Biomass attachment and microbiota shifts during porcine faecal in vitro fermentation of almond and macadamia nuts differing in particle sizes

Nuts are highly nutritious and good sources of dietary fibre, when consumed as part of a healthy human diet. Upon consumption, nut particles of various sizes containing lipids entrapped by the plant cell walls enter the large intestine where they are fermented by the resident microbiota. This study investigated the microbial community shifts during in vitro fermentation of almond and macadamia substrates, of two particle sizes including fine particles (F = 250-500 μm) and cell clusters (CC = 710-1000 μm). The aim was to determine how particle size and biomass attachment altered the microbiota. Over the 48 h fermentation duration, short chain fatty acid concentrations increased due to particle size rather than nut type (almond or macadamia). However, nut type did change microbial population dynamics by stimulating specific genera. Tyzzerella, p253418B5 gut group, Lachnospiraceae UCG001, Geotrichum, Enterococcus, Amnipila and Acetitomaculum genera were unique for almonds. For macadamia, three unique genera including Prevotellaceae UCG004, Candidatus Methanomethylophilus and Alistipes were noted. Distinct shifts in the attached microbial biomass were noted due to nut particle size. Bacterial attachment to nut particles was visualised in situ during fermentation, revealing a decrease in lipids and an increase in attached bacteria over time. This interaction may be a pre-requisite for lipid breakdown during nut particle disappearance. Overall, this study provides insights into how nut fermentation alters the gut microbiota and the possible role that gut microbes have in lipid degradation.

New Insight into the Effects of Endogenous Protein and Lipids on the Enzymatic Digestion of Starch in Sorghum Flour

The effects of endogenous lipids and protein in sorghum flour on starch digestion were studied following the depletion of lipids and/or protein and after the reconstitution of separated fractions. The removal of protein or lipids moderately increases the digestibility of starch in raw (uncooked) sorghum flour to values close to those for purified starch. Rapid Visco Analyzer data (as a model for the cooking process) show that cooked sorghum flours with lipids have a lower starch digestibility than those without lipids after RVA processing, due to the formation of starch-lipid complexes as evidenced by their higher final viscosity and larger enthalpy changes. Additionally, the formation of a starch-lipid-protein ternary complex was identified in cooked sorghum flour, rather than in a reconstituted ternary mixture, according to the unique cooling stage viscosity peak and a greater enthalpy of lipid complexes. After heating, the sorghum flour showed a lower digestibility than the depleted flours and the reconstituted flours. The results indicate that the natural organization of components in sorghum flour is an important factor in facilitating the interactions between starch, lipids, and protein during RVA processing and, in turn, reducing the starch digestion.

Bringing back a forgotten legume-Sensory profiles of Australian native wattleseeds reveal potential for novel food applications

Documented as one of the oldest living civilizations, there is now evidence that Indigenous communities in Australia followed a sustainable lifestyle with well-designed agricultural practices and adequate physical activity. Commonly known as wattleseeds in Australia, unique cultivars of Acacia have been consumed by Indigenous Australians for over 60,000 years. This research used descriptive sensory profiling to develop a lexicon for the aroma and flavor profiles of four wattleseed species before and after being subjected to different processing techniques. The processing methods selected were pressure cooking, dry roasting, wet roasting, and malting. The species included were Acacia kempeana, Acacia adsurgens, Acacia colei, and Acacia victoriae. Sensory differences were observed between the different cultivars as well as between the different food processing techniques. Results show that wattleseed species diversity is a key driver in determining the aroma profile, while taste profiles are modified by the type of processing method applied. PRACTICAL APPLICATION: This study provides foundational knowledge on these culturally significant seeds, supporting practical opportunities to diversify the uses of wattleseeds in food products.

