Bound phenolics in foods, a review

Heat treatment as postharvest tool for improving quality in extra-early nectarines

BACKGROUND

Extra-early nectarine cultivars such as 'VioWhite 5' could present a lack of organoleptic and nutritional quality. Heat treatments (HT) can be applied to improve their primary characteristics. In this experiment, control (non-treated), HT₁ (3 h; 45 °C) and HT₂ (2 h; 50 °C) were studied. Fruit were stored (10 days; 0 ± 0.5 °C; 90-95% RH) followed by a simulated retail sale period (3 days; 15 °C; 70-75% RH).

RESULTS

HT fruit showed higher weight loss (2.76 ± 0.06% and 3.32 ± 0.01% for HT₁ and HT₂ , respectively; vs. 2.23 ± 0.14% for control) and lower firmness than control samples (28.88% and 21.67% less for HT₁ and HT₂ , respectively). HT treatments induced an increase in soluble solids content and a decrease in total acidity, which led to a better sensory quality. These changes were positively received by consumers. Total antioxidant capacity was enhanced by HT due to an increase in phenolic compound content. A higher enzymatic activity was found in pectin methylesterase and polygaracturonase in HT nectarines when compared to control.

CONCLUSION

The application of HT on extra-early nectarine cv. demonstrated a strong potential to improve consumption quality in the industry. © 2017 Society of Chemical Industry.

The Nutritional and Phytochemical Composition of the Indigenous Australian Pindan Walnut (Terminalia cunninghamii) Kernels

Nutritional composition of the kernels of two types of Pindan walnut (Terminalia cunninghamii), a native nut consumed traditionally by Australian Indigenous peoples, is reported for the first time. Results showed that Pindan walnut kernels contained high levels of fat, protein and ash, approximately 50, 30 and 5% fresh basis, respectively. The levels of minerals in the kernels were much higher than common walnuts and macadamia nuts, especially those of phosphorus, magnesium and zinc. The high amounts of polyphenols in the kernels provided strong hydrophilic antioxidant capacities, of up to 2004 mg Trolox equivalents/100 g fresh basis using the hydrophilic oxygen radical absorbance capacity assay. Both free polyphenol content and hydrophilic antioxidant capacities of the kernels were higher than those of macadamia nuts, although the lipophilic oxygen radical absorbance capacity was lower. These preliminary studies indicate high potential for wider use of the Pindan walnut as a novel, nutritious and health-promoting food.

Arabinoxylans from rice bran and wheat immunomodulatory potentials: a review article

Purpose

The purpose of this study is to discuss recent research on arabinoxylans from rice bran and wheat byproducts and their immunomodulatory potentials. Also, a potential receptor for arabinoxylans is proposed in relation to arabinoxylans structure.

Design/methodology/approach

This review summarises recent publications on arabinoxylans from rice bran and wheat, classification of arabinoxylans, a brief background on their method of extraction and their immunomodulatory potentials as they induce pro-inflammatory response in vitro, in vivo and in humans. The mechanism of action in which arabinoxylans modulate the immune activity is yet to be discovered, However, the authors have proposed a potential receptor for arabinoxylans in relation to arabinoxylans structure and molecular weight.

Findings

The effects of arabinoxylans from rice bran and wheat on the immune response was found to cause a pro-inflammatory response in vitro, in vivo and in humans. Also, the immune response depends on arabinoxylans structure, the degree of branching and origin.

Originality/value

This review paper focuses on the effects of arabinoxylans from rice bran and wheat on immunomodulatory potentials in vitro, in vivo and in humans. A new mechanism of action has been proposed based on the literature and via linking between arabinoxylans and lipopolysaccharide structure, molecular weight and suggested proposed receptor, which might be activated via both of them.

