Evaluation of the prebiotic potential of five kiwifruit cultivars after simulated gastrointestinal digestion and fermentation with human faecal bacteria

Microbiological and Chemical Profiles of Kiwi Kefir-like Beverages Produced Using Different Agitation Speeds and Kefir Grain Weights

This study aimed to identify kiwi kefir-like beverages with high levels of viable probiotic cells and low levels of calories, acids, and alcohol. To achieve this, microbiological and chemical characterizations were conducted on beverages inoculated with varying amounts of kefir grains (GW) and incubated at different agitation speeds (A), following a second-order orthogonal factorial design. For each experimental condition, three 24-h batch cultures were performed using three successive passages of kefir grains. Higher GW levels promoted greater nutrient consumption and metabolite production. However, an intermediate GW (1.80 g) resulted in the highest growth of lactic acid bacteria (LAB), acetic acid bacteria (AAB), yeasts, and free biomass in the fermented medium. Optimal agitation levels also enhanced nutrient consumption, free biomass, and metabolite pro-duction. AAB and yeast counts increased with higher agitation speeds, while LAB counts de-creased. Three beverages, produced during the second (A = 86 rpm, GW = 2.81 g) and third (A = 38 rpm, GW = 2.60 g; A = 86 rpm, GW = 1.80 g) kefir grain passages, exhibited LAB and yeast counts above 106; CFU/mL, along with low total sugar and ethanol concentrations. These beverages may be considered suitable as potentially probiotic, low-alcohol, and low-calorie functional drinks.

Butyrogenic, bifidogenic and slight anti-inflammatory effects of a green kiwifruit powder (Kiwi FFG®) in a human gastrointestinal model simulating mild constipation

Green kiwi (Actinidia deliciosa var. Hayward) is a fruit with important nutritional attributes and traditional use as a laxative. In this work, we studied in vitro the colonic fermentation of a standardized green kiwifruit powder (Kiwi FFG®) using representative intestinal microbial content of mildly constipated women. Static (batch) and dynamic configurations of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) were used to estimate the impact of Kiwi FFG® in the human gut. Analysis of metabolites revealed a significant butyrogenic effect of the kiwifruit powder and, consistently, butyrate-producing bacterial populations (i.e., Faecalibacterium prausnitzii, Cluster IV, Roseburia spp.) were greatly increased in the dynamic gastrointestinal model. Bifidobacterium spp. was also found boosted in the microflora of ascending and transverse colon sections, and a significant rise of Akkermansia muciniphila was identified in the transverse colon. Reporter gene assays using human intestinal cells (HT-29) showed that kiwifruit fermentation metabolites activate the aryl hydrocarbon receptor (AhR) transcriptional pathway, which is an important regulator of intestinal homeostasis and immunity. Moreover, modulation in the production of human interleukins (IL-6 and IL-10) in Caco-2 cells suggested a potential mild anti-inflammatory effect of the kiwifruit powder and its gut microbiota-derived metabolites. Our results suggested a potential health benefit of Kiwi FFG® in the gut microbiota, particularly in the context of constipated people.

Recent Innovations in Non-dairy Prebiotics and Probiotics: Physiological Potential, Applications, and Characterization

Non-dairy sources of prebiotics and probiotics impart various physiological functions in the prevention and management of chronic metabolic disorders, therefore nutraceuticals emerged as a potential industry. Extraction of prebiotics from non-dairy sources is economical and easily implemented. Waste products during food processing, including fruit peels and fruit skins, can be utilized as a promising source of prebiotics and considered "Generally Recognized As Safe" for human consumption. Prebiotics from non-dairy sources have a significant impact on gut microbiota and reduce the population of pathogenic bacteria. Similarly, next-generation probiotics could also be isolated from non-dairy sources. These sources have considerable potential and can give novel strains of probiotics, which can be the replacement for dairy sources. Such strains isolated from non-dairy sources have good probiotic properties and can be used as therapeutic. This review will elaborate on the potential non-dairy sources of prebiotics and probiotics, their characterization, and significant physiological potential.

Valorization of Fruit Waste for Bioactive Compounds and Their Applications in the Food Industry

The fruit production and processing sectors produce tremendous amounts of by-products and waste that cause significant economic losses and an undesirable impact on the environment. The effective utilization of these fruit wastes can help to reduce the carbon footprint and greenhouse gas emissions, thereby achieving sustainable development goals. These by-products contain a variety of bioactive compounds, such as dietary fiber, flavonoids, phenolic compounds, antioxidants, polysaccharides, and several other health-promoting nutrients and phytochemicals. These bioactive compounds can be extracted and used as value-added products in different industrial applications. The bioactive components extracted can be used in developing nutraceutical products, functional foods, or food additives. This review provides a comprehensive review of the recent developments in fruit waste valorization techniques and their application in food industries. The various extraction techniques, including conventional and emerging methods, have been discussed. The antioxidant and antimicrobial activities of the active compounds extracted and isolated from fruit waste have been described. The most important food industrial application of bioactive compounds extracted from fruit waste (FW) has been provided. Finally, challenges, future direction, and concluding remarks on the topic are summarized.

