The impact of dietary fibre intake on the physiology and health of the stomach and upper gastrointestinal tract

Fractionation and physicochemical characterization of dietary fiber of kenaf (Hibiscus cannabinus L.) seed

BACKGROUND

Kenaf seeds are underutilized kenaf plant by-products, containing essential nutrients including dietary fiber (DF), which can be potentially utilized as food ingredients. The present study aimed to evaluate the physicochemical characteristics of kenaf seed fiber fractions extracted from kenaf seed.

RESULTS

Defatted kenaf seed powder yielded four DF fractions: alkali-soluble hemicellulose (146.4 g kg-1 ), calcium-bound pectin (10.3 g kg-1 ) and acid-soluble pectin (25.4 g kg-1 ) made up the soluble fibre fraction, whereas cellulose (202.2 g kg-1 ) comprised the insoluble fraction. All fractions were evaluated for their physicochemical properties. The DF fractions contained glucose, mannose, xylose and arabinose, and a small amount of uronic acid (1.2-2.7 g kg-1 ). The isolated pectin fractions had a low degree of esterification (14-30%). All the isolated DF fractions had high average molecular weights ranging from 0.3 to 4.3 × 106 g mol-1 . X-ray diffractogram analysis revealed that the fractions consisted mainly of an amorphous structure with a relative crystallinity ranging from 31.6% to 44.1%. The Fourier-transform infrared spectroscopy spectrum of kenaf seed and its DF fractions showed typical absorption of polysaccharides, with the presence of hydroxyl, carboxyl, acetyl and methyl groups. Scanning electron microscopy analysis demonstrated that the raw material with the rigid structure resulted in soluble and insoluble DF fractions with more fragile and fibrous appearances, respectively. The soluble DF demonstrated greater flowability and compressibility than the insoluble fractions.

CONCLUSION

These findings provide novel information on the DF fractions of kenaf seeds, which could be used as a potential new DF for the food industry. © 2023 Society of Chemical Industry.

Association of Gastric Myoelectric Activity with Dietary Intakes, Substrate Utilization, and Energy Expenditure in Adults with Obesity

Obesity can modulate gastric myoelectric activity (GMA); however, the relationship of GMA with nutrient intakes and substrate utilization in adults with obesity is lacking. We examined the association of dietary intakes, energy expenditure, and substrate utilization with the GMA. Participants (n = 115, 18−60 y) were divided into healthy weight (HW, n = 24), overweight (OW, n = 29), obese (OB, n = 41) and morbidly obese (MO, n = 21). Two-day multi-pass 24 h recalls were conducted. The GMA was measured by multichannel electrogastrography (EGG) with water-load (WL) testing. Resting metabolic rate (RMR) and percentages of substrate utilization were measured by indirect calorimetry. In the HW, protein intake was directly correlated with average dominant frequency (ADF) and with WL volume, while in obese participants and the MO subgroup, WL volume correlated with carbohydrate intake. In participants with obesity, ADF was positively correlated with fiber intake. In participants with obesity and the OB subgroup, RMR was positively correlated with water-load volume (r = 0.39 and 0.37, p < 0.05). The ADF showed negative correlations with percent of fat utilization and positive correlations with percent of CHO utilization in non-obese groups. However, protein utilization showed inverse correlation in all obese groups. In conclusion, these distinctive associations suggest that certain dietary compositions and dieting regimens impact GMA patterns.

Influence of native cellulose, microcrystalline cellulose and soluble cellodextrin on inhibition of starch digestibility

Cellulose is a major component of dietary fiber and it is proved to influence starch digestibility. The effects of native cellulose (NC), microcrystalline cellulose (MC), soluble cellodextrin (SC) on starch digestion have not been clearly elucidated. In this study, three types of cellulose with representative molecular weights (NC, 422500 Da; MC, 27750 Da; SC, 2202 Da) were prepared and their effects on starch digestion, glucose diffusion, α-amylase and amyloglucosidase activity were compared. The results suggested SC inhibited starch digestibility to a greater degree than those of NC and MC. When addition of SC reached 3 %, rapidly digestible starch proportion decreased from 31.2 % to 11.3 % and resistant starch proportion increased from 15.0 % to 58.0 %. Notably, hindrance effects of SC on glucose diffusion were higher than those of NC and MC. Moreover, SC reduced activity of α-amylase and amyloglucosidase to a larger extent than those of MC and NC. With the effect of starch digestion inhibition, NC, MC and SC could be utilized as functional food ingredients. Especially, the soluble property and the highest starch digestion inhibition ability of SC favors its application in food industry.

