Nutrient composition of extruded cowpea products

Three cultivars of cowpeas (Ife brown, Vita 5 and California black eye) were blended with either rice, corn or both rice and corn and banana puree. The blends were dry extruded on a low cost extruder. The average energy content was 440 Kcal/100 g, protein 20% and the trypsin inhibitor activity was reduced by 63–84%. The stachyose contents varied from 0.52 to 2.44%, raffinose 0.16 to 4.32% and sucrose 0.18 to 1.16 g% respectively. The colour of the products was acceptable and there was no evidence of browning in the products.     

Lycopene extraction from extruded products containing tomato skin

To determine the lycopene content of extruded products containing 10% tomato skin, the conditions for solvent extraction were optimised. After three extraction cycles at 50 °C each for 15 min at a solvent to meal ratio of 40:1, a maximum of 6.6 ppm lycopene was extracted. However, the extraction was considered incomplete, thus the product was digested by pancreatin prior to extraction. The extracted lycopene content was increased to 23.5 ppm using the optimum conditions of 20 min of digestion with 10 mg mL^?1 pancreatin. To validate the extraction efficiency at optimum conditions, a set of extruded products containing different lycopene concentrations was used. Digestion increased the extracted lycopene content by more than 2.5‐fold between the products. Furthermore, this inclusion significantly improved the correlation coefficient between the red colour and the extracted lycopene content. Therefore, including a digestion step prior to extraction by solvents was necessary to efficiently extract lycopene from extruded products.     

小米挤压膨化产品的吸湿动力学研究

挤压膨化食品极易从周围环境中吸收水分,导致脆性丧失;对吸湿动力学过程的了解有助于选定合适的包装材料和存储环境。将4种形态的小米挤压膨化产品在不同温度、相对湿度下吸湿,并对吸湿过程进行模拟分析。与扩散模型、Peleg模型相比,Weibull模型最能预测小米挤压膨化产品的吸湿行为。根据Weibull模型,同一温度下,初始吸湿速率随相对湿度增大而近似线性增大。同一相对湿度下,总体吸湿速率随温度升高呈近似线性增大。温度越低、相对湿度越高,平衡水分越高。不同样品间的平衡水分差异较小,而吸湿速度差异明显,尤其在低温—低相对湿度条件时。外层气孔结构的差异可能是样品间初始吸湿速率差异的主要原因。     

谷物组成对挤压膨化产品品质的影响

该实验以6种谷物(粳米、小麦、玉米、糯米、小米、燕麦)为原料,考察不同谷物原料组成成分与产品膨化特性之间的相关性。结果表明,挤压后谷物膨化制品的一些指标得到很大提高,如吸水性指数、水溶性指数;蛋白质含量及脂肪含量与膨胀度呈负相关,淀粉含量与膨胀度呈正相关,膨化制品中蛋白质及脂肪含量要控制在合理范围内;水溶性指数与蛋白质含量呈极显著正相关,与总淀粉含量呈极显著负相关;糊化度与总淀粉含量呈极显著正相关,与蛋白质、粗脂肪含量呈极显著负相关。粳米、小麦以及糯米的膨化特性要优于玉米、小米以及燕麦,其中糯米在膨胀度、体积密度、水溶性指数、糊化度、硬度以及脆度方面都表现较为优异,膨化性能最好。综上所述,6种谷物原料中,糯米、小麦和粳米的挤压特性较好,可作为挤压膨化的主要原料,玉米、小米以及燕麦可根据成本适量添加。     

挤压糖玻璃化桔油胶囊的性质分析

采用挤压方法将桔油包埋于玻璃态的碳水化合物基质中。主要考察了挤压条件下(挤压腔四段温度分别为65℃-85℃-105℃-95℃)螺杆转速为60r/min,不同DE值的麦芽糊精壁材、糊精和蔗糖壁材对糖玻璃化胶囊形成的性质影响,结合差示扫描量热法、傅里叶变换红外光谱、粒径分析仪及扫描电镜等对胶囊的微观结构进行了表征。结果表明,在挤压过程中桔油能很好的包埋,芯材主要以小液滴的形式分散于包埋的基质中,粒径大小绝大部分为2~5μm。形成的糖玻璃化胶囊没有新的化学键形成,是以物理分散的形式存在。     

