Hypolipidemic study of xylanase-modified corn bran fibre in rats

In order to understand the regulatory effect of xylanase-modified corn bran fibre (XMF) on lipid homeostasis, detailed influences, following the ingestion of XMF and its original form (corn bran dietary fibre, CDF), on serum, liver and faecal lipids were studied in Sprague–Dawley rats. In both CDF and XMF groups, serum total cholesterol (TC), triacylglycerol (TG) and low-density lipoprotein cholesterol (LDL-C) were significantly lowered after 4 weeks (p < 0.05). By the end of week 6, data in the XMF group showed that serum LDL-C was lowered further and high-density lipoprotein cholesterol (HDL-C) was significantly increased (p < 0.05); liver TC, TG and fat were significantly lower (p < 0.05), while the excretions of faecal fat, TC and bile acids were significantly higher (p < 0.05). The decrease of liver and serum lipids in the XMF group was consistent with the improved excretion of faecal lipids and bile acids. Other related mechanisms are also considered.     

Treatment of corn bran dietary fiber with xylanase increases its ability to bind bile salts,in vitro

A corn bran fiber (CDF) was further treated by xylanase and the product – XMF was obtained. Response surface methodology (RSM) was used to optimize the hydrolysis conditions (pH, time and enzyme dosage), binding of cholate (B_SC), chenodeoxycholate (B_SCDC), deoxycholate (B_SDC) and taurocholate (B_STC) by XMF were determined. The influence trends of 3 factors were dissimilar, pH affected the binding capacity most significantly, then hydrolysis time, lastly the dosage. The optimized conditions were pH 5.3, 1.75 h and enzyme dosage 0.70 g/100 g CDF, the values for B_SC, B_SCDC, B_SDC and B_STC were increased to 1.88, 2.34, 1.67 and 2.08 fold of CDF, respectively, which were not significantly different from those predicted (p < 0.05). There was not correlation between the bindings of any two bile salts by XMF, which indicates that the binding mechanisms of different bile salts by XMF studied here are different. The TDF, IDF and SDF content of XMF were increased by 12%, 12% and 285%, respectively. The WHC, SW and OBC of XMF were 1.11, 1.34 and 1.87 fold of CDF, respectively.     

Effects of enzymatic treatment conditions on dietary fibre content of wheat bran and use of cellulase-treated bran in cookie

A commercial cellulase preparation (Viscozyme Cassava C) was employed to process wheat bran to improve the ratio of insoluble to soluble dietary fibre. The effects of initial moisture content, enzyme dosage, and incubation time on the content of soluble and insoluble fibre during the enzymatic treatment were investigated. The appropriate conditions for the cellulase treatment were initial moisture content of 0.75 g water g⁻¹ dry matter, enzyme dosage of 9 U g⁻¹ dry matter and incubation time of 120 min under which the ratio of insoluble to soluble fibre of wheat bran was lowered by 42%. Untreated and cellulase-treated wheat bran was incorporated into cookies at levels of 0%, 20%, 30%, 40% and 50%. Cookie with 50% cellulase-treated bran showed 21% lower ratio of insoluble to soluble fibre as well as 14% lower hardness and 13% higher overall acceptability than sample with the same amount of untreated bran.     

羧甲基化法制备高持水力麦麸膳食纤维研究

以不溶性麦麸膳食纤维为原料,持水力为指标,对羧甲基化法制备高持水力麦麸膳食纤维进行了研究。根据单因素试验结果,利用响应面对碱化时间、乙醇体积分数、反应温度和反应时间进行了优化,确定羧甲基化改性麦麸膳食纤维的最佳工艺条件为氢氧化钠浓度为3.38 mol/L,碱化温度35℃,碱化时间56min,乙醇体积分数87%,醚化温度53℃,醚化时间3.3 h,在此条件下改性产品的得率为113.87%,改性产品的取代度为0.293 9;产品持水力为11.825 g/g,与改性前相比,产品持水力提高了105.79%。     

接枝化改性对麦麸膳食纤维持水力影响的研究

以不溶性麦麸膳食纤维为原料,持水力为指标,采用丙烯酸接枝化对麦麸膳食纤维进行改性。通过单因素及响应面优化实验,确定了丙烯酸接枝化改性麦麸膳食纤维的最佳工艺条件:麦麸膳食纤维原料8.000g,液料比(m/m)10.4,引发时间1.0h,引发剂用量0.150g,丙烯酸8.5mL,反应温度87℃,接枝时间2.6h,此条件下产品得率为89.01%,持水力达9.648g/g,与原料相比,提高了67.90%。      

Effects of dietary broccoli fibre and corn oil on serum lipids, faecal bile acid excretion and hepatic gene expression in rats