Contribution of Polyphenol Oxidation, Chlorophyll and Vitamin C Degradation to the Blackening of Piper nigrum L

Black pepper (Piper nigrum L.) is the most widely used spice in the world. Blackening is considered to be beneficial and important in the processing of black pepper because it contributes to its color and flavor. The purpose of this paper is to investigate polyphenol oxidation as well as the chlorophyll and vitamin C (VC) degradation in the blackening of Piper nigrum L. Black pepper was produced by four methods, and changes in polyphenols, chlorophyll and VC were studied by high performance liquid chromatography (HPLC) and ultraviolet-visible and visible (UV-Vis) spectrophotometry. The results show that polyphenol oxidase activity significantly decreased during the preparation of black pepper, and the concentrations of phenolic compounds, VC, and chlorophyll a and b also significantly decreased. Polyphenol oxidation and chlorophyll and VC degradation contribute to the blackening. A crude extract of phenolic compounds from black pepper was prepared by the system solvent method. The greater the polarity of the extraction solvent, the higher the extraction rates of the phenolic compounds and the total phenol content. Pepper phenolic compounds were analyzed by HPLC analysis.

Changes in phenolic acid composition and associated enzyme activity in shoot and kernel fractions of brown rice during germination

Phenolic acid composition and activities of two associated enzymes such as PAL (phenylalanine ammonia-lyase) and CW-PRX (cell wall peroxidase) in brown rice (BR) were examined during a germination for 4 days. Shoot and kernel fractions of the germinated brown rice were separated, and soluble extracts and insoluble residues of the fractions were analyzed. In the shoot fraction, the PAL activity and soluble phenolic acid content reached to its maximum on the second day of atmospheric germination, and decreased thereafter. In contrast, the amount of insoluble phenolic acids and CW-PRX activity continuously increased during the germination for 4 days. Comparing the shoot fractions, the kernel fraction exhibited lower activities of PAL and CW-PRX, but showed an increase in total phenolic acid content during germination. Germination raised the antioxidant activity of brown rice, especially in the shoot fraction which contained more phenolic acids than the kernel fraction.

Intestinal Permeability and Cellular Antioxidant Activity of Phenolic Compounds from Mango (Mangifera indica cv. Ataulfo) Peels

Mango (Mangifera indica cv. Ataulfo) peel contains bound phenolics that may be released by alkaline or acid hydrolysis and may be converted into less complex molecules. Free phenolics from mango cv. Ataulfo peel were obtained using a methanolic extraction, and their cellular antioxidant activity (CAA) and permeability were compared to those obtained for bound phenolics released by alkaline or acid hydrolysis. Gallic acid was found as a simple phenolic acid after alkaline hydrolysis along with mangiferin isomers and quercetin as aglycone and glycosides. Only gallic acid, ethyl gallate, mangiferin, and quercetin were identified in the acid fraction. The acid and alkaline fractions showed the highest CAA (60.5% and 51.5%) when tested at 125 µg/mL. The value of the apparent permeability coefficient (Papp) across the Caco-2/HT-29 monolayer of gallic acid from the alkaline fraction was higher (2.61 × 10⁻⁶ cm/s) than in the other fractions and similar to that obtained when tested pure (2.48 × 10⁻⁶ cm/s). In conclusion, mango peels contain bound phenolic compounds that, after their release, have permeability similar to pure compounds and exert an important CAA. This finding can be applied in the development of nutraceuticals using this important by-product from the mango processing industry.

In vitro bioaccessibility, transepithelial transport and antioxidant activity of Urtica dioica L. phenolic compounds in nettle based food products

Nettle (Urtica dioica L.) is a well-known plant with a wide historical background use of stems, roots and leaves. Nettle leaves are an excellent source of phenolic compounds, principally 3-caffeoylquinic acid (3-CQA), caffeoylmalic acid (CMA) and rutin. The aim of this work was to evaluate the bioaccessibility (BAC), the bioavailability (BAV) and the antioxidant activity of nettle phenolic compounds present in foods and supplements. The BAC of nettle phenolics was evaluated with an in vitro dynamic digestion of real food matrices: the type of food matrix and chemical characteristic affected the kinetics of release and solubilization, with the highest BAC after duodenal digestion. A study of duodenal trans epithelial transport evidenced low bioavailability of native forms of 3-CQA, CMA and rutin. Simulation of colonic metabolism confirmed that phenolic compounds are fermented by gut microflora, confirming the need for further investigations on the impact of phenolic compounds at the large intestine level. Photochemiluminescence assay of the simulated digestion fluids demonstrated that ingestion of Urtica based foods contributes to create an antioxidant environment against superoxide anion radicals in the entire gastrointestinal tract (GIT).

