Effects of extrusion process variables on the physical properties of oat containing extrudates

Oats are a good source of protein and dietary fibre, especially β-glucan. Due to the health benefits of β-glucan, oats have gained popularity in snack food formulations. The literature review deals with oats and its components, removal of lipids and fractionation of oat products. The particular emphasis of the literature review was given to studies on the effects of different oat fractions and extrusion process variables on the properties of oat-containing extrudates. The aim of this study was to find out how different oat fractions and extrusion process variables (screw speed, water content and feed rate) affect the physical and chemical properties of the extrudates. The measured physical properties were expansion, hardness and water content. Extrusion trials were carried out by using defatted oat endosperm flour (EF) as the main ingredient. Whole grain oat flour (WF) was used as a reference. To improve the nutritional quality, defatted oat protein concentrate (PC) and defatted oat bran concentrate (OBC) were added to EF. The oat fractions were defatted by supercritical carbon dioxide (SC-CO2). Pregelatinised corn starch (CS) and waxy corn starch (WS) were added in some trials to increase the expansion of the extrudates. A co-rotating twin-screw extruder was used for the extrusion. Different process variables were: water content of the mass (16, 18 and 20%), screw speed (240, 370 and 500 rpm) and feed rate (68, 76 and 84 g/min). The temperature profile of the extruder barrel was held constant in all of the trials: 40, 70, 70, 100, 110, 130 and 130 °C (sections 1–6 and die). Screw speed had significant effect on the expansion and hardness. Expansion increased and hardness decreased with increasing screw speed. Water content of the mass affected all the response variables in WF extrudates and all but not hardness and torque in EF extrudates. Increased water content of mass decreased the expansion and hardness in WF extrudates. Feed rate did not have significant effect on the physical properties. When using EF, more expanded and less hard extrudates compared to the WF were obtained. Addition of PC or OBC (10%) decreased the expansion and increased the hardness. Mixing of EF with corn starch (CS or WS; 30%) gave less hard and more expanded extrudates compared to pure EF. The highest expansion was achieved by the addition of WS. Even addition of OBC (20%) in a presence of WS (30%) gave highly expanded and less hard extrudates with high β-glucan content 7.4% (dry weight). Decreasing the particle size of OBC (by ultra-fine milling) or the molecular weight of β-glucan (by enzymatic hydrolysis) did not affect the physical properties of the extrudates even though small decrease in hardness was observed in the trial with enzyme-hydrolysed OBC. The results showed that defatted oat fractions can successfully be used in extrusion when mixed with corn starch. Screw speed had the most profound effect on the physical properties of the oat-containing extrudates followed by the water content of mass

Nondestructive Imaging of Cellular Solid Foods

The successful use of XMT in other fields of science (e.g., medical, agricultural, biological and material science) has led its further application in food structure characterization. Cellular solid structures have great impact on sensory properties and associated with also textural-mechanical properties. XMT is able to present rigorous quantitative information related to cellular architecture of solid foods such as cell size and distribution, cell wall thickness, cell connectedness and porosity both in 2D and 3D. The accurate microstructural characterization of cellular solid foods would also help food engineers and scientists to understand and develop links between structure–mechanical–sensory properties. Based on these and the use of numerical simulation technologies together with modelling approaches can be used to design novel food structures and textures. Furthermore, the noninvasive XMT technology does not require tedious sample preparation methods compared to other microscopy technologies such as light microscopy or confocal scanning light microscopy. The continuous development in data processing and equipment manufacturing technologies will enable the use of XMT technology for in-line or on-line food structure analysis during processing.Peer reviewe

Effects of structural and textural properties of brittle cereal foams on mechanisms of oral breakdown and in vitro starch digestibility