Characterization of structure-function properties relevant to copper-activated pyrite depression by different starches

Starches can adsorb on and depress copper-activated pyrite desirably during flotation, an important process in ore mineral extraction. In order to develop structure/function relationships, adsorption on and depression properties of copper-activated pyrite at pH 9 by normal wheat starch (NWS) and high-amylose wheat starch (HAW), dextrin, and a range of oxidized normal wheat starches (peroxide and hypochlorite treated) were investigated. Adsorption isotherms and bench flotation performance were compared with kinematic viscosity, molar mass distribution, surface coverage, and substituted functional groups assay. The differences in molar mass distribution and substituted functional groups among oxidized starches had little influence on the depression of copper-activated pyrite. However, the introduction of -C=O and -COOH substituents, combined with depolymerization, improved solubility and dispersibility, reduced aggregated structures, and strengthened surface binding of oxidized polymers, compared with NWS and HAW. At high concentrations, HAW, NWS, and dextrin were adsorbed onto the pyrite surface more than oxidized starches. However, at the low concentrations of depressant used in flotation, oxidized starches were more effective at selectively masking copper sites. This study suggests that a stable chelation between Cu(I) and starch ligands is necessary for depression of copper-activated pyrite at pH 9, which can be achieved with oxidized wheat starch.

Determination of glucosinolates and isothiocyanates in glucosinolate-rich vegetables and oilseeds using infrared spectroscopy: A systematic review

Cruciferous vegetables and oilseeds are rich in glucosinolates that can transform into isothiocyanates upon enzymic hydrolysis during post-harvest handling, food preparation and/or digestion. Vegetables contain glucosinolates that have beneficial bioactivities, while glucosinolates in oilseeds might have anti-nutritional properties. It is therefore important to monitor and assess glucosinolates and isothiocyanates content through the food value chain as well as for optimized crop production. Vibrational spectroscopy methods, such as infrared (IR) spectroscopy, are used as a nondestructive, rapid and low-cost alternative to the current and common costly, destructive, and time-consuming techniques. This systematic review discusses and evaluates the recent literature available on the use of IR spectroscopy to determine glucosinolates and isothiocyanates in vegetables and oilseeds. NIR spectroscopy was used to predict glucosinolates in broccoli, kale, rocket, cabbage, Brussels sprouts, brown mustard, rapeseed, pennycress, and a combination of Brassicaceae family seeds. Only one study reported the use of NIR spectroscopy to predict broccoli isothiocyanates. The major limitations of these studies were the absence of the critical evaluation of errors associated with the reference method used to develop the calibration models and the lack of interpretation of loadings or regression coefficients used to predict glucosinolates.

Effects of incorporating processed Acacia seed as an emulsifying agent on the quality attributes of beef sausage

In this study, partial or full replacement of 6% soy protein isolate (SPI) with 2, 4 and 6% roasted Acacia seed flour (ASRo) and Acacia seed protein concentrates (ASPC) in emulsified beef sausage were investigated. Emulsion stability and cooking loss were lower in samples formulated with ASPC at all levels and control samples compared to ASRo formulated samples. ASRo generated softer and less chewy sausages than ASPC. Cooked 2% ASPC sausages had similar L* and a* values as the control but with lower colour difference (ΔE) values that were similar to cooked 6% SPI sausages' values. An organized protein network structure was observed in the sausages formulated with ASPC at all levels and in the control samples. Therefore, ASPC, particularly at 2 and 4% inclusion, can be used as a functional ingredient to prepare emulsified beef sausages with good quality attributes.

Holistic approach to effects of foods, human physiology, and psychology on food intake and appetite (satiation & satiety)

Appetite (satiation and satiety) is an essential element for the control of eating behavior, and as a consequence human nutrition, body weight, and chronic disease risk. A better understanding of appetite mechanisms is necessary to modulate eating behavior and food intake, and also provide a practical approach for weight management. Although many researchers have investigated the relationships between satiation/satiety and specific factors including human physiology, psychology, and food characteristics, limited information on the interactions between factors or comparisons between the relative importance of factors in contributing to satiation/satiety have been reported. This article reviews progress and gaps in understanding individual attributes contributing to perceived satiation/satiety, the advantages of considering multiple factors together in appetite experiments, as well as the applications of nondestructive sensing in evaluating human factors contributing to relative appetite perception. The approaches proposed position characterization of appetite (satiation and satiety) for personalized and precision nutrition in relation to human status and healthy diets. In particular, it is recommended that future studies of appetite perception recognize the inter-dependence of food type and intake, appetite (satiation and satiety), and individual status.