Ultrasound-Assisted Extraction, Identification, and Quantification of Antioxidants from 'Jinfeng' Kiwifruit

Kiwifruit (Actinidia chinensis) is a nutrient-dense fruit abundant in vitamin C and phenolic compounds, and it exhibits strong antioxidant capacity. However, the antioxidants in 'Jinfeng' kiwifruit have seldom been extracted and analyzed, and the conditions for the extraction of kiwifruit antioxidants by ultrasound-assisted extraction (UAE) have seldom been investigated. In this study, response surface methodology (RSM) was used to optimize UAE conditions to extract antioxidants from 'Jinfeng' kiwifruit. In addition, the antioxidant capacity, contents of total phenolics and total flavonoids, ascorbic acid, and the profiles of antioxidants were also analyzed. The results showed that the optimal UAE conditions included 68% ethanol, liquid/solid ratio at 20 mL/g, extraction time at 30 min, extraction temperature at 42 °C, and ultrasonic power at 420 W. Under these conditions, the ABTS value of kiwifruit was 70.38 ± 1.38 μM TE/g DW, which was 18.5% higher than that of the extract obtained by conventional solvent extraction. The total phenolic and flavonoid contents were 15.50 ± 0.08 mg GAE/g DW and 5.10 ± 0.09 mg CE/g DW, respectively. Moreover, 20 compounds were tentatively identified by UPLC-MS/MS, and the content of main compounds, such as procyanidin B2, neochlorogenic acid, and epicatechin, were determined by HPLC-DAD. This research revealed the profiles of antioxidant phytochemicals in 'Jinfeng' kiwifruit, which can be a good dietary source of natural antioxidants with potential health functions.

Valorization of kiwi agricultural waste and industry by-products by recovering bioactive compounds and applications as food additives: A circular economy model

Currently, agricultural production generates large amounts of organic waste, both from the maintenance of farms and crops (agricultural wastes) and from the industrialization of the product (food industry waste). In the case of Actinidia cultivation, agricultural waste groups together leaves, flowers, stems and roots while food industry by-products are represented by discarded fruits, skin and seeds. All these matrices are now underexploited and so, they can be revalued as a natural source of ingredients to be applied in food, cosmetic or pharmaceutical industries. Kiwifruit composition (phenolic compounds, volatile compounds, vitamins, minerals, dietary fiber, etc.) is an outstanding basis, especially for its high content in vitamin C and phenolic compounds. These compounds possess antioxidant, anti-inflammatory or antimicrobial activities, among other beneficial properties for health, but stand out for their digestive enhancement and prebiotic role. Although the biological properties of kiwi fruit have been analyzed, few studies show the high content of compounds with biological functions present in these by-products. Therefore, agricultural and food industry wastes derived from processing kiwi are regarded as useful matrices for the development of innovative applications in the food (pectins, softeners, milk coagulants, and colorants), cosmetic (ecological pigments) and pharmaceutical industry (fortified, functional, nutraceutical, or prebiotic foods). This strategy will provide economic and environmental benefits, turning this industry into a sustainable and environmentally friendly production system, promoting a circular and sustainable economy.

Chewing differences in consumers affect the digestion and colonic fermentation outcomes: In vitro studies

It is important to understand variability in consumer chewing behavior for designing food products that deliver desired functionalities for target consumer segments. In this study, we selected 29 participants, representing...

Complementary Food Ingredients Alter Infant Gut Microbiome Composition and Metabolism In Vitro

We examined the prebiotic potential of 32 food ingredients on the developing infant microbiome using an in vitro gastroileal digestion and colonic fermentation model. There were significant changes in the concentrations of short-chain fatty-acid metabolites, confirming the potential of the tested ingredients to stimulate bacterial metabolism. The 16S rRNA gene sequencing for a subset of the ingredients revealed significant increases in the relative abundances of the lactate- and acetate-producing Bifidobacteriaceae, Enterococcaceae, and Lactobacillaceae, and lactate- and acetate-utilizing Prevotellaceae, Lachnospiraceae, and Veillonellaceae. Selective changes in specific bacterial groups were observed. Infant whole-milk powder and an oat flour enhanced Bifidobacteriaceae and lactic acid bacteria. A New Zealand-origin spinach powder enhanced Prevotellaceae and Lachnospiraceae, while fruit and vegetable powders increased a mixed consortium of beneficial gut microbiota. All food ingredients demonstrated a consistent decrease in Clostridium perfringens, with this organism being increased in the carbohydrate-free water control. While further studies are required, this study demonstrates that the selected food ingredients can modulate the infant gut microbiome composition and metabolism in vitro. This approach provides an opportunity to design nutrient-rich complementary foods that fulfil infants’ growth needs and support the maturation of the infant gut microbiome.