Fast spectroscopic monitoring of inhibitors in the 2G ethanol process

One of the main challenges of second generation (2G) ethanol production is the high quantities of phenolic compounds and furan derivatives generated in the pretreatment of the lignocellulosic biomass, which inhibit the enzymatic hydrolysis and fermentation steps. Fast monitoring of these inhibitory compounds could provide better control of the pretreatment, hydrolysis, and fermentation processes by enabling the implementation of strategic process control actions. We investigated the feasibility of monitoring these inhibitory compounds by ultraviolet-visible (UV-Vis) spectroscopy associated with partial least squares (PLS) regression. Hydroxymethylfurfural, furfural, vanillin, and ferulic and p-coumaric acids generated during different severities of liquid hot water pretreatment of sugarcane bagasse were quantified with highly accuracy. In cross-validation (leave-one-out), the PLS-UV-Vis method presented root mean square error of prediction (RMSECV) of around only 5.0%. The results demonstrated that the monitoring performance achieved with PLS-UV-Vis could support future studies of optimization and control protocols for application in industrial processes.

Superfruits: Phytochemicals, antioxidant efficacies, and health effects - A comprehensive review

The term "superfruit" has gained increasing usage and attention recently with the marketing strategy to promote the extraordinary health benefits of some exotic fruits, which may not have worldwide popularity. This has led to many studies with the identification and quantification of various groups of phytochemicals. This contribution discusses phytochemical compositions, antioxidant efficacies, and potential health benefits of the main superfruits such as açai, acerola, camu-camu, goji berry, jaboticaba, jambolão, maqui, noni, and pitanga. Novel product formulations, safety aspects, and future perspectives of these superfruits have also been covered. Research findings from the existing literature published within the last 10 years have been compiled and summarized. These superfruits having numerous phytochemicals (phenolic acids, flavonoids, proanthocyanidins, iridoids, coumarins, hydrolysable tannins, carotenoids, and anthocyanins) together with their corresponding antioxidant activities, have increasingly been utilized. Hence, these superfruits can be considered as a valuable source of functional foods due to the phytochemical compositions and their corresponding antioxidant activities. The phytochemicals from superfruits are bioaccessible and bioavailable in humans with promising health benefits. More well-designed human explorative studies are needed to validate the health benefits of these superfruits.

A Comparison of the Chemical Composition, In Vitro Bioaccessibility and Antioxidant Activity of Phenolic Compounds from Rice Bran and Its Dietary Fibres

The composition, in vitro bioaccessibility and antioxidant activities of the phenolic compounds in defatted rice bran (DRB) and its soluble and insoluble dietary fibres were systematically evaluated in this study. The total phenolic content of insoluble dietary fibre from DRB (IDFDRB) was much higher than that of the soluble dietary fibre from DRB (SDFDRB) but was 10% lower than that of DRB. Bound phenolics accounted for more than 90% of the total phenolics in IDFDRB, whereas they accounted for 34.2% and 40.5% of the total phenolics in DRB and SDFDRB, respectively. Additionally, the phenolic profiles and antioxidant activities were significantly different in DRB, SDFDRB and IDFDRB. The phenolic compounds in IDFDRB were much less bioaccessibility than those in DRB and SDFDRB due to the higher proportion of bound phenolics in IDFDRB. Considering that bound phenolics could be released from food matrices by bacterial enzymes in the large intestine and go on to exert significant beneficial health effects in vivo, further studies on IDFDRB are needed to investigate the release of the phenolics from IDFDRB via gut microbiota and the related health benefits.

pH-controlled fermentation in mild alkaline conditions enhances bioactive compounds and functional features of lentil to ameliorate metabolic disturbances

Lentil fermentation has a promising potential as a strategy for development of multifunctional ingredients targeting metabolic syndrome (MetS). Response surface methodology was applied to optimize lentil fermentation and study its effects on generation of peptides, soluble phenolics and bioactivities. Fermentation using Lactobacillus plantarum and Savinase® 16 L was carried out at different pH (6.5-8.5) and times (5.5-30 h). Analysis of variance was performed to evaluate linear, quadratic and interaction effects between fermentation parameters. pH positively affected peptides, soluble phenolic compounds and antioxidant activity whereas a negative impact on lipase inhibitory activity was observed (p < .0001). Time showed positive effect on proteolysis and negatively affected angiotensin I-converting enzyme inhibitory activity of fermented lentil (p < .0001). Multivariate optimization led to high levels of peptides, soluble phenolics and bioactivity of fermented lentil at pH 8.5 and 11.6 h. In conclusion, this study might contribute to the development of functional ingredients from lentil for MetS management.