In vitro fermentation profiles of undigested fractions from legume and nut particles are affected by particle cohesion and entrapped macronutrients

Insoluble undigested food residues are the predominant dietary form of 'fibre' from food plants, with the potential for fermentation by microbial species resident within the large intestine. Here we present results on in vitro fermentation of undigested fractions of legumes (chickpea flour, lentil flour, mung bean flour), and nuts (peanut, almond, macadamia) using a pooled faecal inoculum from pigs fed a nut- and legume-free diet. All substrates were pre-digested in vitro. Nuts were also separated into two particle sizes (PS), cell cluster (CC = 710-1000 μm) and fine (F = 250-500 μm), to test the effect of PS. All substrates tested were fermented for 48 hours, and measured according to gas production, with lentil (within legume flours) being the highest gas producer, and peanut being the highest gas producer within nuts. Undigested fractions from Nuts_F had significantly higher gas production than those from Nuts_CC, consistent with differences in surface area between the two PS. Relative short chain fatty acid concentrations between samples as metabolite end-products were consistent with relative gas production. Analysis of unfermented residues after different fermentation times, showed that cellular integrity was a major factor controlling fermentation rates and that entrapped protein/starch (legumes) and lipid (nuts) all contributed to the fermentation outcomes.

Integrating Effects of Human Physiology, Psychology, and Individual Variations on Satiety–An Exploratory Study

Satiety can influence food intake, and as a consequence has the potential to affect weight and obesity. Human factors such as physiology and psychology are likely to be important in determining satiety. However, it is not well-understood how these factors (individual variations) alone or combined contribute to satiety feelings. In addition, there have been limited or no attempts to use a holistic approach to evaluate satiety. In this study, three plant-based foods were used as mid-morning snack for 52 participants to evaluate satiety response (during three consecutive days, one-day-one-food type). The foods were served ad libitum until participants felt comfortably full prior to satiety monitoring. The study explored diverse human factors (n = 30) that might contribute to satiety including those related to oral physiology, metabolic factors, body composition and psychology. It identified important variables for satiety as well as the interactions among them and the influences of age, gender, and low satiety phenotype (consistently lower reported fullness scores) on satiety. Overall, combinations of factors rather than individual ones contributed to self-reported satiety. Food factors (e.g., type, composition) had limited effects, but there were only three types used in the study. The combination of metabolic factors [respiratory quotient, age, and body energy usage type (e.g., carbohydrate or fat)], oral sensitivity & processing, personality traits (agreeableness, conscientiousness, and neuroticism), and eating behavior (e.g., emotional and external eating) were the most important for explaining individual satiety responses. Older participants had significantly higher reported satiety than younger participants, associated with significant differences in oral physiology, increased body fat, and mature psychological characters. Moreover, different satiety phenotypes had significant differences in relationships with body fat, oral physiology, personalities, food neophobia, and eating behaviors. The results of this study indicate that much greater insights into the factors determining satiety responses can be obtained by combining multiple food and human physiological and psychological characteristics. This study used more diverse measures of individual variation than previous studies of satiety and points the way toward a more holistic approach to understanding the (control of) perceptions of fullness at both individual and group levels.

Effect of processing on the solubility and molecular size of oat β-glucan and consequences for starch digestibility of oat-fortified noodles

White wheat salted noodles containing oats have a slower digestion rate those without oats, with potential health benefits. Oat β-glucan may play an important role in this. Effects of sheeting and shearing during noodle-making and subsequent cooking on β-glucan concentration, solubility, molecular size and starch digestibility were investigated. The levels of β-glucan were reduced by 16% after cooking, due to the loss of β-glucan into the cooking water. Both the noodle-making process and cooking increased the solubility of β-glucan but did not change its average molecular size. Digestion profiles show that β-glucan in wholemeal oat flour did not change starch digestion rates compared with isolated starch, but reduced the starch digestion rate of oat-fortified wheat noodles compared to the control (wheat noodles). Confocal laser scanning microscopy suggests that interaction between β-glucan and protein contributes to the starch-protein matrix and changes noodle microstructure, and thus alters their digestibility.