In vitro digestion of tofu with different textures using an artificial gastric digestive system

Two kinds of tofu with obvious differences in texture ["GDL" and "CaSO₄", standing for tofus made with the application of either glucono-δ-lactone (GDL) or calcium sulfate, with measured hardness 23.1 ± 3.3 g and 105.2 ± 25.1 g, respectively] were used as to investigate the in vitro progress and extent of tofu digestion, using an independently-developed artificial gastric digestion system (AGDS). The particle size distributions of both CaSO₄ and GDL tofu shifted towards smaller particles as the digestion time increased, while the viscosity of the gastric digesta also increased. Tofu proteins were hydrolyzed in the simulated stomach, with GDL tofu showing a higher hydrolysis rate, based on the temporal evolution of SDS-PAGE bands, and had a higher amino acids accumulation than CaSO₄ tofu at the end of gastric digestion. In the absence of peptic enzymes, the protein was acidically-hydrolyzed, but the degree of hydrolysis was much lower than in the presence of enzymes; these findings are in accord with the changes in microstructure observed by scanning electron microscopy. The results indicated that the in vitro extent of tofu digestion is related to its hardness, which is in turn related to its microstructure; they also indicated the potential of our developed in vitro dynamic stomach in studying semi-solid foods.

Dietary fiber in bakery products: Source, processing, and function

Bakery products are prevalently consumed foods in the world, and they have been regarded as convenient dietary vehicles for delivering nutritive ingredients into people's diet, of which, dietary fiber (DF) is one of the most popular items. The food industry attempts to produce fiber-enriched bakery products with both increasing nutritional value and appealing palatability. As many new sources of DFs become available, and consumers are moving towards healthier diets, studies of using these DFs as functional ingredients in baked goods are becoming vast. Besides, the nutrition value of DF is commonly accepted, and many investigations have also revealed the health benefits of fiber-enriched bakery products. Thus, this chapter presents an overview of (1) trends in supplementation of DF from various sources, (2) impact of DF on dough processing, quality and physiological functionality of bakery products, and (3) technologies used to improve the compatibility of DF in bakery products.

Functionality of Djulis (Chenopodium formosanum) By-Products and In Vivo Anti-Diabetes Effect in Type 2 Diabetes Mellitus Patients

Simple Summary

According to a report from International Diabetes Federation, in 2020 approximately 463 million adults (20–79 years) were living with diabetes, the principles of medical nutrition therapy are to decrease the risk of diabetes by encouraging healthy food choices and physical activity. Djulis is a unique traditional pseudo-cereal crop native to Taiwan. The hull of djulis, which is usually considered to be agricultural waste, is disposed of in landfills and causes some environmental problems. In recent years, many studies have investigated the functional properties of djulis hull. The focus has been on the byproducts of djulis, a waste utilization approach, to further develop enriched functional foods. Djulis hull contained dietary fibre 75.21 ± 0.17% dry weight, and insoluble dietary fibre (IDF) reached 71.54 ± 0.27% dry weight. The IDF postponed the adsorption of glucose and reduced the activity of α-amylase. We found that it is a good source of valuable ingredients that contain a high amount of dietary fibre. Furthermore, for patients with T2DM, consuming djulis hull 30 and 60 min before a meal significantly reduced blood glucose content as compared with patients at the same postprandial times who did not consume it.

