The potential of priming in food production

Tomato Processing By-Products Valorisation through Ohmic Heating Approach

Tomato by-products from processing industries have a higher potential to be reused as a source of bioactive compounds. Reliable national data on tomato by-products and physicochemical characterisation that will inform and find effective planning on tomato waste management in Portugal is absent. To help obtain this knowledge, selected Portugal companies were recruited to obtain representative samples of by-products generation, and physicochemical composition was evaluated. Furthermore, an environmental-friendly method (the ohmic heating (OH) method, which allows the recovery of bioactive compounds in absence of hazardous reagents) was also used and compared with conventional methods to explore new safe value-added ingredients. Total antioxidant capacity and total and individual phenolic compounds were also evaluated by spectrophotometric and high-performance liquid chromatography (HPLC), respectively. Tomato processing by-products have revealed a higher potential since both collected samples from companies were rich in protein (between 16.3 to 19.4 g/100 g DW, with fibre content ranging from 57.8 to 59.0 g/100 g DW). In addition, these samples contain 17.0 g/100 g of fatty acids (mainly polyunsaturated, monounsaturated and saturated, such as linoleic, oleic, and palmitic acid, respectively). Also, they present mainly chlorogenic acid and rutin as phenolic compounds. After understanding its composition, the OH was applied to determine added-value solutions to tomato by-products. With extractions, two types of fractions were obtained, namely liquid fraction rich in phenols, free sugars, and carotenoids and a solid fraction rich in fibre bound to phenols and carotenoids. This treatment has been shown to have the ability to preserve carotenoids, such as lycopene relative to conventional methods. Nevertheless, new molecules were identified by LC-ESI-UHR-OqTOF-MS analysis, such as phene-di-hexane and N-acethyl-D-tryptophan. According to the results, the OH boosts the potential of tomato by-products and can be directly introduced into the process, contributing to the circular economy and zero by-products.

Resveratrol alleviates pyraclostrobin-induced lipid peroxidation, oxidative stress, and DNA damage in rats

Pyraclostrobin (Pyra) is a fungicide in the strobilurin class and has proven to be very toxic to organisms primarily aquatic species. Resveratrol (Res) is a phytoalexin that exhibits multiple bioactivities as anti-oxidative, anti-inflammatory, cardiovascular protective, and anti-aging and is found in plant species such as mulberry, peanut, and grape. This study aimed to determine the protective effect of Res against Pyra-induced lipid peroxidation, oxidative stress, and DNA damage in rats. For this purpose, a total of 48 male rats divided into 6 groups - 8 in each group - were exposed to 30 mg/kg Pyra by oral gavage once a day for 30 days and to three different concentrations of Res (5, 10, and 20 mg/kg) together with Pyra. Pyra administration increased liver enzyme parameters and malondialdehyde (MDA) levels whereas decreased glutathione (GSH) levels and activities of superoxide dismutase (SOD) and catalase (CAT). Also, Pyra treatment increased pro-apoptotic (Bax), apoptotic (Caspase-3, Caspase-8, and Caspase-9), pro-inflammatory (NFκB), cancer (CYP2E1), and cell regulatory (p53) gene expressions and decreased anti-apoptotic (Bcl-2) gene expression in the liver. Furthermore, DNA damage in blood and histopathological changes in the liver and kidney were observed with Pyra administration. In contrast, Res administrations in a dose-dependent manner improved Pyra-induced lipid peroxidation, oxidative and DNA damages, expression levels of these genes in the liver, and histopathological changes in the liver and kidney. Consequently, the treatment of Res, known for its anti-oxidant and protective properties, exhibited a protective effect on Pyra-induced lipid peroxidation, oxidant/anti-oxidant status, gene expressions, and DNA damage in rats.