A preliminary study on the utilisation of near infrared spectroscopy to predict age and in vivo human metabolism

The objective of this study was to evaluate the ability of a portable near infrared (NIR) instrument to analyse different tissues in healthy individuals in vivo and relate the spectral data with age, resting metabolic rate (RMR), respiratory quotient (RQ), body fat (BF) and body mass index (BMI). A NIR (950-1600 nm) instrument was used to collect the spectra of different tissues and partial least squares (PLS) regression was used to relate the NIR with RMR, RQ, BF and BMI. Results shown that non-destructive techniques such as those based in vibrational spectroscopy have potential to be used as tools to better categorise and understand the complex inter-individual differences that determine interactions between physiology and nutrition.

Nutritional, anti-nutritional, antioxidant, physicochemical and functional characterization of Australian acacia seed: effect of species and regions

BACKGROUND

Acacia seed (AS) is an underutilized legume widely distributed in the world, with majority of the species (>70%) found in Australia. Generally, the seeds are not only rich in protein, dietary fibre and potassium, but also possess anti-nutritional compounds. In recent years, there have been an increase in the cultivation of some Australian acacia species such as Acacia victoriae, Acacia cowleana and Acacia coriacea from different regions. However, there is limited information on the composition, anti-nutrients, antioxidant and functional properties of flour from these widely grown Australian AS species. Thus, the present study aimed to assess the properties of these Australian AS species from different geographical regions.

RESULTS

The A. cowleana and A. coriacea were characterized by high protein, fat, potassium and soluble carbohydrate. However, higher starch and fibre contents were present in A. victoriae. Greater amounts of anti-nutrients, total phenolics and flavonoids were found in A. cowleana and A. coriacea seeds, whereas A. victoriae had higher 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity. A. victoriae and A. coriacea demonstrated the highest water absorption and solubility index, respectively. However, A. cowleana showed the highest oil absorption index. There was less variation in the composition and properties within species from different regions.

CONCLUSION

All samples showed promising nutritional characteristics, although with sufficient diversity to indicate that Australian acacia seeds can be utilized to develop a range of new (functional) food products. Overall, the information obtained will help the food industries with the selection of AS species for food application.

Lessons for animal nutrition and production science from the Australian Academy of Science Decadal Plan for the Science of Nutrition

The Australian Academy of Science recently released a Decadal Plan for the Science of Nutrition. This plan was focussed on human nutrition, but it is worth considering implications for production animal science and parallels with animal nutrition. One implication for animal production is the need to understand nutrition for health benefits at the whole-of-diet level rather than as a sum of individual foods or nutrients, providing a driver to studies of human food combinations (meals) as well as of feed ingredient interaction effects in animal diets. A second parallel is in the understanding of differences in individual/genotype responses to food/feed. In humans this is termed personalised nutrition and in animals it is becoming a key driver for genetic selection and nutrition management. A third area involves the need for a Trusted Voice in what is a contested media space for both human foods and animal production. While there are different contexts, there remains much that the animal production nutrition and human nutrition communities can learn from each other.

Molecular-structure evolution during in vitro fermentation of granular high-amylose wheat starch is different to in vitro digestion

This study investigates the evolution of the distributions of whole molecular size and of chain length of granular wheat starches (37 ~ 93% amylose content), subjected to in vitro fermentation with a porcine faecal inoculum or digestion with pancreatic enzymes. The results showed that the molecular structures of high-amylose starch (HAS) unfermented residues largely remained unchanged during the fermentation process, while wild-type starch (37% amylose content) showed a preferential degradation of the amylopectin fraction. In contrast, under simulated digestion conditions, the undigested residues of HAS showed structural changes, including a decrease in amylose content, a shift of amylose peak position towards lower degrees of polymerisation, and an enzyme-resistant fraction. These changes of starch structure are likely to be dependent on the different starch-degrading enzyme activities present in pancreatic vs. microbial systems. Molecular changes in response to fermentation metabolism revealed by size-exclusion chromatography can help understand the microbial utilization of resistant starch.