To determine the effects of broccoli fibre and corn oil on lipid metabolism, male Sprague-Dawley rats were fed diets containing high (30%) or low (5%) corn oil, in combination with either 7.5% broccoli fibre or cellulose, for 4 months. High corn oil groups had significantly lower serum cholesterol and triglycerides than had low corn oil groups (p < 0.001). Broccoli fibre also lowered serum cholesterol and triglyceride levels compared to cellulose fibre. Faecal bile acid concentrations were higher in high corn oil-fed rats than in low corn oil-fed rats, with broccoli fibre inclusion in high corn oil diets resulting in higher faecal bile acid concentrations. Regardless of corn oil level, broccoli fibre supplementation in the diet resulted in an increase (p = 0.018) in hepatic cytochrome P450, family 7A1 (CYP7A1) expression. High corn oil feeding resulted in reduced expression of fatty acid synthase (FAS) and increased expression of carnitine palmitoyl transferase 1a (CPT1a) and 3-hydroxy-3-methyl-coenzyme A reductase (HMGCR) (p < 0.05). Our findings suggest that high dietary corn oil and broccoli fibre have beneficial effects on lipid metabolism. Corn oil lipid-lowering effects may be due to alteration of hepatic expression of genes involved in lipid synthesis and increased rate of cholesterol catabolism to bile acids. Broccoli fibre may also act via its physical properties to reduce enterohepatic bile acid recycling and intestinal lipid absorption, and increase luminal binding of bile acids, resulting in increased faecal bile acid excretion.     

Effect of wheat bran dietary fibre on the rheological properties of dough during fermentation and Chinese steamed bread quality

The effects of wheat bran dietary fibre (WBDF) on the rheological properties of dough during fermentation and quality of Chinese steamed bun (CSB) were investigated. The study revealed that with the increase of the content of WBDF, the dough extensibility and time at which gas starts to escape from the dough significantly decreased but the dough firmness significantly increased (P < 0.05). The elastic modulus and viscous modulus showed an upward trend, probably due to the increased molecular weight of the viscoelastic body resulting from the presence of WBDF. Additionally, by changing the quality of the gluten network, the specific volume and L^* value significantly decreased from 2.52 to 1.31 mL g⁻¹, and from 87 to 51, respectively, these adverse effects on CSBs could be moderated by the fermentation process.     

A comparative study on the structural and functional properties of water-soluble and alkali-soluble dietary fibres from rice bran after hot-water,ultrasound, hydrolysis by cellulase,and combined pre-treatments

The aim of the study was to estimate the optimum method to obtain water-soluble (WS-DF) and alkali-soluble (AS-DF) dietary fibres fibres from defatted rice bran (DRB) to develop functional components for food. The different pre-treatments of DRB, such as ultrasound (US) treatment, hydrolysis by cellulase (HC) and combined treatment (HC-US), were compared with hot-water (HWT) treatment on yields, and structural, physicochemical, and functional properties of WS-DF and AS-DF. Results showed that amounts of WS-DF (5.54–9.03 g/100 g) and AS-DF (7.22–9.58 g/100 g), and total dietary fibre (TDF) (42.21–45.44 g/100 g) obtained from the DRB after US, HC and HC-US treatments were significantly higher than that after HWT (6.36, 5.65 and 31.92 g/100 g, respectively). The FT-IR indicated that the effect of applied treatments on the changes of the chemical structure of polysaccharides was stronger for the WS-DF than that for the AS-DF. Scanning electron microscopy (SEM) showed that the surfaces of US-treated DFs particles were much more fractured than those after the HWT and HC. The combined HC-US treatment at 50°C for 30 min significantly enhanced the purity (85–91%) and homogeneity of RB DFs structure resulting in increased water-holding, swelling and glucose adsorption capacities compared to conventional processes maintaining acceptable bioactivity. Our study showed that conventional hot water extraction could be replaced with the ultrasonication technology as an effective tool for the modification of rice bran DFs’ structure and functional properties.     

Processing of rye bran influences both the fermentation of dietary fibre and the bioconversion of lignans by human faecal flora in vitro

Plant lignans are converted to mammalian forms, enterodiol and enterolactone, in the colon. Enhanced plasma or urinary enterolactone levels have been associated with lowered risk of cardiovascular diseases and breast cancer. Processed rye bran and its fractions were compared to ascertain the fermentation rates of fermentable carbohydrates and the bioconversion of lignans. Rye bran was extruded and treated with a food‐grade xylanase. Part of the xylanase‐treated rye bran was separated into a soluble rye bran extract and an insoluble residue, and a part of the xylanase‐treated rye bran was freeze‐dried without separation. All the samples were digested by pepsin and pancreatin and subsequently fermented with a human faecal inoculum in vitro. The consumption of carbohydrates, the productions of short‐chain fatty acids (SCFA), enterodiol and enterolactone were followed as a function of time. The soluble rye bran extract showed the fastest fermentation rate and the highest extent of fermentation determined as the consumption of neutral sugar residues (arabinose, xylose and glucose), the production of SCFA and the formation of enterodiol and enterolactone. Xylanase treatment enhanced the fermentation rate of extruded rye bran. An even a higher fermentation rate was observed for rye bran extract containing soluble carbohydrates. The amount of enterolactone precursors in rye seemed to be too low for enterolactone formation using an amount of substrate suitable for carbohydrate fermentation. However, xylanase treatment enhanced the availability of plant lignans from rye bran, as enterodiol formation was increased by the use of xylanase. Copyright © 2005 Society of Chemical Industry     