Abstract

Djulis (Chenopodium formosanum Koidz.) is a species of cereal grain native to Taiwan. It is rich in dietary fibre and antioxidants and therefore reputed to relieve constipation, suppress inflammation, and lower blood glucose. The aim of this study was to investigate the composition and physicochemical properties of dietary fibre from djulis hull. Meanwhile, determination of the in vivo antidiabetic effect on patients with type 2 diabetes mellitus (T2DM) after consuming the djulis hull powder. Djulis hull contained dietary fibre 75.21 ± 0.17% dry weight, and insoluble dietary fibre (IDF) reached 71.54 ± 0.27% dry weight. The IDF postponed the adsorption of glucose and reduced the activity of α-amylase. Postprandial blood glucose levels in patients with T2DM showed three different tendencies. First, the area under the glucose curve was significantly lower after ingesting 10 or 5 g djulis hull powder, which then postponed the adsorption of glucose, but the area under the glucose curve was similar with the two doses. After consuming 10 g djulis hull before 75 g glucose 30 and 60 min after the meal, patients with T2DM had blood glucose values that were significantly lower at the same postprandial times than those of patients who did not consume djulis hull. In short, patients who consumed djulis hull prior to glucose administration had decreased blood glucose level compared with those who did not. Djulis hull may have benefits for patients with T2DM.

Effects of soluble dietary fibers on the viscosity property and digestion kinetics of corn starch digesta

Four soluble dietary fibers (SDFs) were fortified with corn starch (CS) at different concentrations to match the same viscosity equivalents. The mixtures were subjected to a simulated digestion procedure to study the effects of SDFs on viscosity properties and digestion kinetics of CS. Results showed that SDFs increased the hydration property and decreased the water mobility of digesta. During digestion process, SDFs increased the apparent viscosity of digesta to some extent, and showed significant difference to delay the decay of digesta viscosity (k_v). The amylolysis inhibitory ability was similar when each SDF was present at the same viscosity equivalent, however, significant differences were found on the digestion rate constant of k₂. Linear correlations between k_v and k₂ were established for 1 and 2 equivalent groups. These results demonstrated that SDFs could delay the digestion process as chemistry differences, which related to their ability on delaying the change of digesta viscosity.

Intake of soluble fibre from chia seed reduces bioaccessibility of lipids, cholesterol and glucose in the dynamic gastrointestinal model simgi®

The role of soluble fibres on hypoglycemic and hypocholesterolemic effects has been widely documented, but the effect on glucose and cholesterol binding capacity of soluble fibre extracted from chia seed mucilage has not been studied until now. In the present research, dynamic gastrointestinal model simgi® combined with absorption static techniques have been used to explore the effect of chia seed mucilage at 0.75 and 0.95% w/w on the bioaccessibility of glucose, dietary lipids and cholesterol along the gastrointestinal tract. Glucose bioaccessibility was reduced when 0.95% of chia mucilage was present in sugar food models. The total reduction of glucose bioaccessibility reached a maximum of 66.7% while glucose dialysis retardation index presented its maximum of 53.4% at the end of small intestine digestion. The in vitro studies with lipid food models, showed that the presence of both, 0.75 and 0.95% of chia seed mucilage caused substantial reductions on the bioaccessibility of free fatty acids (16.8 and 56.1%), cholesterol (18.2 and 37.2% respectively) and bile salts (4.8 and 64.6%), revealing a clear dependence on fibre concentration. These innovative results highlight the potential functionality of the soluble fibre extracted from chia seeds to improve lipid and glycemic profiles and suggest the dietary health benefits of this new soluble fibre source as an ingredient in functional foods designed to reduce the risk of certain non-communicable diseases.

Physical effects of dietary fibre on simulated luminal flow, studied by in vitro dynamic gastrointestinal digestion and fermentation