Towards personalised saliva spectral fingerprints: Comparison of mid infrared spectra of dried and whole saliva samples

The aims of this study were to compare two sample presentations (dry and whole) as well as the effects of both gender and age on the mid infrared (MIR) fingerprint spectra of human saliva. Unstimulated saliva was collected from 52 Female (31 subjects, aged 40.9 ± 14.6 year) and Male (21 subjects, aged 34 ± 11.8 year) participants, stored frozen, and subsequently thawed and analysed by MIR spectroscopy as whole and dried saliva, respectively. Data were analysed by means of principal components analysis (PCA) and partial least squares (PLS) to interpret and compare the effects of presentation (dry vs whole), age and gender on the MIR spectra of saliva. Interpretation of the MIR spectra of both whole and dried samples revealed specific characteristic and different spectral signals when gender and age were compared in the amide I and amide II of proteins (e.g. albumin) and DNA. While whole saliva analysis might be more convenient for rapid test, dried saliva spectra were more consistent across replicates, demonstrating greater ability to distinguish individual differences. The interpretation of the PCA and PLS loadings of both whole and dried saliva samples allowed identification of specific MIR regions associated with age and gender of participants between 1000 cm^-1 and 1800 cm^-1. In particular, the MIR regions associated with the absorption of polysaccharides, glycosylated proteins, and nucleic acid phosphate groups present in saliva were the most dominant. This paper demonstrates that MIR spectroscopy can be used to measure saliva samples and to interpret individual differences in participants due to age in either dry or whole samples. No clear trends were observed in the MIR spectra of the samples associated with gender when all samples were analysed together. However, PLS regression models were able to predict gender in a subset of samples having similar age. The approach described in this study shows promise for potentially using saliva as a tool in food studies (e.g. saliva interactions between food and consumers).

In vitro fermentation outcomes of arabinoxylan and galactoxyloglucan depend on fecal inoculum more than substrate chemistry

Using in vitro fermentation conditions, this study investigated the fermentation characteristics of arabinoxylan (AX) and xyloglucan (XG) with a fecal inoculum that was collected either from humans consuming unrestricted diets or pigs fed a semi-defined diet with cellulose being the sole non-starch polysaccharide for 10 days prior to fecal collection. Metagenomic analysis revealed that microbial communities in the two types of inoculum were distinctively different, which led to distinct fermentation characteristics with the polysaccharides. The microbial communities fermented with the porcine fecal inoculum were clustered according to the fermentation time, while those fermented with the human fecal inoculum were differentiated by the substrates. Using the porcine fecal inoculum, irrespective of the substrates, Prevotella copri and the unclassified lineage rc4-4 were the dominant operational taxonomic units (OTUs) promoted during fermentation. Fermentation of wheat AX (WAX) and galacto-XG (GXG) with the human fecal inoculum, however, promoted different OTUs, except for a shared OTU belonging to Lachnospiraceae. Specifically, WAX promoted the growth of Bacteroides plebeius and a Blautia sp., while GXG promoted an unclassified Bacteroidales, Parabacteroides distasonis, Bacteroides uniformis and Bacteroides sp. 2. These changes in bacterial communities were in accordance with the short chain fatty acid (SCFA) production, where comparable SCFA profiles were obtained from the porcine fecal fermentation while different amounts and proportions of SCFA were acquired from fermentation of WAX and GXG with the human fecal inoculum. Altogether, this study indicated that the starting inoculum composition had a greater effect than polysaccharide chemistry in driving fermentation outcomes.

Interplay between grain digestion and fibre in relation to gastro-small-intestinal passage rate and feed intake in pigs

PURPOSE

The combined effects of grain digestibility and dietary fibre on digesta passage rate and satiety in humans are poorly understood. Satiety can be increased through gastric distention, reduced gastric emptying rate and when partially digested nutrients reach the terminal ileum to stimulate peptide release through the ileal/colonic brakes to slow the rate of digesta passage. This study determined the effects of grain digestibility and insoluble fibre on mean retention time (MRT) of digesta from mouth-to-ileum, feed intake (FI), starch digestion to the terminal ileum and faecal short chain fatty acids (SCFA) in a pig model.

METHOD

Twelve grain-based [milled sorghum (MS), steam-flaked-sorghum, milled wheat, and steam-flaked-wheat (SFW)] diets with different intrinsic rates of starch digestion, assessed by apparent amylase diffusion coefficient (ADC), and fibre from oat hulls (OH) at 0, 5 and 20% of the diet were fed to ileal-cannulated pigs.