Effects Induced by the Agricultural Application of Probiotics on Antioxidant Potential of Strawberries

With the recent rapid development of the functional food sector, agriculture is looking for alternatives to improve the quality of food grown by limiting chemical fertilizers. This study evaluated the effects of two commercial plant probiotics, ProbioHumus and NaturGel, on the growth and quality of strawberry fruits. Strawberry plants were sprayed with microbial probiotics twice a year: after harvesting at the beginning of dormancy and at the stage of leaf development. Spray applications of ProbioHumus, NaturGel, and NaturGel + ProbioHumus in the organic farm fields significantly increased the fresh fruit weight up to 42%, 35%, and 37%, respectively, compared to the non-treated control. An increase in the weight of fresh strawberry fruits may be associated with an increase in dry matter accumulation. The probiotics had a positive effect on the total content of phenols, anthocyanins, and especially ascorbic acid in strawberry fruits. The increase in ascorbic acid in strawberry fruits was up to 97% compared to the non-treated control. The fruits from plants inoculated with probiotics showed significantly higher antioxidant activity. In summary, ProbioHumus and NaturGel are effective tools for improving the quality of strawberries and can be exploited in sustainable agriculture as a tool for adding value to functional food.

Metabolic elicitors of Pseudomonas fluorescens N 21.4 elicit flavonoid metabolism in blackberry fruit

BACKGROUND

The beneficial rhizobacterium, Pseudomonas fluorescens N 21.4, and its metabolic elicitors were inoculated in commercial cultivars of blackberry plants (Rubus cv. Loch Ness). Phenolic compounds present in red and black fruit and the expression of structural marker genes of the phenylpropanoid pathway during fruit ripening were studied.

RESULTS

An inverse relationship between gene expression and accumulation of metabolites was seen, except for the RuDFR gene, which had a direct correlation with cyanidin 3-O-glucoside synthesis, increasing its content 1.3 times when RuDFR was overexpressed in the red fruit of plants inoculated with the metabolic elicitors of P. fluorescens N 21.4, compared with red fruit of plants inoculated with N 21.4. The RuCHS gene also had a fundamental role in the accumulation of metabolites. Both rhizobacterium and metabolic elicitors triggered the flavonoid metabolism, enhancing the catechin and epicatechin content between 1.1 and 1.6 times in the case of red fruit and between 1.1 and 1.8 times in the case of black fruit. Both treatments also boosted the anthocyanin, quercetin, and kaempferol derivative content, highlighting the effects of metabolic elicitors in red fruit and the effects of live rhizobacterium in black fruit.

CONCLUSION

The metabolic elicitors' capacity to modulate gene expression and to increase secondary metabolites content was demonstrated. This work therefore suggests that they are effective, affordable, easily manageable, and ecofriendly plant inoculants that complement, or are alternatives to, beneficial rhizobacteria. © 2020 Society of Chemical Industry.

Effect of arachidonic and jasmonic acid elicitation on the content of phenolic compounds and antioxidant and anti-inflammatory properties of wheatgrass (Triticum aestivum L.)

The effect of elicitation with arachidonic and jasmonic acids on the production of phenolic compounds as well as the antioxidant and anti-inflammatory properties of phenolic extracts of wheatgrass was evaluated. The qualitative and quantitative analysis of phenolic compounds carried out with the UPLC-MS technique indicated that luteolin and apigenin derivatives were the dominant flavonoids, while ferulic acid derivatives and syringic acid were the main components in the phenolic acid fraction in the wheatgrass. No qualitative changes in the examined phenolic compounds were observed in the case of the control and elicited plants, while there was an increase in the content of some compounds. The antioxidant activity increased in the elicited samples (with the exception of reducing power) and this elevation was partially correlated with the increase in the polyphenol content in the studied plants. Elicitation with 0.01 µM arachidonic acid also caused improvement of potential anti-inflammatory properties of the wheatgrass.

Exogenous nitric oxide induces disease resistance against Monilinia fructicola through activating the phenylpropanoid pathway in peach fruit

BACKGROUND

Nitric oxide (NO) is a multifunctional signaling molecule involved in plant-induced resistance to disease. The present study aimed to investigate the relationship between disease resistance induced by NO and the phenylpropanoid pathway in peach fruit. The present study investigated the effect of NO on the main enzymes and metabolites of the phenylpropanoid pathway of harvested peach, which are probably related to disease resistance against Monilinia fructicola.

RESULTS

The results showed that treatment with 15 µmol L^-1 NO significantly (P < 0.05) enhanced the activities of phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumaroyl-CoA ligase, chalcone synthase and chalcone isomerase and the expression of their genes. Furthermore, NO treatment significantly (P < 0.05) increased the contents of total phenolics, flavonoids and lignin over the entire storage period and maintained higher total anthocyanin, phenolic acid and anthocyanin contents during the earlier storage period.

