic compounds from these leaves. One possible processing technique is the use of lactic acid fermentation to release phenolic compounds from cabbage leaves. Therefore, cabbage leaves were mixed with sterile water and transferred into jars. Three heat treatments i.e. pasteurization, sterilization and no heat treatment, were performed on the leaves, combined with three different starters i.e. Lactobacillus plantarum, Lactobacillus collinoides and natural fermentation. The jars were incubated for 13 days at 30 °C and sampled on a regular base to follow growth and phenolic profile. Independent of the performed heat treatment, the pH increased during natural fermentation. In the incubations with L. plantarum, the pH immediately decreased, independent of the heat treatment. In a later stage of the fermentation, an increase in pH was monitored. For the incubations with L. collinoides, independent of the thermal treatment, the decrease in pH was at a later moment in time. In the case were no heat treatment was subjected to the leaves, an increase of pH was seen after 50 hours of fermentation. In the two other heat treated samples, inoculated with L. collinoides, the pH remained more or less constant. LC-analysis after acid hydrolysis of the fermented leaves showed clearly the release of 3 compounds. One of these compounds is identified as kaempferol. The amount of kaempferol stayed constant during fermentation. The other two peaks needs to be identified further and were degraded by the present microflora.

Potential of lactic acid fermentation to produce health beneficial compounds from vegetable waste

https://biblio.ugent.be/publication/1935355/file/1936265.pdf

Dries Knockaert

Papers

Role of processing on bioaccessibility of minerals: Influence of localization of minerals and anti-nutritional factors in the plant

Metabolism of ferulic acid during growth of Lactobacillus plantarum and Lactobacillus collinoides

Influence of microbial conversion and change in pH on iron–gallic acid complexation during lactobacillus fermentation

Potential of lactic acid fermentation to produce health beneficial compounds from vegetable waste

Metabolism of ferulic acid during growth of Lactobacillus plantarum and Lactobacillus collinoides