RESULT

MRT was affected by grain-type/processing (P < 0.05) and fibre amount (P < 0.05). An approximate tenfold increase in ADC showed a limited decline in MRT (P = 0.18). OH at 20% increased MRT (P < 0.05) and reduced FI (P < 0.05). Ileal digestibility of starch increased and faecal SCFA concentration decreased with ADC; values for MS being lower (P < 0.001) and higher (P < 0.05), respectively, than for SFW.

CONCLUSIONS

Lower ileal digestibility of starch, higher faecal SCFA concentration and longer MRT of MS than SFW, suggest the ileal/colonic brakes may be operating. FI appeared to decrease with increasing MRT. MRT increased and intake decreased with grain-based foods/feeds that have low starch digestibility and substantial amounts of insoluble fibre.

Interaction of cellulose and xyloglucan influences in vitro fermentation outcomes

To investigate the effects of interactions between cellulose and xyloglucan (XG) on in vitro fermentation, a composite of bacterial cellulose (BC) incorporating XG during pellicle formation (BCXG), was fermented using a human faecal inoculum, and compared with BC, XG and a mixture (BC&XG) physically blended to have the same BC to XG ratio of BCXG. Compared to individual polysaccharides, the fermentation extent of BC and fermentation rate of XG were promoted in BC&XG. XG embedded in the BCXG composite was degraded less than in BC&XG, while more cellulose in BCXG was fermented than in BC&XG. This combination explains the similar amount of short chain fatty acid production noted throughout the fermentation process for BCXG and BC&XG. Microbial community dynamics for each substrate were consistent with the corresponding polysaccharide degradation. Thus, interactions between cellulose and XG are shown to influence their fermentability in multiple ways.

Depletion and bridging flocculation of oil droplets in the presence of β-glucan, arabinoxylan and pectin polymers: Effects on lipolysis

The aim of this study was to investigate the influence of food polysaccharides from different sources on microstructural and rheological properties, and in vitro lipolysis of oil-in-water emulsions of canola oil stabilised by whey protein isolate. The polysaccharides used were β-glucan (BG) from oat, arabinoxylan (AX) from wheat, and pectin (PTN) from apple. All polysaccharides added at 1 % w/v increased the viscosity of emulsions and promoted flocculation but with different mechanisms, BG and AX by depletion flocculation and PTN by bridging flocculation. Depletion flocculation was associated with an increase in viscosity of BG or AX-stabilised emulsions compared with BG/AX alone, whereas bridging flocculation with PTN caused a decrease in viscosity. All three polysaccharides reduced lipid digestion rate and extent, but the bridging flocculation induced by PTN had the greatest effect. This study has implications for better understanding the influence of carbohydrate polymers from cereals and fruits on lipid digestibility.

Wheat cell walls and constituent polysaccharides induce similar microbiota profiles upon in vitro fermentation despite different short chain fatty acid end-product levels

Plant cell walls as well as their component polysaccharides in foods can be utilized to alter and maintain a beneficial human gut microbiota, but it is not known whether the architecture of the cell wall influences the gut microbiota population. In this study, wheat flour cell walls (WCW) were isolated and compared with their major constituents - arabinoxylan (AX), mixed linkage (1,3)(1,4)-β-glucan (MLG) and cellulose - both separately and as a physical mixture of polysaccharides (Mix) equivalent in composition to WCW. These samples underwent in vitro fermentation with a faecal inoculum from pigs fed a diet free of cereals and soluble-fibre to avoid prior adaptation to substrates. During fermentation, samples were collected for DNA extraction and 16S rRNA gene amplicon sequencing. Bioinformatics analyses revealed that the microbial communities promoted during fermentation by AX, MLG, Mix and WCW were similar at the genus level, but differed from the microbiota observed for the cellulose substrate. Differences in proportions of propionate and butyrate end-products were associated with differences in the relative levels of genera. These findings show that, in this experiment, the microbes that flourished were able to utilize diverse WCW polysaccharides alone, in mixtures or in intact cell walls in a similar way, but that different fermentation end-products were associated with AX (propionate) or MLG (butyrate) polysaccharides.