This study was jointly funded by the Academy of Finland (Academy Professorship, Kaisa Poutanen - grant number 131460) and by the Raisio Plc's Research Foundation (personal grant to Syed Ariful Alam, grant decisions of 2016).Structural and textural properties as well as the dietary fibre content of solid cereal foams influence the oral breakdown of structure, bolus formation and digestibility. The aimof this studywas to investigate howstructural differences of solid cereal foams (puffs vs. flakes) affect in vivo chewing and in vitro starch digestion. Four extruded puffs and flakes were produced from endosperm rye flour by extrusion processing without or with 10% rye bran (RB) addition. Extruded puffs and flakes were masticated by fifteen healthy females and the process was monitored using electromyography. Extruded puffs were more porous than flakes (97% vs 35%). The two productswere also significantly different (p b 0.05) in their structural and textural properties such as expansion, hardness, density and crispiness. A negative correlation was observed between hardness and crispiness index (p b 0.05, r=−0.950) and density and porosity (p b 0.05, r=−0.964). Addition of 10% RB had a significant effect on structural, textural and mastication properties both for puffs and flakes. Mastication of puffs required less total work than flakes (204 vs. 456%) and theywere degraded to smaller particles than flakes during mastication. Irrespectively of the considerable differences in structure, texture and oral disintegration process, no significant (p b 0.05) differenceswere observed between puffs and flakes (86.4 vs. 85.1) in terms of starch hydrolysis index. RB addition increased the hydrolysis index of puffs and flakes to 89.7 and 94.5, respectively, which was probably attributable to the increased number of particles in the bolus.Peer reviewe

Marketing System of Shrimp in Some Selected Areas of Bangladesh

A study was undertaken to examine the marketing system value chin analysis of shrimp in selected areas of Khulna district of Bangladesh during the month of March-April 2012. The objectives of the study were to estimate costs and margins, seasonal price variation and to test market integration of shrimp. Primary were used for this study. The higher marketing cost was incurred by aratdars and the lowest by retailer. On the other hand, retailers earned the highest net marketing margins.T he findings of the study revealed that the marketing of shrimp was a profitable business and some recommendations were provided for the improvement of shrimp marketing in the country. Keywords: Engle Granger co-integration, Market integration, marketing system, price behavio

Analysis of Marketing Efficiency, Value Addition and Spatial Co-Integration of Mozambique Tilapia (Oreochromis mossambicus) Fish in Some Selected Areas of Bangladesh

A study was undertaken to examine the value chain, value addition, marketing cost & margin, marketing efficiency and market integration of tilapia fish in selected areas of Bangladesh during the month of June-July 2013. The objectives of the study were to estimate costs and margins and to test market integration of tilapia fish. Primary and secondary data were used for this study. The higher marketing cost was incurred by paiker and the lowest by retailer. On the other hand, retailers earned the highest net marketing margins. Chain II was found the most efficient chain. Analysis of market integration shows that tilapia fish market in Bangladesh was well integrated. The findings of the study revealed that the marketing of tilapia was a profitable business and some recommendations were provided for the improvement of tilapia marketing in the country. Keywords: Value addition, marketing cost & margin, marketing efficiency and spatial co-integratio

Factors affecting structural properties and in vitro starch digestibility of extruded starchy foams containing bran

Article title: Factors affecting structural properties and in vitro starch digestibility of extruded starchy foams containing bran Article reference: YJCRS2207 Journal title: Journal of Cereal Science First author: Syed Ariful Alam Final version published online: 7-SEP-2016 Full bibliographic details: Journal of Cereal Science (2016), pp. 190-197 DOI information: 10.1016/j.jcs.2016.08.018Rye bran of two different particle sizes (coarse: 440 mm and fine: 28 mm) were prepared by milling of commercial rye bran. Coarse and fine rye bran was added into a blend of rye endosperm flour and corn starch (70:30) to achieve two bran levels, 15 or 30%, to produce directly puffed extrudates. A co-rotating twin screw extruder was used with a screw speed of 500 rpm, barrel temperature profile: 40-70-75-90- 95-110-110 C and constant feed rate of 67 g/min. Feed moisture content of 17% was used either as in barrel-water feed or as preconditioning. Fine bran addition effectively improved macrostructural properties as compared to coarse bran through increasing expansion by 3.3e11.7% and piece density by 3.8 e10.5%. Reduction of bran particle size significantly (P < 0.05) increased crispiness by 66.7e203.3%. Particle size reduction of bran had only minor influences on cell wall thickness, cell area and hydrolysis index of the extrudates. Extrudates made with 30% fine bran at in barrel-water feed provided the crispiest extrudates with lower in vitro hydrolysis index. The results demonstrated that the macrostructural and mechanical properties of extrudates containing rye bran can be improved by reducing bran particle size.Peer reviewe

Do rye product structure, product perceptions and oral processing modulate satiety?