CONCLUSION

These results suggest that NO treatment could activate the phenylpropanoid pathway to enhance the activity of related enzymes and the contents of phenylpropanoid metabolites in peach to improve disease resistance and prevent pathogenic invasion. © 2016 Society of Chemical Industry.

Application of Pseudomonas fluorescens to Blackberry under Field Conditions Improves Fruit Quality by Modifying Flavonoid Metabolism

Application of a plant growth promoting rhizobacterium (PGPR), Pseudomonas fluorescens N21.4, to roots of blackberries (Rubus sp.) is part of an optimised cultivation practice to improve yields and quality of fruit throughout the year in this important fruit crop. Blackberries are especially rich in flavonoids and therefore offer potential benefits for human health in prevention or amelioration of chronic diseases. However, the phenylpropanoid pathway and its regulation during ripening have not been studied in detail, in this species. PGPR may trigger flavonoid biosynthesis as part of an induced systemic response (ISR) given the important role of this pathway in plant defence, to cause increased levels of flavonoids in the fruit. We have identified structural genes encoding enzymes of the phenylpropanoid and flavonoid biosynthetic pathways catalysing the conversion of phenylalanine to the final products including flavonols, anthocyanins and catechins from blackberry, and regulatory genes likely involved in controlling the activity of pathway branches. We have also measured the major flavonols, anthocyanins and catechins at three stages during ripening. Our results demonstrate the coordinated expression of flavonoid biosynthetic genes with the accumulation of anthocyanins, catechins, and flavonols in developing fruits of blackberry. Elicitation of blackberry plants by treatment of roots with P.fluorescens N21.4, caused increased expression of some flavonoid biosynthetic genes and an accompanying increase in the concentration of selected flavonoids in fruits. Our data demonstrate the physiological mechanisms involved in the improvement of fruit quality by PGPR under field conditions, and highlight some of the genetic targets of elicitation by beneficial bacteria.

The role of isoflavone metabolism in plant protection depends on the rhizobacterial MAMP that triggers systemic resistance against Xanthomonas axonopodis pv. glycines in Glycine max (L.) Merr. cv. Osumi

Glycine max (L.) Merr. plays a crucial role in both the field of food and the pharmaceutical industry due to their input as plant protein and to the benefits of isoflavones (IF) for health. In addition, IF play a key role in nodulation and plant defense and therefore, an increase in IF would be desirable for better field performance. IF are secondary metabolites and therefore, inducible, so finding effective agents to increase IF contents is interesting. Among these agents, plant growth promoting rhizobacteria (PGPR) have been used to trigger systemic induction of plant's secondary metabolism through their microbe associated molecular patterns (MAMPs) that fit in the plant's receptors to start a systemic response. The aim of this study was to evaluate the ability of 4 PGPR that had a contrasted effect on IF metabolism, to protect plants against biotic stress and to establish the relation between IF profile and the systemic response triggered by the bacteria. Apparently, the response involves a lower sensitivity to ethylene and despite the decrease in effective photosynthesis, growth is only compromised in the case of M84, the most effective in protection. All strains protected soybean against Xanthomonas axonopodis pv. glycines (M84 > N5.18 > Aur9>N21.4) and only M84 and N5.18 involved IF. N5.18 stimulated accumulation of IF before pathogen challenge. M84 caused a significant increase on IF only after pathogen challenge and N21.4 caused a significant increase on IF content irrespective of pathogen challenge. Aur9 did not affect IF. These results point out that all 4 strains have MAMPs that trigger defensive metabolism in soybean. Protection induced by N21.4 and Aur9 involves other metabolites different to IF and the role of IF in defence depends on the previous metabolic status of the plant and on the bacterial MAMP.