Metabolism of Black Carrot Polyphenols during In Vitro Fermentation is Not Affected by Cellulose or Cell Wall Association

Fruit and vegetable polyphenols are associated with health benefits, and those not absorbed could be fermented by the gastro-intestinal tract microbiota. Many fermentation studies focus on "pure" polyphenols, rather than those associated with plant cell walls (PCW). Black carrots (BlkC), are an ideal model plant food as their polyphenols bind to PCW with minimal release after gastro-intestinal digestion. BlkC were fractionated into three components-supernatant, pellet after centrifugation, and whole puree. Bacterial cellulose (BCell) was soaked in supernatant (BCell&S) as a model substrate. All substrates were fermented in vitro with a pig faecal inoculum. Gas kinetics, short chain fatty acids, and ammonium production, and changes in anthocyanins and phenolic acids were compared. This study showed that metabolism of BlkC polyphenols during in vitro fermentation was not affected by cellulose/cell wall association. In addition, BCell&S is an appropriate model to represent BlkC fermentation, suggesting the potential to examine fermentability of PCW-associated polyphenols in other fruits/vegetables.

The contribution of β-glucan and starch fine structure to texture of oat-fortified wheat noodles

Wheat flour noodles are sometimes fortified with β-glucan for nutritional value, but this can decrease eating quality. The contributions of β-glucan and starch molecular fine structure to physicochemical properties of wholemeal oat flour and to the texture of oat-fortified white salted noodles were investigated here. Hardness of oat-fortified noodles was controlled by the longer amylopectin chains (DP ≥ 26) and amount of longer amylose chains (DP ≥ 1000). Higher levels of β-glucan, in the range from 3.1 to 5.2%, result in increased noodle hardness. Pasting viscosities of wholemeal oat flour positively correlate with the hardness of oat-fortified noodles. The swelling power of oat flour is not correlated with either pasting viscosities of oat flour or noodle hardness. Longer amylopectin chains and the amount of longer amylose chains both control the pasting viscosities of oat flour, which in turn affect noodle texture. This provides new means, based on starch and β-glucan molecular structure, to choose oats with optimal starch structure and β-glucan content for targeted oat-fortified noodle quality.

Protein-starch matrix plays a key role in enzymic digestion of high-amylose wheat noodle

Wheat flour, consisting of a complex matrix of starch and protein, is used as a representative model of whole food here to investigate the binary interaction in relation to amylose level and hydrothermal treatment in noodles as a food exemplar. Noodle made of high-amylose wheat (HAW) flour showed an eight-fold higher resistant starch content, compared to the wild type. Protein removal under simulated intestinal digestion conditions resulted in higher starch digestion rate coefficients in raw and cooked flours. In cooked flours, the substrate becomes similarly accessible to digestive enzymes regardless of protein removal. The results indicate that the increased protein content in native HAW flour and thermal stability of starch in HAW noodles lead to higher food integrity and consequently enhance the resistance against α-amylase digestion. Overall, the study suggests that a diversity of starch-protein interactions in wheat-based food products underlies the nutritional value of natural whole foods.

Functional Genomic Validation of the Roles of Soluble Starch Synthase IIa in Japonica Rice Endosperm

The enzyme starch synthase IIa (SSIIa) in cereals has catalytic and regulatory roles during the synthesis of amylopectin that influences the functional properties of the grain. Rice endosperm SSIIa is more active in indica accessions compared to japonica lines due to functional SNP variations in the coding region of the structural gene. In this study, downregulating the expression of japonica-type SSIIa in Nipponbare endosperm resulted in either shrunken or opaque grains with an elevated proportion of A-type starch granules. Shrunken seeds had severely reduced starch content and could not be maintained in succeeding generations. In comparison, the opaque grain morphology was the result of weaker down-regulation of SSIIa which led to an elevated proportion of short-chain amylopectin (DP 6-12) and a concomitant reduction in the proportion of medium-chain amylopectin (DP 13-36). The peak gelatinization temperature of starch and the estimated glycemic score of cooked grain as measured by the starch hydrolysis index were significantly reduced. These results highlight the important role of medium-chain amylopectin in influencing the functional properties of rice grains, including its digestibility. The structural, regulatory and nutritional implications of down-regulated japonica-type SSIIa in rice endosperm are discussed.