The sugar composition of the fibre in selected plant foods modulates weaning infants' gut microbiome composition and fermentation metabolites in vitro

Eight plant-based foods: oat flour and pureed apple, blackcurrant, carrot, gold- and green-fleshed kiwifruit, pumpkin, sweetcorn, were pre-digested and fermented with pooled inocula of weaning infants’ faecal bacteria in an in vitro hindgut model. Inulin and water were included as controls. The pre-digested foods were analysed for digestion-resistant fibre-derived sugar composition and standardised to the same total fibre concentration prior to fermentation. The food-microbiome interactions were then characterised by measuring microbial acid and gas metabolites, microbial glycosidase activity and determining microbiome structure. At the physiologically relevant time of 10 h of fermentation, the xyloglucan-rich apple and blackcurrant favoured a propiogenic metabolic and microbiome profile with no measurable gas production. Glucose-rich, xyloglucan-poor pumpkin caused the greatest increases in lactate and acetate (indicative of high fermentability) commensurate with increased bifidobacteria. Glucose-rich, xyloglucan-poor oats and sweetcorn, and arabinogalactan-rich carrot also increased lactate and acetate, and were more stimulatory of clostridial families, which are indicative of increased microbial diversity and gut and immune health. Inulin favoured a probiotic-driven consortium, while water supported a proteolytic microbiome. This study shows that the fibre-derived sugar composition of complementary foods may shape infant gut microbiome structure and metabolic activity, at least in vitro.

Actinidia arguta Sprout as a Natural Antioxidant: Ameliorating Effect on Lipopolysaccharide-Induced Cognitive Impairment

Here, we investigated the prebiotic and antioxidant effects of Actinidia arguta sprout water extract (AASWE) on lipopolysaccharide (LPS)-induced cognitive deficit mice. AASWE increased viable cell count, titratable acidity, and acetic acid production in Lactobacillus reuteri strain and showed a cytoprotective effect on LPS-induced inflammation in HT-29 cells. We assessed the behavior of LPSinduced cognitive deficit mice using Y-maze, passive avoidance and Morris water maze tests and found that administration of AASWE significantly improved learning and memory function. The AASWE group showed antioxidant activity through downregulation of malondialdehyde levels and upregulation of superoxide dismutase levels in brain tissue. In addition, the AASWE group exhibited activation of the cholinergic system with decreased acetylcholinesterase activity in brain tissue. Furthermore, AASWE effectively downregulated inflammatory mediators such as phosphorylated- JNK, phosphorylated-NF-κB, TNF-α and interleukin-6. The major bioactive compounds of AASWE were identified as quercetin-3-O-arabinopyranosyl(1→2)-rhamnopyranosyl(1→6)-glucopyranose, quercetin-3-O-apiosyl(1→2)-galactoside, rutin, and 3-caffeoylquinic acid. Based on these results, we suggest that AASWE not only increases the growth of beneficial bacteria in the intestines, but also shows an ameliorating effect on LPS-induced cognitive impairment.

Bioaminergic Responses in an In Vitro System Studying Human Gut Microbiota-Kiwifruit Interactions

Whole kiwifruit ('Hayward' and 'Zesy002') were examined for their bioaminergic potential after being subjected to in vitro gastrointestinal digestion and colonic fermentation. Controls included the prebiotic inulin and water, a carbohydrate-free vehicle. The dopamine precursor l-dihydroxyphenylalanine (L-DOPA) and the serotonin precursor 5-hydroxytryptophan were increased in the kiwifruit gastrointestinal digesta ('Hayward' > 'Zesy002') in comparison to the water digesta. Fermentation of the digesta with human fecal bacteria for 18 h modulated the concentrations of bioamine metabolites. The most notable were the significant increases in L-DOPA ('Zesy002' > 'Hayward') and γ-aminobutyric acid (GABA) ('Hayward' > 'Zesy002'). Kiwifruit increased Bifidobacterium spp. and Veillonellaceae (correlating with L-DOPA increase), and Lachnospira spp. (correlating with GABA). The digesta and fermenta were incubated with Caco-2 cells for 3 h followed by gene expression analysis. Effects were seen on genes related to serotonin synthesis/re-uptake/conversion to melatonin, gut tight junction, inflammation and circadian rhythm with different digesta and fermenta from the four treatments. These indicate potential effects of the substrates and the microbially generated organic acid and bioamine metabolites on intestinal functions that have physiological relevance. Further studies are required to confirm the potential bioaminergic effects of gut microbiota-kiwifruit interactions.