Water shortage and quality of fleshy fruits--making the most of the unavoidable

Extreme climatic events, including drought, are predicted to increase in intensity, frequency, and geographic extent as a consequence of global climate change. In general, to grow crops successfully in the future, growers will need to adapt to less available water and to take better advantage of the positive effects of drought. Fortunately, there are positive effects associated with drought. Drought stimulates the secondary metabolism, thereby potentially increasing plant defences and the concentrations of compounds involved in plant quality, particularly taste and health benefits. The role of drought on the production of secondary metabolites is of paramount importance for fruit crops. However, to manage crops effectively under conditions of limited water supply, for example by applying deficit irrigation, growers must consider not only the impact of drought on productivity but also on how plants manage the primary and secondary metabolisms. This question is obviously complex because during water deficit, trade-offs among productivity, defence, and quality depend upon the intensity, duration, and repetition of events of water deficit. The stage of plant development during the period of water deficit is also crucial, as are the effects of other stressors. In addition, growers must rely on relevant indicators of water status, i.e. parameters involved in the relevant metabolic processes, including those affecting quality. Although many reports on the effects of drought on plant function and crop productivity have been published, these issues have not been reviewed thus far. Here, we provide an up-to-date review of current knowledge of the effects of different forms of drought on fruit quality relative to the primary and secondary metabolisms and their interactions. We also review conventional and less conventional indicators of water status that could be used for monitoring purposes, such as volatile compounds. We focus on fruit crops owing to the importance of secondary metabolism in fruit quality and the importance of fruits in the human diet. The issue of defence is also briefly discussed.

Annual changes in bioactive contents and production in field-grown blackberry after inoculation with Pseudomonas fluorescens

The aim of this study was two-fold: first, to characterize blackberry fruits from Rubus sp. var. Lochness along the year, and secondly, to evaluate the ability of a Pseudomonas strain (N21.4) to improve fruit yield and quality under field conditions in production greenhouses throughout the year. The strain was root or leaf inoculated to blackberry plants and fruits were harvested in each season. Nutritional parameters, antioxidant potential and bioactive contents were determined; total fruit yield was recorded. Blackberries grown under short day conditions (autumn and winter) showed significantly lower °Brix values than fruits grown under long day conditions. Interestingly, an increase in fruit °Brix, relevant for quality, was detected after bacterial challenge, together with significant and sustained increases in total phenolics and flavonoids. Improvements in inoculated fruits were more evident from October through early March, when environmental conditions are worse. In summary, N21.4 is an effective agent to increase fruit quality and production along the year in blackberry; this is an environmentally friendly approach to increase fruit quality.

Bacterial bioeffectors modify bioactive profile and increase isoflavone content in soybean sprouts (Glycine max var Osumi)

The effect of two bacterial strains to enhance bioactive contents (total phenolic compounds, total flavonoid compounds and isoflavones) and antioxidant activity on 3-day-old soybean sprouts were investigated. To identify bacterial determinants responsible for these effects, viable and UV-treated strains were delivered to wounded seeds at different concentration. Multivariate analysis performed with all the evaluated parameters indicated the different effectiveness of Stenotrophomonas maltophilia N5.18 and Pseudomonas fluorescens N21.4 based on different structural and metabolic determinants for each. N21.4 increased total phenolics and isoflavones from the genistein family, while N5.18 triggered biosynthesis of daidzein and genistein families coupled to a decrease in total phenolics, suggesting different molecular targets in the phenilpropanoid pathway. Only extracts from N5.18 treated seeds showed an improved antioxidant activity according to the β-carotene bleaching prevention method. In summary, bioeffectors from both bacterial strains are effective tools to improve soybean sprouts quality; structural elicitors from N5.18 also enhanced antioxidant activity, being the best alternative for further development of a biotechnological procedure.

Agriculture and bioactives: achieving both crop yield and phytochemicals

Plants are fundamental elements of the human diet, either as direct sources of nutrients or indirectly as feed for animals. During the past few years, the main goal of agriculture has been to increase yield in order to provide the food that is needed by a growing world population. As important as yield, but commonly forgotten in conventional agriculture, is to keep and, if it is possible, to increase the phytochemical content due to their health implications. Nowadays, it is necessary to go beyond this, reconciling yield and phytochemicals that, at first glance, might seem in conflict. This can be accomplished through reviewing food requirements, plant consumption with health implications, and farming methods. The aim of this work is to show how both yield and phytochemicals converge into a new vision of agricultural management in a framework of integrated agricultural practices.