几种食品添加剂对挤压即食食品丙烯酰胺形成的抑制效果研究

以马铃薯-小麦混合粉为原料,通过在挤压膨化即食食品中,添加不同种类、不同浓度的食品添加剂,研究不同添加剂对产品中丙烯酰胺含量的影响。结果表明:海藻糖、大豆多肽、茶多酚、竹叶提取物、氯化钙等食品添加剂的添加对挤压产品中丙烯酰胺含量的影响显著(p<0.05)。其中当氯化钙添加量达到0.5%时,产品中丙烯酰胺含量比对照减少了80%;大豆多肽添加量达到3%以上或竹叶提取物含量达到0.3%时,产物中丙烯酰胺含量对比对照组减少了50%。     

Properties of extruded whole grain cereals and pseudocereals flours

Common cereals such as wheat are widely used worldwide in extruded products. Nevertheless, other locally available grains would be beneficial for local consumers regarding taste preference, nutritional needs and sustainability. Locally available cereals, that is millet, teff, sorghum and pseudocereals, that is quinoa and amaranth flours were extruded at the same processing conditions, and the resulting properties were compared to those of extruded refined wheat flour. Amaranth flour contained the highest protein content (16%). Sorghum was the highest in calories because of its high lipid content (10%). The extrusion process greatly increased a water solubility index (WSI) of amaranth from 11% to 61%, while the WSI level of quinoa was almost not affected (WSI of 4%). The expansion properties varied differently among grain types. These grains had a sectional expansion index (SEI) ranging between 11 and 13, which could not achieve the performance of the refined wheat (SEI of 22). The lowest expansion was observed for amaranth flour which contained the lowest starch content. Sorghum extrudates, interestingly, provided comparable stress at rupture value to that of wheat. For the mechanical properties, none of these local grains could fully replace refined wheat at the employed extrusion conditions.     

Incorporation of whey products in extruded corn,potato or rice snacks

Sweet whey solids (SWS) or whey protein concentrate (WPC) were added at concentrations of 250 and 500 g/kg to corn meal, rice or potato flour to make snack products. Extrusion processing conditions included low shear, high shear, and the combination of high shear/low moisture. Increased specific mechanical energy (SME) was desired for expanding products, but SME was reduced as a result of incorporating WPC and SWS. Quality indices for expansion and breaking strength decreased significantly (P<0.05), indicating poor textural effects. By reducing the moisture and adding reverse screw elements, SME was increased, which increased product expansion and breaking strength.     

Impact of ripening stages of banana flour on the quality of extruded products

The study investigated the physical, nutritional and sensory properties of different ripening stages of banana during extrusion processing in combination with rice flour to develop quality snack products. Dehydrated banana flours at ripening stages 4, 5 and 6 (peel colour) were mixed separately at 40% banana to 60% rice flour levels. The mixtures were extruded through a twin-screw extruder at 120 °C barrel temperature, 220 and 260 r.p.m, screw speed and 12% feed moisture. Increase in ripeness indicated negative effect on expansion and water absorption capacity while increasing the water solubility index and moisture retention (wet basis) of the products. Protein and mineral (except for zinc and copper) content of the products were significantly different ( P  < 0.05) from 4 to 6 of the ripening stages. Most of the essential amino acids in the extruded products increased significantly ( P  < 0.05) at the ripening stage of 6. All the products were within the acceptable range in the 9-point Hedonic scale showing the best texture and flavour scores for stage 4 and 6, respectively. The extruded products show potential as snack products because of their nutritional quality and sensory acceptability.     

Effect of glutamate and inosinate on sensory and instrumental texture of extruded products

Expanded products have been developed by extrusion of non-conventional highly nutritious raw materials such as amaranth and chickpea blended with bovine lung. As sensory acceptance of these snacks is restricted, this study aimed at improving their texture, through the addition of monosodium glutamate (MSG) and disodium inosinate (IMP) flavor enhancers to the feeding material, or to the flavor added after the extrusion. Sensory and mechanical analyses showed that both enhancers affected texture, assessed by sensory and instrumental methods. Addition of IMP together with MSG to the chickpea-based snacks presented the best results. This beneficial effect was not observed in the amaranth-based snack, suggesting that IMP and MSG can favorably impact texture of extruded products depending on the amount and type of protein present.     