Optimal germination condition impacts on the antioxidant activity and phenolic acids profile in pigmented desi chickpea (Cicer arietinum L.) seeds

Legume sprouts are considered natural, healthy products that provide a source of bioactive compounds to fight against chronic diseases. This study aims to identify the optimal germination temperature (GT) and germination time (Gt) to maximize total phenolic and flavonoid contents (TPC, FC), and antioxidant activity (AoxA) of desi chickpea. Response surface methodology was used as an optimization tool. An experimental design with two factors (GT and Gt) and five levels was used (13 treatments). The sprouts from each treatment were lyophilized, tempered, and milled to obtain germinated chickpea flours (GCF). To predict the phytochemicals composition and AoxA in GCF, regression models were developed. Maximum TPC, FC, and AoxA were attained during germination 33.7 °C for 171 h. Optimized germinated chickpea flour produced applying the optimal germination conditions resulted in an increase of protein and total dietary fibre content, TPC, FC, phenolic acids profile, and AoxA. Germination at optimal conditions also increased the level of coumaric, ferulic, synapic, ellagic, and syringic acids. This study demonstrated that germination carried out under optimal conditions enhanced the nutraceutical value of desi chickpea seeds.

Health-related effects and improving extractability of cereal arabinoxylans

Arabinoxylans (AXs) are major dietary fibers. They are composed of backbone chains of β-(1-4)-linked xylose residues to which α-l-arabinose are linked in the second and/or third carbon positions. Recently, AXs have attracted a great deal of attention because of their biological activities such as their immunomodulatory potential. Extraction of AXs has some difficulties; therefore, various methods have been used to increase the extractability of AXs with varying degrees of success, such as alkaline, enzymatic, mechanical extraction. However, some of these treatments have been reported to be either expensive, such as enzymatic treatments, or produce hazardous wastes and are non-environmentally friendly, such as alkaline treatments. On the other hand, mechanical assisted extraction, especially extrusion cooking, is an innovative pre-treatment that has been used to increase the solubility of AXs. The aim of the current review article is to point out the health-related effects and to discuss the current research on the extraction methods of AXs.

Gut Fermentation of Dietary Fibres: Physico-Chemistry of Plant Cell Walls and Implications for Health

The majority of dietary fibre (DF) originates from plant cell walls. Chemically, DF mostly comprise carbohydrate polymers, which resist hydrolysis by digestive enzymes in the mammalian small intestine, but can be fermented by large intestinal bacteria. One of the main benefits of DF relate to its fermentability, which affects microbial diversity and function within the gastro-intestinal tract (GIT), as well as the by-products of the fermentation process. Much work examining DF tends to focus on various purified ingredients, which have been extracted from plants. Increasingly, the validity of this is being questioned in terms of human nutrition, as there is evidence to suggest that it is the actual complexity of DF which affects the complexity of the GIT microbiota. Here, we review the literature comparing results of fermentation of purified DF substrates, with whole plant foods. There are strong indications that the more complex and varied the diet (and its ingredients), the more complex and varied the GIT microbiota is likely to be. Therefore, it is proposed that as the DF fermentability resulting from this complex microbial population has such profound effects on human health in relation to diet, it would be appropriate to include DF fermentability in its characterization-a functional approach of immediate relevance to nutrition.

Enzymatic action mechanism of phenolic mobilization in oats (Avena sativa L.) during solid-state fermentation with Monascus anka

This work aims to investigate the effects of carbohydrate-hydrolysing enzymes on the release of phenolics in oat fermentation with Monascus anka. There were good correlations between phenolic content and α-amylase, xylanase and FPase activities. A high level of α-amylase activity (141.07 U/g) was observed, while xylanase (2.40 U/g), total cellulase (0.52 U/g) and β-glucosidase activities (0.028 U/g) were relatively low in the fermentation system. The phenolic content of oat powder treated with crude enzyme from fermented oats significantly increased, especially that of the ferulic acid in the insoluble fraction and the vanillic acid in the soluble fraction. The surface SEM morphology of the oats showed that the cell wall structure was damaged by the crude enzyme treatment, which led to the release of phenolics. This study could provide metabolic understanding for optimization of phenolic compounds which could more efficiently increase the nutrition of oat intended for functional food ingredients.