Food structure and cephalic phase factors are hypothesized to contribute to postprandial satiety in addition to established food properties such as energy content, energy density, and macronutrient and fibre composition of a preload. This study aimed to evaluate if the structure of rye products has an impact on subjective feelings of satiety, and whether cephalic phase factors including oral processing, satiety expectations and perceived pleasantness modulate the interaction. Four wholegrain rye based samples (extruded flakes and puffs, bread and smoothie) were studied in terms of texture characteristics, in vivo oral processing, and expected satiety (n=26) and satiety as well as perceived pleasantness (n=16) (ClinicalTrials.gov number: NCT02554162). The vast textural differences between products were reflected in mastication process, perceived pleasantness and satiety expectations. Extruded products required the most intensive mastication. Rye puffs and rye bread which were characterized by a solid and porous structure, and showed better satiety effect in the early postprandial phase compared to other products. Mastication effort interacted with satiety response. However, the products requiring the highest mastication effort were not the most satiating ones. It seems that there are some food structure related mechanisms that influence both mastication process and postprandial satiety, the mastication process itself not being the mediating factor. Higher palatability seems to weaken postprandial satiety response.Peer reviewe

Process-induced structural properties and starch digestibility of high-fibre extruded products

This study focused on modification of rye bran to produce high fibre extruded cereal foods with a good texture and structure. Rye bran addition during extrusion is challenging due to high levels of insoluble dietary fibre, which leads to less expanded products and a hard texture. Bran modification by particle size reduction or fermentation significantly improved both the structural and textural properties of extrudates. Moreover, optimization of the processing parameters such as increasing the screw speed, lowering the water feed rate, as well as the use of in-barrel hydration regimens further improved the textural properties. The applicability of rye bran in extruded products could thus be improved by particle size reduction and fermentation. The extruded food structure and texture had a direct effect on the mastication and bolus formation process in the mouth. A hard and dense extrudate structure required more mastication effort than a crispy structure. Crispy and porous structures easily disintegrated in the mouth and produced smaller bolus particles than a hard and dense structure. A smaller particle size of the bolus was associated with increased starch hydrolysis. The bolus particle size was more effective than the matrix composition in altering the starch digestibility. Increased dietary fibre intake via appealing snack products could help reduce chronic diseases. Knowledge obtained in this thesis on cereal matrix formation and digestion and the effects of added dietary fibre on the structural and textural properties of extruded solid foams will help the food industry to develop healthy and appealing products. Understanding process-structure-digestibility relationships of high fibre extruded matrices is essential for designing health promoting foods

The effect of structure and texture on the breakdown pattern during mastication and impacts on in vitro starch digestibility of high fibre rye extrudates

The snack product category is lacking palatable, high dietary fiber containing products. This study explored how the addition of native or fermented rye bran influences the texture and sensory properties of endosperm rye flour based extrudates. In addition, mastication and bolus properties (n = 26), and in vitro starch digestibility were assessed. Three high fiber extrudates based on endosperm rye flour (EF) were produced with addition of either 40% native rye bran (NBE) or 40% fermented rye bran (FBE), and with no added bran (EFE) to achieve two pairs of extrudates to compare. EFE and FBE had different composition but resembled each other regarding macrostructure and the second pair (NBE vs. FBE) had similar core composition but different structure due to bran fermentation. The fermentation of bran was performed using exopolysaccharide (EPS)-producing strain Weissella confusa, which led to 3% (3 g per 100 g bran; dry weight) in situ dextran production. The compositionally similar extrudates (NBE vs. FBE) varied in both structure and instrumental texture: FBE were less dense, less hard and crispier than NBE. The extrudates with different composition (EFE vs. FBE) varied regarding instrumental texture: FBE were less hard and crispier than EFE. There were also subtle structural differences FBE being somewhat denser than EFE. NBE and FBE differed regarding sensory texture while textures of EFE and FBE were perceived similar. Mastication properties of the different products did not exhibit remarkable differences. There was a large number of smaller particles in both NBE and FBE bolus samples. The fragile structure of FBE, and its lower bolus viscosity, led to high in vitro starch digestibility. The results demonstrate that the structural attributes of the extrudates, rather than the core composition, dictate the breakdown pattern during mastication and in vitro starch digestibility. The extrudates with similar composition may be digested at different rates depending on their structural attributes. Although FBE had higher in vitro starch digestibility, its high DF content, palatable texture and improved sensory properties were important determinants underlying eating quality and therefore it could be a promising product to snack food category.Peer reviewe