Wheat bran and oat hulls have dose-dependent effects on ad-libitum feed intake in pigs related to digesta hydration and colonic fermentation

Undigested nutrients and fermentable fibre in the distal ileum and colon stimulate intestinal brakes, which reduce gastric-emptying and digesta-passage-rate, and subsequently limit feed/food-intake. Fibre can also stimulate passage rate potentially increasing feed intake (FI). In order to experimentally determine the relationships between these two hypothesised actions of fibre, five levels of wheat-bran (WB) or oat-hulls (OH) were added to a highly digestible starch-based diet fed to pigs ad-libitum for three weeks. Average-daily-feed-intake (ADFI), faecal short-chain-fatty-acids (SCFA) and related parameters were determined at 7, 14 and 21d. A linear mixed model was fitted to FI and fermentation parameters. Overall, WB diets showed 8-11% lower ADFI (7-14d: p < 0.05; 7-21 & 0-21d: p = 0.053) than OH diets. WB diets produced over 20% more (21d: p < 0.01) SCFA than OH or Control diets. WB at 25% produced 22% more (7d: p < 0.05) SCFA than any other diet. Diets with WB at 25 and 35%, showed higher hydration capacity than any other diet (p < 0.001). OH at 10% had an unusually low FI and a markedly higher hydration capacity. With increasing levels of OH, intake of base diet was 7% more than control at 5% OH, but 8% less than control at 20% OH. With increasing WB content, intake of base diet decreased. From these results, we propose that three mechanisms control the effects of fibre on FI: initial increase in passage rate and feed intake at low concentrations of non-swelling fibres; a depression in FI from high fibre bulk; and reduced feed intake from stimulation of ileal and colonic brakes.

In Vitro Digestion of Apple Tissue Using a Dynamic Stomach Model: Grinding and Crushing Effects on Polyphenol Bioaccessibility

Food structure is a key determinant for the release of phenolic compounds during gastric and intestinal digestion. We evaluated the bioaccessibility of polyphenols from apple tissue during gastric digestion in vitro from bio-mechanical perspectives including the effects of gastric juice and mucin on the apple tissue matrix under simulated stomach peristalsis. The gastric model system was effective in releasing polyphenols because of simultaneous compression and extrusion, with 3 times higher release from coarse than from fine particles. However, bioaccessibility of polyphenols was reduced up to 44% in the presence of both cell walls and gastric mucin. Most individual phenolic molecules were gradually released and were stable in the gastric environment, except for procyanidin B2. The study suggests that the bioaccessibility of polyphenols from apples in the upper digestive tract is dependent on mechanical disintegration and the residual matrix present in the swallowed bolus.

High amylose wheat starch structures display unique fermentability characteristics, microbial community shifts and enzyme degradation profiles

In vitro fermentation of wheat starch depends on amylose content in cooked but not granule forms, and shows that high amylose wheat is a promising source of fermentable carbohydrate in the large intestine.

Purified plant cell walls with adsorbed polyphenols alter porcine faecal bacterial communities during in vitro fermentation

A simplified in vitro model to indicate microbiota changes to polyphenols associated with dietary fibre in whole fruits, noting differences in bacterial populations between polyphenolic groups during fermentation.

Formation of Cellulose-Based Composites with Hemicelluloses and Pectins Using Komagataeibacter Fermentation

Komagataeibacter xylinus synthesizes cellulose in an analogous fashion to plants. Through fermentation of K. xylinus in media containing cell wall polysaccharides from the hemicellulose and/or pectin families, composites with cellulose can be produced. These serve as general models for the assembly, structure, and properties of plant cell walls. By studying structure/property relationships of cellulose composites, the effects of defined hemicellulose and/or pectin polysaccharide structures can be investigated. The macroscopic nature of the composites also allows composite mechanical properties to be characterized.The method for producing cellulose-based composites involves reviving and then culturing K. xylinus in the presence of desired hemicelluloses and/or pectins. Different conditions are required for construction of hemicellulose- and pectin-containing composites. Fermentation results in a floating mat or pellicle of cellulose-based composite that can be recovered, washed, and then studied under hydrated conditions without any need for intermediate drying.