During the transit through the gastrointestinal tract, fibre undergoes physical changes not usually included in in vitro digestion studies even though they influence nutrient diffusion and might play a role in gut microbiota growth. The aim of this study was to evaluate how physical fibre properties influence the physical properties of gastrointestinal fluids using a gastrointestinal model (stomach, small intestine, ascending colon, transverse colon, and descending colon) (simgi®). Analysis by rheological and particle size characterisation, microbiota composition and short-chain fatty acid (SCFA) determination allows the achievement of this goal. First, the water-holding capacity (WHC), microstructure, and viscosity of eight different fibres plus agar were tested. Based on the results, potato fibre, hydroxypropyl methylcellulose (HPMC), psyllium fibres, and agar (as a control) were selected for addition to a medium growth (GNMF) that was used to feed the stomach/small intestine and colon compartments in the simgi®. During gastrointestinal digestion, GNMF was collected at 5, 30 and 55 minutes of processing at the gastric stage and after the intestinal stage. Then, samples of GNMF with faecal slurry were collected at 0, 24 and 48 h of colonic fermentation. Results showed fibre-dependence on apparent viscosity. Although psyllium was partially broken down in the stomach (decrease in particle size), it was the most viscous at the colonic stage, opposite to the potato fibre, but both led to the highest total SFCA and acetic acid production profile. On a microbiological level, the most relevant increase of bacterial growth was observed in the faecal Lactobacillus species, especially for HPMC and potato fibre, that were not digested until reaching the colon. Besides fibre fermentability, viscosity also influenced microbial growth, and it is necessary to characterise these changes to understand fibre functionality.

Replacing starch in beef emulsion models with β-glucan, microcrystalline cellulose, or a combination of β-glucan and microcrystalline cellulose

Barley sourced beta-glucan (βG), microcrystalline cellulose (MCC), or starch were added to beef emulsions containing beef, olive oil, salts, and water. Emulsions with inclusion levels of 1% of βG, MCC, or starch, 2% of βG, MCC, or starch, or 3% of βG, MCC, or starch, and a mixture of βG (1.5%) and MCC (1.5%) were evaluated for proximate composition, cooking loss, instrumental color, and texture profile analyses (TPA) in three independent replications. As expected, proximate composition differed based mainly on the hydrocolloid used and formulation. Cooking loss was not different among treatments. However, TPA differed with βG samples having lower (P < .05) values for hardness, adhesiveness, cohesiveness, gumminess, and chewiness compared with MCC and starch samples, while samples prepared with MCC and starch presented similar TPA. Emulsions prepared with βG had greater (P < .05) b* values before cooking when compared with emulsions prepared with MCC and starch, but these differences were not observed in cooked emulsions.

Re-evaluation of the mechanisms of dietary fibre and implications for macronutrient bioaccessibility, digestion and postprandial metabolism

The positive effects of dietary fibre on health are now widely recognised; however, our understanding of the mechanisms involved in producing such benefits remains unclear. There are even uncertainties about how dietary fibre in plant foods should be defined and analysed. This review attempts to clarify the confusion regarding the mechanisms of action of dietary fibre and deals with current knowledge on the wide variety of dietary fibre materials, comprising mainly of NSP that are not digested by enzymes of the gastrointestinal (GI) tract. These non-digestible materials range from intact cell walls of plant tissues to individual polysaccharide solutions often used in mechanistic studies. We discuss how the structure and properties of fibre are affected during food processing and how this can impact on nutrient digestibility. Dietary fibre can have multiple effects on GI function, including GI transit time and increased digesta viscosity, thereby affecting flow and mixing behaviour. Moreover, cell wall encapsulation influences macronutrient digestibility through limited access to digestive enzymes and/or substrate and product release. Moreover, encapsulation of starch can limit the extent of gelatinisation during hydrothermal processing of plant foods. Emphasis is placed on the effects of diverse forms of fibre on rates and extents of starch and lipid digestion, and how it is important that a better understanding of such interactions with respect to the physiology and biochemistry of digestion is needed. In conclusion, we point to areas of further investigation that are expected to contribute to realisation of the full potential of dietary fibre on health and well-being of humans.

Beneficial health characteristics of native and hydrolysed konjac (Amorphophallus konjac) glucomannan

The impact of ingesting glucomannans on health is not limited to colonic-focused fermentation into short-chain fatty acids (SCFAs), which might have some local health benefits; it also helps in treating disease states and enhancing the body's immune system, both within the gut and in/on other parts of the body. The local and systemic roles of hydrolysed glucomannans, especially konjac glucomannans, in the mouth, oesophagus, stomach, small intestine, large intestine, gut-associated lymphoid tissue (GALT), skin and vagina, are highlighted. Therapeutic applications are discussed. © 2015 Society of Chemical Industry.