Thermal and rheological properties of breadfruit starch

The thermal and rheological properties of breadfruit starch were studied using DSC and 2 different rheometers. It was found that the gelatinization temperature of starch with excess moisture content (>70%) was at approximately 75 °C. A new endotherm was detected at about 173 °C when the moisture content was lower than required for full gelatinization of the starch. A detailed examination revealed that this endotherm represented the melting of amylose-lipid complexes. Breadfruit starch paste exhibited shear-thinning fluid characteristics, and good thermal and pH stability. The setback viscosity of the breadfruit starch was lower than that of potato and corn starches. The rheological properties of the breadfruit starch paste was well described by the Herschel-Bulkley model at a shear rate of 0 to 100 s(-1), where R(2) is greater than 0.95, and it behaved like a yield-pseudoplastic fluid. Both the storage modulus and loss modulus of the paste initially increased sharply, then dropped after reaching the gelatinization peak. Breadfruit starch gel showed both flexibility and viscosity. Suspension with 6% starch content exhibited very weak gel rigidity; however, this increased significantly at starch contents above 20%.     

Properties of whey protein isolates extruded under acidic and alkaline conditions

Whey proteins have wide acceptance and use in many products due to their beneficial nutritional properties. To further increase the amount of whey protein isolates (WPI) that may be added to products such as extruded snacks and meats, texturization of WPI is necessary. Texturization changes the folding of globular proteins to improve interaction with other ingredients and create new functional ingredients. In this study, WPI pastes (60% solids) were extruded in a twin-screw extruder at 100 degrees C with 4 pH-adjusted water streams: acidic (pH 2.0 +/- 0.2) and alkaline (pH 12.4 +/- 0.4) streams from 2 N HCl and 2 N NaOH, respectively, and acidic (pH 2.5 +/- 0.2) and alkaline (pH 11.5 +/- 0.4) electrolyzed water streams; these were compared with WPI extruded with deionized water. The effects of water acidity on WPI solubility at pH 7, color, microstructure, Rapid Visco Analyzer pasting properties, and physical structure were determined. Alkaline conditions increased insolubility caused yellowing and increased pasting properties significantly. Acidic conditions increased solubility and decreased WPI pasting properties. Subtle structural changes occurred under acidic conditions, but were more pronounced under alkaline conditions. Overall, alkaline conditions increased denaturation in the extruded WPI resulting in stringy texturized WPI products, which could be used in meat applications.     

Sensory acceptability of raw and extruded bovine rumen protein in processed meat products

The use of bovine rumen protein (raw and extruded) as a replacement for extruded soy protein concentrate in three meat products (pork sausage, chicken hamburger, and kibbe) was investigated. Similarity between rumen and soy protein meat products was assessed using triangle tests and sensory acceptability evaluated by consumer panelists using a nine-point hedonic scale. The addition of raw rumen protein was detected in all meat product types tested, while extruded rumen protein was only detected in kibbe. The addition of raw rumen protein decreased the acceptability of pork sausage aroma and flavor, but improved kibbe appearance, texture and overall acceptability. The addition of extruded rumen protein reduced the acceptability of chicken hamburger texture, but improved pork sausage flavor. Replacement of soy protein by bovine rumen protein is feasible based upon sensory results, but depended upon its form and the type of meat product to which it was added.     

Effect of guar gum content on some physical and nutritional properties of extruded products

The effect of guar gum (0-10%) added to flour (maize, potato, rice, and wheat) prior to extrusion on the microstructure, physical properties (texture, expansion, density, pasting) and nutritional properties (starch digestibility) was investigated. The inclusion of guar gum did not decrease starch digestibility; rather, at 10% guar gum rapidly digestible starch increased by 24%, 15%, 25% and 43%, in maize, potato, rice and wheat flour-based products, respectively. In general, increases in starch digestibility appear to be related to the weaker microstructure (i.e., lower textural hardness), larger matrix surface area, and lower viscosity (pasting properties) of extrudates containing guar gum. These results suggest that microstructural changes affect the starch digestibility of extrudates; nevertheless, probably other factors such as particle size during digestion may also play an important role.     