Contribution and Interactions of Hydroxycinnamic Acids Found in Bran and Wholegrain Sorghum (Sorghum bicolor L. Moench): Effects on the Antioxidant Capacity and Inhibition of Human Erythrocyte Hemolysis

An imbalance between free radicals and antioxidants is known as oxidative stress, and it promotes cellular aging and the development of chronic noncommunicable diseases. The bioactive compounds present in food play an important role in preventing oxidative stress. The aim of this study was to determine the contributions and interactions of the hydroxycinnamic acids found in the bran and whole grain of sorghum and to evaluate their effects on the antioxidant capacity and inhibition of the hemolysis of human erythrocytes. Results showed that the caffeic acid, p-coumaric acid, and ferulic acid found in sorghum contributed to the scavenging of DPPH and ABTS radicals in various proportions. Ferulic acid, which was present in bound form in the bran and wholegrain sorghum, significantly inhibited the AAPH radical-induced oxidation of the erythrocyte membranes by 78.0 and 4.3%, respectively. Combinations of two, three, or four hydroxycinnamic acids may interact in an antagonistic or synergistic manner, thereby altering each other's bioactivities. The various interactions between the different sorghum bioactives can have a significant impact on their potential bioactivities. These results can be useful in the design of functional foods that aim to deliver bioactives to mitigate cellular aging or noncommunicable diseases.

Cooking quality properties and free and bound phenolics content of brown, black, and red rice grains stored at different temperatures for six months

The changes in cooking quality and phenolic composition of whole black and red rice grains stored during six months at different temperatures were evaluated. Brown rice with known cooking quality properties and low phenolic levels was used for purposes comparison. All rice genotypes were stored at 13% moisture content at temperatures of 16, 24, 32, and 40°C. Cooking time, hardness, free and bound phenolics, anthocyanins, proanthocyanidins, and free radical scavenging capacity were analysed. The traditional rice with brown pericarp exhibited an increase in cooking time and free phenolics content, while rice with black pericarp exhibited a reduction in cooking time after six months of storage at the highest studied temperature of 40°C. There as increases in ferulic acid levels occurred as a function of storage temperature. Red pericarp rice grains showed decreased antioxidant capacity against ABTS radical for the soluble phenolic fraction with increased time and storage temperature.

Phytochemical composition and β-glucan content of barley genotypes from two different geographic origins for human health food production

In the present study, 27 barley genotypes (Hordeum vulgare L.) grown in two geographic origins (Czech Republic and Spain) were analysed for their contents of β-glucan, tocols and phenolic compounds (free and bound). The samples included hulled, hull-less and coloured genotypes. The results showed that concentrations of β-glucan range from 2.40 to 7.42g/100g. Total tocol content of the barley samples ranged between 39.9 and 81.6μg/g. A total of 64 compounds were identified in the barley samples. These included 19 phenolic acids and aldehydes, 9 flavan 3-ols, 9 flavone glycosides, and 27 anthocyanins. The results showed a wide range of phenolic concentrations in the barley samples, highlighting the presence of considerable amounts of anthocyanins in purple barley genotypes. In synthesis, barley should be considered a good source of bioactive components, especially because of the broad spectrum of phytochemicals with potential health benefits besides the soluble fibre (β-glucan).

