Distinct Characteristics of Rye and Wheat Breads Impact on Their in Vitro Gastric Disintegration and in Vivo Glucose and Insulin Responses

Disintegration of rye and wheat breads during in vitro gastric digestion and its relation to the postprandial glucose and insulin responses of the breads was studied. Breads with distinct composition and texture characteristics were prepared with refined or wholegrain wheat and rye flour by using either straight dough or sourdough process. After chewing and gastric digestion in vitro, 100% wholemeal and refined rye breads prepared by sourdough method were disintegrated to a much lower extent than the wheat breads, having more bread digesta particles with size over 2 or 3 mm. Microstructure of the digesta particles of rye sourdough bread revealed more aggregated and less degraded starch granules when compared to refined wheat bread. The postprandial insulin responses, but not those of glucose, to the 100% rye breads made with sourdough method were lower than the responses to the refined wheat bread. Addition of gluten or bran in rye sourdough bread increased insulin response. PCA (Principal Component Analysis) analysis confirmed that the insulin response had a negative correlation with the number of larger particles after in vitro digestion as well as amount of soluble fiber and sourdough process. Since the high relative proportion of large sized particles after chewing and in vitro gastric digestion was associated with low postprandial insulin responses, the analysis of structural disintegration in vitro is proposed as a complementary tool in predicting postprandial physiology.Peer reviewe

Biochemical characterization and technofunctional properties of bioprocessed wheat bran protein isolates

The effect of three combinations of bioprocessing methods by lactic acid fermentation, cell wall hydrolyzing enzymes and phytase on the biochemical (protein, fat, carbohydrate composition) and technofunctional properties (protein solubility, emulsifying and foaming properties) of wheat bran protein isolates were evaluated. The bioprocessing increased the protein (up to 80%) and fat content (up to 22.8%) in the isolates due to the degradation of starch and soluble pentosans. Additional proteins, globulin 3A and 3C, chitinase, beta-amylase and LMW glutenins, were identified from the electrophoretic pattern of the protein isolate bioprocessed with added enzymes. Generally, the bioprocessed protein isolate had lower protein solubility and stronger net charge in pH below 7, when compared to the protein isolate made without bioprocessing. The emulsifying properties of the protein isolates were not affected by bioprocessing. However, the foaming stability of the protein isolates was nearly doubled by bioprocessing with cell wall hydrolyzing enzymes and phytase.Peer reviewe

Influence of oat flour characteristics on the physicochemical properties of oat-based milk substitutes

This study aimed at investigating the effect of oat composition on the quality characteristics of oat-based milk substitute (OBMS). Raw materials for OBMS consisted of thirty pure cultivar oat flours produced by industrial milling process. The main steps in OBMS preparation included mixing of 10% oat flour with water, starch hydrolysis, solid-liquid separation and formulation of the final product. OBMS was characterised in terms of mass and protein yields, protein content, reducing sugars, particle size, viscosity, dispersion stability and colour. The different composition of oat flours affected the characteristics of the OBMS in terms of mass yield (81.3–88.1%), dry matter yield (56.7–73.8%), protein content (0.63–1.10%), protein yield (31.4–61.6%), content of free reducing sugars (13.1–19.1%), and physical properties including particle size, dispersion stability and viscosity. OBMS mass and dry matter yields correlated positively with both total and damaged starch contents of the oat flour as well as the share of damaged starch of the total starch of the sample, while flour starch content correlated negatively with protein content of OBMS. Protein content of the flour correlated negatively with the mass, dry matter and protein yields and positively with protein content of OBMS. All colour values (L*, a*, b*) of the flour correlated with colour value b* of the OBMS. Protein content and viscosity of OBMS correlated positively with dispersion stability of OBSM. In conclusion, the clear relation between oat composition and the final properties of OBMS suggest relevance of selecting specific oat raw materials to produce good quality OBMS

Influence of oat flour characteristics on the physicochemical properties of oat-based milk substitutes

This study aimed at investigating the effect of oat composition on the quality characteristics of oat-based milk substitute (OBMS). Raw materials for OBMS consisted of thirty pure cultivar oat flours produced by industrial milling process. The main steps in OBMS preparation included mixing of 10% oat flour with water, starch hydrolysis, solid-liquid separation and formulation of the final product. OBMS was characterised in terms of mass and protein yields, protein content, reducing sugars, particle size, viscosity, dispersion stability and colour. The different composition of oat flours affected the characteristics of the OBMS in terms of mass yield (81.3–88.1%), dry matter yield (56.7–73.8%), protein content (0.63–1.10%), protein yield (31.4–61.6%), content of free reducing sugars (13.1–19.1%), and physical properties including particle size, dispersion stability and viscosity. OBMS mass and dry matter yields correlated positively with both total and damaged starch contents of the oat flour as well as the share of damaged starch of the total starch of the sample, while flour starch content correlated negatively with protein content of OBMS. Protein content of the flour correlated negatively with the mass, dry matter and protein yields and positively with protein content of OBMS. All colour values (L*, a*, b*) of the flour correlated with colour value b* of the OBMS. Protein content and viscosity of OBMS correlated positively with dispersion stability of OBSM. In conclusion, the clear relation between oat composition and the final properties of OBMS suggest relevance of selecting specific oat raw materials to produce good quality OBMS

Variability of carbohydrate composition and pasting properties of oat flakes and oat flours produced by industrial oat milling process – Comparison to non-heat-treated oat flours

This study characterised the starch and dietary fibre properties and their significance to the pasting characteristics of oat flakes and flours produced from 30 Finnish pure cultivar oats with or without the industrial scale milling process. Large variation in carbohydrate characteristics was observed, the insoluble dietary fibre content of flours was 2.4–5.7 % and soluble dietary fibre was 4.9–8.0 %. The oat milling process induced a significant amount of starch damage (p < 0.05), a fourfold increase from 1 % to 4 % in average was observed. The pasting properties of both flakes and flours were interlinked (p < 0.05) with the chemical composition of oats, i.e., high starch content of flours was connected to higher paste viscosity values. The milling process increased the peak, trough, setback, final and time to peak viscosities of oat flours. These results show the significance of oat milling process, including kilning, to the carbohydrate quality of oats

Impact of Enzymatic Hydrolysis and Microfluidization on the Techno-Functionality of Oat Bran in Suspension and Acid Milk Gel Models

Oat bran is a nutritionally rich ingredient, but it is underutilized in semi-moist and liquid foods due to technological issues such as high viscosity and sliminess. The aim of this work was to improve the technological properties of oat bran concentrate (OBC) in high-moisture food applications by enzymatic and mechanical treatments. OBC was hydrolyzed with β-glucanase (OBC-Hyd) and the water-soluble fraction (OBC-Sol) was separated. OBC, OBC-Hyd and OBC-Sol were further microfluidized at 5% dry matter content. Enzymatic treatment and microfluidization of OBC reduced the molecular weight (Mw) of β-glucan from 2748 kDa to 893 and 350 kDa, respectively, as well as the average particle size of OBC (3.4 and 35 times, respectively). Both treatments increased the extractability of the soluble compounds from the OBC samples (up to 80%) and affected their water retention capacity. OBC in suspension had very high viscosity (969 mPa·s) when heated, which decreased after both enzyme and microfluidization treatments. The colloidal stability of the OBC in suspension was improved, especially after microfluidization. The addition of OBC samples to acid milk gels decreased syneresis, improved the water holding capacity and softened the texture. The changes in the suspension and gel characteristics were linked with reduced β-glucan Mw and OBC particle size