Short‐chain fatty acid content in the hindgut of rats fed various composite foods and commercial dietary fibre fractions from similar sources

The fermentability of indigestible carbohydrates and content of short‐chain fatty acids along the hindgut of rats were investigated using plant materials of importance in the Swedish diet (instant potato powder, apples and oat flakes). Results with the composite food products were compared with commercial fibre fractions obtained from similar sources, ie potato fibre, apple pectin and β‐glucan‐enriched oat fibre. The materials were incorporated into diets yielding a concentration of 60 or 70 g kg^?1 indigestible carbohydrates. The fermentability of indigestible carbohydrates was high with all diets, between 79 and 90%. All substrates except the pure apple pectin generated intermediate to high proportions of butyric acid in the caecum (15–22 vs 8%). The potato products gave high concentrations of butyric acid in the distal colon. The potato powder, ie the diet with the highest content of resistant starch (22 g kg^?1), also gave the highest proportion of butyric acid in the distal colon (19%), which was higher than the proportion in the caecum with the same substrate (15%) (P < 0.005). The composite foods promoted a higher proportion of butyric acid in the distal colon as compared with the commercial fibre fractions (P < 0.05). © 2002 Society of Chemical Industry     

Effect of grape antioxidant dietary fibre on the prevention of lipid oxidation in minced fish: Evaluation by different methodologies

The effect of grape antioxidant dietary fibre (GADF) addition to minced fish muscle (MFM) on lipid stability during frozen storage (6 months) was studied. Concentrations of 0%, 2%, and 4% GADF were added to MFM samples. Analyses were carried out immediately after preparation of samples and during and after storage at −20 °C. GADF was characterized in terms of dietary fibre, total polyphenols and antioxidant capacity, and multifunctional antioxidant assays were carried out on all the MFM samples. The addition of red grape fibre considerably delayed lipid oxidation in minced horse mackerel muscle during the first 3 months of frozen storage.     

Effects of dietary l-carnitine supplementation on the response to an inflammatory challenge in mid-lactating dairy cows: Hepatic mRNA abundance of genes involved in fatty acid metabolism

This study aimed at characterizing the effects of dietary l-carnitine supplementation on hepatic fatty acid (FA) metabolism during inflammation in mid-lactating cows. Fifty-three pluriparous Holstein dairy cows were randomly assigned to either a control (CON, n = 26) or an l-carnitine supplemented (CAR; n = 27) group. The CAR cows received 125 g of a rumen-protected l-carnitine product per cow per day (corresponding to 25 g of l-carnitine/cow per day) from d 42 antepartum (AP) until the end of the trial on d 126 postpartum (PP). Aside from the supplementation, the same basal diets were fed in the dry period and during lactation to all cows. In mid lactation, each cow was immune-challenged by a single intravenous injection of 0.5 μg of LPS/kg of BW at d 111 PP. Blood samples were collected before and after LPS administration. The mRNA abundance of in total 39 genes related to FA metabolism was assessed in liver biopsies taken at d −11, 1, and 14 relative to LPS (d 111 PP) and also on d 42 AP as an individual covariate using microfluidics integrated fluidic circuit chips (96.96 dynamic arrays). In addition to the concentrations of 3 selected proteins related to FA metabolism, acetyl-CoA carboxylase α (ACACA), 5′ AMP-activated protein kinase (AMPK), and solute carrier family 25 member 20 (SLC25A20) were assessed by a capillary Western blot method in liver biopsies from d −11 and 1 relative to LPS from 11 cows each of CAR and CON. On d −11 relative to LPS, differences between the mRNA abundance in CON and CAR were limited to acyl-CoA dehydrogenase (ACAD) very-long-chain (ACADVL) with greater mRNA abundance in the CAR than in the CON group. The liver fat content decreased from d −11 to d 1 relative to the LPS injection and remained at the lower level until d 14 in both groups. One day after the LPS challenge, lower mRNA abundance of carnitine palmitoyltransferase 1 (CPT1), CPT2, ACADVL, ACAD short-chain (ACADS), and solute carrier family 22 member 5 (SLC22A5) were observed in the CAR group as compared with the CON group. However, the mRNA abundance of protein kinase AMP-activated noncatalytic subunit gamma 1 (PRKAG1), ACAD medium-chain (ACADM), ACACA, and FA binding protein 1 (FABP1) were greater in the CAR group than in the CON group on d 1 relative to LPS. Two weeks after the LPS challenge, differences between the groups were no longer detectable. The altered mRNA abundance before and 1 d after LPS pointed to increased transport of FA into hepatic mitochondria during systemic inflammation in both groups. The protein abundance of AMPK was lower in CAR than in CON before the LPS administration. The protein abundance of SLC25A20 was neither changing with time nor treatment and the ACACA protein abundance was only affected by time. In conclusion, l-carnitine supplementation temporally altered the hepatic mRNA abundance of some genes related to mitochondrial biogenesis and very-low-density lipoprotein export in response to an inflammatory challenge, but with largely lacking effects before and 2 wk after LPS.