Influence of kiwifruit on gastric and duodenal inflammation-related gene expression in aspirin-induced gastric mucosal damage in rats

Kiwifruit (KF) contains bioactive compounds with potential anti-inflammatory properties. In this study, we investigated the protective effects of KF on gastric and duodenal damage induced by soluble aspirin in healthy rats. Sixty-four male Sprague Dawley rats were allocated to eight experimental treatments (n = 8) and the experimental diets were fed for 14 days ad libitum. The experimental diets were 20% fresh pureed KF (green-fleshed and gold-fleshed) or 10% glucose solution (control diet). A positive anti-inflammatory control treatment (ranitidine) was included. At the end of the 14-day feeding period, the rats were fasted overnight, and the following morning soluble aspirin (400 mg/kg aspirin) or water (control) was administered by oral gavage. Four hours after aspirin administration, the rats were euthanized and samples taken for analysis. We observed no significant ulcer formation or increase in infiltration of the gastric mucosal inflammatory cells in the rats with the aspirin treatment. Despite this, there were significant changes in gene expression, such as in the duodenum of aspirin-treated rats fed green KF where there was increased expression of inflammation-related genes NOS2 and TNF-alpha. We also observed that gold and green KF diets had a number of contrasting effects on genes related to inflammation and gastro-protective effects.

Potential prebiotic effect of fruit and vegetable byproducts flour using in vitro gastrointestinal digestion

Fruit and vegetable byproducts (FVBP) present high content of bioactive compounds and dietary fibers and have demonstrated a positive modulatory effect upon gut microbiota composition. In the present study, the prebiotic potential of a FVBP flour obtained from solid byproducts after fruit and vegetable processing was evaluated after in vitro gastrointestinal digestion. An initial screening with three strains of Lactobacillus (Lactobacillus casei 01, Lactobacillus rhamnosus R11 and Lactobacillus acidophilus LA-5®) and one Bifidobacterium strain (Bifidobacterium animalis spp. lactis BB12®) was carried out and then the prebiotic effect of FVBP flour was performed with fecal samples of five donors. The changes in gut microbiota were evaluated at 0, 12, 24 and 48 h of fermentation by the real-time polymerase chain reaction (qPCR) method with 16S rRNA-based specific primers. The pH and short chain fatty acids (SCFA) production at each fermentation time were assessed. The fructooligosaccharides (FOS) were used as positive control. The impact of FVBP flour upon cell viability was also evaluated. FVBP flour showed higher prebiotic effect than FOS on growth enhancement of Lactobacillus after 48 h of fermentation and similar bifidogenic effect as FOS on Bifidobacterium growth at 12, 24 and 48 h of fermentation. SCFA production was observed when FVBP flour was used as carbon source, including butyrate, which supports the prebiotic potential of this flour. Additionally, it was observed that after in vitro gastrointestinal digestion, the FVBP flour at 3% promoted cell metabolism of Caco-2 cell line up to 67%. Thus, the present study demonstrates the viability of using a fruit and vegetable byproducts flour as a potential sustainable prebiotic source.

Developments in understanding and applying prebiotics in research and practice-an ISAPP conference paper

AIMS

The concept of using specific dietary components to selectively modulate the gut microbiota to confer a health benefit, defined as prebiotics, originated in 1995. In 2018, a group of scientists met at the International Scientific Association for Probiotics and Prebiotics annual meeting in Singapore to discuss advances in the prebiotic field, focussing on issues affecting functionality, research methodology and geographical differences.

METHODS AND RESULTS

The discussion ranged from examining scientific literature supporting the efficacy of established prebiotics, to the prospects for establishing health benefits associated with novel compounds, isolated from different sources.

CONCLUSIONS

While many promising candidate prebiotics from across the globe have been highlighted in preliminary research, there are a limited number with both demonstrated mechanism of action and defined health benefits as required to meet the prebiotic definition. Prebiotics are part of a food industry with increasing market sales, yet there are great disparities in regulations in different countries. Identification and commercialization of new prebiotics with unique health benefits means that regulation must improve and remain up-to-date so as not to risk stifling research with potential health benefits for humans and other animals.

SIGNIFICANCE AND IMPACT OF STUDY

This summary of the workshop discussions indicates potential avenues for expanding the range of prebiotic substrates, delivery methods to enhance health benefits for the end consumer and guidance to better elucidate their activities in human studies.