Correlation of rutin accumulation with 3-O-glucosyl transferase and phenylalanine ammonia-lyase activities during the ripening of tomato fruit

In tomato, the predominant flavonoid is quercetin-3-rutinoside (rutin). In this study, we aim to investigate the phenylalanine ammonia-lyase (PAL) and the quercetin-3-O-glucosyl transferase (3-GT) reactions in the formation of rutin during tomato fruit ripening. Tomatoes of the Moneymaker variety at different development stages (green, breaker, turning, pink, red, and deep red) were divided into flesh and peel fractions. In each sample, both the content of rutin and the enzymatic activities for PAL and 3-GT were recorded. The highest activities of PAL were recorded in the peel of turning fruit (3,000 μkat/mg fresh weight). In fruit flesh, maximal activity was observed in red fruit (917.3 μkat/mg). For both tissues, PAL activity strongly decreased at the final (deep red) fruit stage. The activity of 3-GT in peel peaked in the turning fruit stage (50.7 pkat/mg), while in flesh maximal activity (33.4 pkat/mg) was observed in green fruit, which rapidly declined at the turning stage. Higher levels of rutin were detected in the tomato peel compared to the flesh part with the highest level being found at the green stage. The relation of PAL and 3-GT activities to rutin content is also evaluated.

Polyphenols as chemotaxonomic markers in Italian "long-storage" tomato genotypes

"Long-storage" tomato ( Solanum lycopersicum L.) is a niche product typical of the Mediterranean area, traditionally cultivated under no water supply, the fruits of which combine a good taste with excellent nutritional properties. High-performance liquid chromatography coupled with diode array detection and electron spray-mass spectrometry (HPLC/DAD/ESI-MS) was used to identify the phenolic profile in 10 landraces of long-storage tomato, grown under a typical semiarid climate, as compared to a processing tomato hybrid cultivated in the same environment, under both well-irrigated and unirrigated conditions. Sixteen different secondary metabolites, belonging to the classes of cinnamoylquinic acids and flavonoids, were identified. Quantitative analyses were also performed to monitor the changes in the phenolic content along the batch. The results highlighted that landraces originating from the same area exhibit different fruit morphologies but own a similar biochemical profile. Moreover, the two controls (well irrigated and unirrigated) are placed into the same cluster, suggesting that these secondary metabolites in tomato fruits may be more genetics-dependent than environment-dependent. Given the analysis of phenols nowadays represents a useful tool to assess the genetic variability in tomato, these compounds could be adopted as chemotaxonomic markers in the traceability of this niche product.

From vineyard to glass: agrochemicals enhance the melatonin and total polyphenol contents and antiradical activity of red wines

Resistance inducers are a class of agrochemicals, including benzothiadiazole and chitosan, which activate the plant own defence mechanisms. In this work, open-field treatments with plant activators were performed on two red grape (Vitis vinifera L.) varieties cultivated in different localities, Groppello (Brescia, Lombardia, Italy) and Merlot (Treviso, Veneto, Italy). Treatments were carried out every 10 days until the véraison and, after harvesting, experimental wines (microvinificates) were prepared. In general, both melatonin and total polyphenol content, determined by mass spectrometry and Folin-Ciocalteu assay, respectively, were higher in wines produced from grapes treated with resistance inducers than in those obtained from untreated control and conventional fungicide-treated grapes. Accordingly, antiradical power of wines derived from plant activator-treated grapes, measured by both DPPH (2,2-diphenyl-1-picrylhydrazyl) and the ABTS [(2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] radical-scavenging assay, was higher than in their counterparts. To the best of our knowledge, this is the first report on the effects of agrochemicals on the melatonin content of red wine.

Preharvest L-arginine treatment induced postharvest disease resistance to Botrysis cinerea in tomato fruits

L-arginine is the precursor of nitric oxide (NO). In order to examine the influence of L-arginine on tomato fruit resistance, preharvest green mature tomato fruits (Solanum lycopersicum cv. No. 4 Zhongshu) were treated with 0.5, 1, and 5 mM L-arginine. The reduced lesion size (in diameter) on fruit caused by Botrytis cinerea, as well as activities of phenylalanine ammonia-lyase (PAL), Chitinase (CHI), β-1,3-glucanase (GLU), and polyphenoloxidase (PPO), was compared between L-arginine treated fruits and untreated fruits. We found that induced resistance increased and reached the highest level at 3-6 days after treatment. Endogenous NO concentrations were positively correlated with PAL, PPO, CHI, and GLU activities after treatment with Pearson coefficients of 0.71, 0.94, 0.97, and 0.87, respectively. These results indicate that arginine induces disease resistance via its effects on NO biosynthesis and defensive enzyme activity.