Germination under Moderate Salinity Increases Phenolic Content and Antioxidant Activity in Rapeseed (Brassica napus var oleifera Del.) Sprouts

The use of sprouts in the human diet is becoming more and more widespread because they are tasty and high in bioactive compounds and antioxidants, with related health benefits. In this work, we sprouted rapeseed under increasing salinity to investigate the effect on free and bound total phenolics (TP), non-flavonoids (NF), tannins (TAN), phenolic acids (PAs), and antioxidant activity. Seeds were incubated at 0, 25, 50, 100, 200 mM NaCl until early or late sprout stage, i.e., before or after cotyledon expansion, respectively. Sprouting and increasing salinity slightly decreased the bound fractions of TP, NF, TAN, PAs, while it increased markedly the free ones and their antioxidant activity. Further increases were observed in late sprouts. Moderate salinity (25–50 mM NaCl) caused the highest relative increase in phenolic concentration while it slightly affected sprout growth. On the contrary, at higher NaCl concentrations, sprouts grew slowly (100 mM NaCl) or even died before reaching the late sprout stage (200 mM). Overall, moderate salinity was the best compromise to increase phenolic content of rapeseed sprouts. The technique may be evaluated for transfer to other species as a cheap and feasible way to increase the nutritional value of sprouts.

Application of Moldavian dragonhead (Dracocephalum moldavica L.) leaves addition as a functional component of nutritionally valuable corn snacks

Application of Moldavian dragonhead (Dracocephalum moldavica L.) leaves in extruded snacks was evaluated. Directly expanded corn snacks (crisps) were supplemented with 5-20% of dragonhead leaves. The supplemented snacks were characterized to have improved nutritional value and were a good source of dietary fibre. The presence of phenolic compounds, especially rosmarinic acid, showed a high antioxidant potential and a radical scavenging activity of tested snacks, especially if a high content of additive was used. The increasing amount of additive also had an impact on the physical properties of extrudates lowering the expansion ratio, water absorption and solubility, yet increasing bulk density, cutting force and the breaking index of the enriched snacks. The highest viscosity was observed at 5 and 10% addition level. The increasing amount of dragonhead leaves lowered the brightness of snacks and increased the greenness tint significantly. A sensory evaluation showed good acceptability of snacks enriched with up to 15% of dragonhead dried leaves. Dried leaves of the Moldavian dragonhead seem to be a prospective functional additive for extruded crisps with a high nutritional value, especially because of dietary fibre and rosmarinic acid content, a strong antioxidant potential and acceptable sensory properties.

Strategies for the extraction and analysis of non-extractable polyphenols from plants

The majority of studies based on phenolic compounds from plants are focused on the extractable fraction derived from an aqueous or aqueous-organic extraction. However, an important fraction of polyphenols is ignored due to the fact that they remain retained in the residue of extraction. They are the so-called non-extractable polyphenols (NEPs) which are high molecular weight polymeric polyphenols or individual low molecular weight phenolics associated to macromolecules. The scarce information available about NEPs shows that these compounds possess interesting biological activities. That is why the interest about the study of these compounds has been increasing in the last years. Furthermore, the extraction and characterization of NEPs are considered a challenge because the developed analytical methodologies present some limitations. Thus, the present literature review summarizes current knowledge of NEPs and the different methodologies for the extraction of these compounds, with a particular focus on hydrolysis treatments. Besides, this review provides information on the most recent developments in the purification, separation, identification and quantification of NEPs from plants.

Cytotoxic and Immunomodulatory Potential Activity of Physalis peruviana Fruit Extracts on Cervical Cancer (HeLa) and Fibroblast (L929) Cells

It was purposed to evaluate the biological potential of ethanol and isopropanol crude extracts of ripe Physalis peruviana fruits. Cytotoxic and immunomodulatory effects of the expression of interleukin-6, interleukin-8, and monocyte chemoattractant protein-1 (MCP-1) were evaluated on human cervical cancer (HeLa) and murine fibroblast (L929) cells. The composition was evaluated by high-performance liquid chromatography diode-array detection and high-performance liquid chromatography ultraviolet/visible detection. The presence of ursolic acid and rosmarinic acid was found in both solvents. However, gallic acid, quercetin, and epicatechin were higher in isopropanol extracts (P < .05). The results indicated a relationship among the total polyphenol content, antioxidant activity, and cytotoxic activity that was dependent on the solvent used. Isopropanol extracts presented a half-maximal inhibition concentration value (IC₅₀) of 60.48 ± 3.8 μg/mL for HeLa cells and 66.62 ± 2.67 μg/mL for L929 fibroblasts. The extracts reduced the release of interleukin-6, interleukin-8, and MCP-1 in a dose-dependent manner. Extracts showed anticancer and immunomodulatory potential for new complementary pharmaceutical products development.

