Influence of microwave roasting on chemical composition, oxidative stability and fatty acid composition of flaxseed (Linum usitatissimum L.) oil.

In this study, flaxseeds roasted at microwave (MW) powers of 180, 360 and 540 W for 5 and 10 min were evaluated for their influence on oil yield, chemical properties, carotenoid and chlorophyll contents, total phenolic content (TPC), radical scavenging activity (RSA), oxidative stability index (OSI), fatty acid composition and Maillard reaction products (MRPs). MW roasting at 540 W for 10 min significantly increased the oil yield, TPC, OSI, RSA, a* value, browning index, carotenoid and chlorophyll contents while decreased the L* and b* values of flaxseed oil (FSO). MRPs were detected only in oil of flaxseeds roasted at 540 W for 10 min. The level of stearic, palmitic, oleic, linoleic and α-linolenic acids were slightly changed and FTIR spectra showed minor variation in peak intensities of oils from different MW roasted flaxseeds. MW roasting (540 W for 10 min) is recommended for improving quality and stability characteristics of FSO.

Proximate composition, amino acid profile, pasting and process characteristics of flour from different Tartary buckwheat varieties.

Flour from twenty-three Tartary buckwheat varieties were evaluated and compared for proximate composition, mineral and amino acid profile. Further, pasting properties and process characteristics such as foaming, oil and water absorption capacities, emulsification properties were determined for identifying the efficient application of Tartary buckwheat in food systems. Ash, protein and fat contents of the flours ranged between 1.76-2.80%, 9.06-14.88%, and 2.02-3.60%, respectively. Buckwheat flours from all varieties had abundant K, Mg and Ca content, with the highest in B-121, IC-329200 and IC-274439, respectively. All essential amino acids were detected in all varieties with leucine present in abundance. Isoleucine, cystine and asparagine were limiting. Emulsifying and foaming properties of all buckwheat flours improved as the pH increased from 4 to 10. Emulsion activity index (pH 10) showed a significant positive correlation with hydrophobic amino acids. Flours from most of the buckwheat varieties had unique pasting properties with very low set back and breakdown viscosities indicating paste stability and lower retrogradation tendency, making them suitable for thickening of sauces and soups.

Impact of infrared and dry air roasting on the oxidative stability, fatty acid composition, Maillard reaction products and other chemical properties of black cumin (Nigella sativa L.) seed oil.

Black cumin seed (BCS) is a novel oil source with potential health benefits. This study investigates the influence of infrared (IR) and dry air (DA) roasting (140, 160 and 180 °C for 5 and 10 min) on BCS oil quality characteristics. Results revealed that the oxidative stability index (OSI), Maillard reaction products (MRPs), chlorophyll and carotenoid contents were increased while acid value (AV), peroxide value (PV) and color values were decreased in DA roasted (180°C for 10 min) BCS oil compared to other DA and IR treatments. DA and IR roasting slightly influenced the fatty acid composition (FAC) of BCS oils. FTIR spectra showed minor changes in peak intensities (at 2854, 2929 and 3008 cm-1) of DA and IR roasted BCS oils. DA roasting proved more effective than IR roasting. The oil from the DA roasted BCS at 180°C for 10 min had significantly higher oil quality and oxidative stability.

Effect of infrared roasting on antioxidant activity, phenolic composition and Maillard reaction products of Tartary buckwheat varieties.

The effect of infrared roasting (130, 150 and 170 °C for 10 min) on antioxidant activity, total phenolic content (TPC), total flavonoid content (TFC), Maillard reaction products (MRP) and phenolic profile in eight Tartary buckwheat (Fagopyrum tataricum) varieties were investigated. TFC (23.74-28.67 mg RE/g) remained unchanged at 130 °C and 150 °C but exhibited a sharp decline at 170 °C. TPC (8.90-14.72 mg GAE/g) and TAA (11.37-12.74 µmol TE/g) decreased significantly with increase in roasting temperature. The lowest fluorescence of advanced MRP (FAST) index was observed for buckwheat roasted at 130 °C (230.76-338.55%) and the highest at 170 °C (420.30-523.72%). IC-341651 and IC-107994 had high antioxidant properties and SMLBW-4 exhibited lowest browning index (BI), free fluorescent intermediate compounds (FIC) and FAST index, indicating the least MRP formation. Gallic acid and quercetin were detected in only bound and free-form, respectively. Rutin was the most thermostable polyphenol detected in all buckwheat varieties.

Rheology and microstructure of gels based on wheat arabinoxylans enzymatically modified in arabinose to xylose ratio.