Evaluation of mannitol and xylitol on the quality of wheat flour and extruded flour products

Effects of polyols (mannitol and xylitol) on physical properties, pasting properties and dynamic rheological properties of wheat flour and the microstructure, water activity (A_w), radial expansion ratio (ER), oil absorption rate (OAR) and texture of extruded flour products were evaluated in this work. The results show that both mannitol and xylitol can promote gluten network formation, enhance tensile resistance and increase the storage modulus (G') and loss modulus (G'') of the dough. More dense and uniform particles were also found on the surface of extruded flour products in the presence of polyols by scanning electron microscopy (SEM). Furthermore, the A_w, hardness and chewiness were reduced while the ER and ORA were increased for extruded flour products by incorporation of polyols. Thus, the extruded flour products with improved quality by polyols exhibit great application prospect in food industry.     

Properties of extruded blends of wheat dried distiller grain flour with other flours

Zero, 10, 20 and 40% dried distiller grain (DDG) from wheat was blended with corn, potato, rice, and wheat flours at total moisture levels of 15 and 22% and extruded in a Brabender laboratory single screw extruder at three sets of barrel temperatures of 80, 130, 160°C; 100, 160, 210°C and 120, 190, 250°C at a constant screw speed (100 r.p.m.), screw configuration (3:1 compression ratio) and die size (3.175 mm). Resulting torque, yield, radial expansion (RA), longitudinal expansion index (LEI), density, water absorption index and colour were measured.
All the blends were successfully extruded over a wide temperature range. As the amount of DDG increased, in general torque, yield and RE decreased, and colour darkened while density and LEI increased. Wheat flour was the base material found to vary most from the above trends.     

Novel method for the determination of added annatto colour in extruded corn snack products.

There is considerable interest in determining the added levels of the natural dye annatto in foods like snack products, particularly because they are mostly consumed by young people. The objective was to use response surface methodology to develop a new method to analyse annatto in extruded snacks. A pretreatment of the samples was necessary, digesting the ground sample with alpha-amylase at room temperature. The pigment was extracted by shaking with ethyl acetate at room temperature, eight extractions being necessary for completion extract the pigment. Lipids were removed by alkaline saponification. Under these conditions, 100% of the bixin was converted into norbixin, which was then quantified by high-performance liquid chromatography. The method had a mean recovery of 97% and a coefficient of variation for duplicate analysis of 1%. Using this method, of the 13 commercial samples analysed, a parmesan cheese-flavoured snack product showed the highest level of dye expressed as norbixin (15.5 mg kg(-1)), whilst other brands of onion-flavoured snack products had the lowest levels (0.7 and 0.4 mg kg(-1), respectively).     

Rheological analysis of dough prepared with lentil flour at different moistures for production of extruded products

Extruded products like expanded puff product are prepared from lentil (Lens culinaris Medik) at different conditioning moisture (14, 18, 22 %) for constant temperatures, range from 100 to 210 °C, which was used during extrusion processing. The present study was aimed to investigate the effect of conditioning moisture at different temperature on the rheological behavior of lentil. It was determined that viscosity and yield stress of the lentil dough decreased with increase in conditioning moisture of flour used during extrusion process. Yield stress decreased by 68 and 80 % for conditioning moisture at 18 and 22 %, respectively as compared to those conditioning moisture at 14 %. This was attributed to the changes in the carbohydrates occur due to high extrusion temperature. Increasing the conditioning moisture during extrusion process decreased the fluid consistency index and increased the flow behavior index of the dough, demonstrating a lower viscosity and increased fluidity. All the samples revealed shear thinning behavior. The dough prepared using lentil shows depletion in gelatinization temperature with decreased in conditioning moisture as demonstrated by viscoelastic analysis (loss modulus, storage modulus, Tan δ) of the samples.