Evaluation of polyphenolic content and antioxidant activity in two onion varieties grown under organic and conventional production systems

BACKGROUND

Onions contain a number of bioactive compounds, in particular polyphenols. They are rich sources of such compounds in the human diet and offer significant health benefits to the consumer. Demand for organic crops is steadily increasing partly based on the expected health benefits of organic food consumption. The current study examines the influence of organic and conventional crop management practices on bioactive polyphenolic content of onion.

RESULTS

We examined the effect of conventional, organic, and mixed cultivation practices on the content of total phenolics, total flavonoids and antioxidant activity in two varieties of onion grown over 4 years in a split-plot factorial systems comparison trial. Levels of total phenolics and total flavonoids showed a significant year-on-year variation and were significantly different between organic and conventional production systems. The levels of total phenolics, total flavonoids and antioxidant activity in general were significantly higher (P < 0.05) under fully organic compared to fully conventional management.

CONCLUSION

Organic cultivation practices resulted in significantly higher levels of potential bioactive compounds in onion. © 2016 Society of Chemical Industry.

Analysis of polyphenols in brewer's spent grain and its comparison with corn silage and cereal brans commonly used for animal nutrition

Brewer's spent grain (BSG) could be tested as an alternative source of polyphenols in animal nutrition. Proper extraction and analytical methods are critical for quantification. Thus, extraction for BSG, corn silage, and brans of rice, corn, and wheat were studied for the highest yield of polyphenols. A method for 18 phenolic monomers by HPLC-DAD was developed, validated, and applied to samples. An aqueous solution of NaOH (0.75% w/v) using integral samples for extraction resulted in the highest values for colorimetric measurements in all analyzed sources. Method by maceration showed the highest phenolic yield when applied in corn silage and BSG. However, for brans the best method was microwave assisted. Results from HPLC-DAD analysis clearly showed that native structures of phenolic compounds were simplified to its monomers allowing quantification and sample discrimination. BSG had the highest concentration of polyphenols and could be a promising and innovative source for animal feed studies.

Influence of fruit juice processing on anthocyanin stability

Anthocyanins are quality determining compounds in red fruits and their corresponding juices. The fate of anthocyanins during production of juices is determined by countless factors and all of these need to be taken into consideration to optimize juice processes. Storage and pre-press procedures like freezing and thawing may influence the fruit's integrity and accordingly affects the extraction of valuable components during the subsequent mashing and pressing. Conventional thermal or novel non-thermal treatments to ensure microbial safety have both positive and negative effects on the anthocyanins. By inactivation of oxidizing enzymes, profiles and quantities of anthocyanins may be maintained, but more severe conditions may have adverse effects. To improve juice extraction and to increase yield, enzyme-assisted degradation of the cell walls is conducted. The applied enzyme preparations contain numerous side activities which also may degrade anthocyanins. Clarification and concentration will further reduce the final anthocyanin concentrations. Many studies have been published regarding evaluating individual fruits or single processing steps but, obviously, these results are not necessarily transferable. Accordingly, this review aims to summarize all relating studies comprehensively to the fate of anthocyanins during juice processing giving an overview of underlying mechanisms as well as the chemical and analytical background.

Evolution of the antioxidant capacity and phenolic contents of persimmon during fermentation

The changes in antioxidant capacity and phenolics of persimmon during alcoholic fermentation, acetification, and short aging were investigated. An increase in the antioxidant activity was observed when persimmon was transformed from puree to vinegar. The total content of phenolics remained stable, in contrast to the concentration of condensed tannin, which significantly (p < 0.05) increased during alcoholic and acetic fermentations, although followed by a decrease after aging. The phenolic compounds were characterized and quantitated. Gallic acid was the main phenolic compound, and its content increased by 14.4% during alcoholic fermentation and reduced by 53.5% during acetic fermentation. Additionally, the flavan-3-ol compounds increased during alcoholic fermentation and acetification. Vanillyl alcohol, (-)-epigallocatechin, and p-coumaric acid were not observed in persimmon puree but detected in persimmon wine and vinegar. These results indicate that alcoholic and acetic fermentation can improve the antioxidant capacity of persimmon fruit.