BACKGROUND: Arabinoxylans (AX) are polysaccharides consisting of a backbone of xyloses with arabinose substituents ester-linked to ferulic acid (FA). The arabinose to xylose ratio (A/X) in AX may vary from 0.3 to 1.1. AX form covalent gels by cross-linking of FA but physical interactions between AX chains also contribute to the network formation. The present study aimed to investigate the rheological and microstructural characteristics of gels based on AX enzymatically modified in A/X. RESULTS: Tailored AX presented A/X ranging from 0.68 to 0.51 and formed covalent gels. Dimers of FA content and elasticity (G') increased from 0.31 to 0.39 g kg-1 AX and from 106 to 164 Pa when the A/X in the polysaccharide decreased from 0.68 to 0.51. Atomic force microscopy images of AX gels showed a sponge-like microstructure at A/X = 0.68, whereas, at lower values, gels presented a more compact microstructure. Scanning electron microscopy analysis of AX gels show an arrangement of different morphology, passing from an imperfect honeycomb (A/X = 0.68) to a flake-like microstructure (A/X = 0.51). CONCLUSION: Lower A/X values favor the aggregation of AX chains resulting in an increase in di-FA content, which improves the rheological and microstructural characteristics of the gel formed. © 2017 Society of Chemical Industry.

Suppression of Psyllium Husk Suspension Viscosity by Addition of Water Soluble Polysaccharides.

Psyllium seed husk is an insoluble dietary fiber with many health benefits. It can absorb many times its weight in water, forming very viscous suspensions, which have low palatability and consumer acceptance. We report here a novel approach for decreasing its viscosity, involving inclusion of a soluble polysaccharide in the suspension. This leads to a drastic decrease (up to 87%) in viscosity of suspensions, while maintaining the same dosage level of psyllium and also delivering a significant amount of soluble dietary fiber such as corn bio-fiber gum in a single serving. Four soluble polysaccharides with a range of molecular weights and solution viscosities have been studied for their viscosity suppression effect. Besides improving palatability, another advantage of this approach is that it makes it possible to deliver 2 different dietary fibers in significant quantities, thus offering even greater health benefits.

Isolation of barley hulls and straw constituents and study of emulsifying properties of their arabinoxylans.

Both barley hulls and straw contain valuable arabinoxylans and other useful carbohydrate and non-carbohydrate components. The functional water soluble non-caloric arabinoxylan (hemicellulose B) fraction was isolated from hot water-extracted and de-starched barley hulls and straws by an alkaline hydrogen peroxide extraction followed by ethanol precipitation. Barley hulls contained comparatively more Hemi. B (20.51%) than barley straws (7.41 to 12.94%). The sugar composition of Hemi. B showed that they were typical arabinoxylans containing (in addition to arabinose and xylose) some galactose, glucose and acidic sugars in the side chains. The hemicellulose B fractions from barley straws were superior oil-in-water emulsifiers than those from barley hulls. These Hemi. B fractions contain protein, which contributes to their emulsions stabilizing property.

Physico-chemical characterization of protein-associated polysaccharides extracted from sugar beet pulp.

We have solubilized and separated polysaccharides from sugar beet pulp (SBP) into three fractions with steam assisted flash extraction (SAFE). For pectin, recovery ranged from 8 to 14%, degree of methy-esterification 66-73%, crude protein 1.3-1.7%, M(w) 262-318 kDa, η(w) 0.22-0.23 dL/g, Rg(z) 36-39 nm and Rh(z) 41-42 nm. For alkaline soluble polysaccharides, (ASP I) recovery ranged from 4.0 to 6.5%, crude protein 1.2-4.8%, weight average molar mass (M(w)) 66-68 kDa, weight average intrinsic viscosity (η(w)) 0.27-0.30 dL/g, z-average radius of gyration (Rg(z)) 25-29 nm and z-average hydrated radius (Rh(z)) 10-11 nm. ASP II recovery ranged from 2.0 to 8.6%, crude protein 1.2-4.8%, M(w) 299-339 kDa, η(w) 0.22-0.33 dL/g, Rg(z) 33-34 nm and Rh(z) 30-34 nm. Recovery of the residue mainly cellulose, ranged from 20.3 to 22.3%. The cellulose in this fraction was converted to carboxymethyl cellulose (CMC). The CMC fraction contained 0.33-0.43 crude protein and had an M(w) ranging from 127 to 263 kDa, η(w) 3.6-8.0 dL/g, Rg(z) 35-45 nm and Rh(z) 27-40 nm.