Comparison of the consistencies of cooked mashed potato prepared from seven varieties of potatoes

Potato protein concentrates (PPC) were isolated from potato juice of seven studied varieties by thermal coagulation of 6.0–6.2 pH juices at 90–95 °C, followed by freeze-drying. Three levels of PPC were added to cooked mashed potato to raise the protein contents to 3, 4 and 5%, along with three levels of dry potato to obtain similar dry matter contents in mashed potatoes after the additions. The consistency of cooked mashed potato was measured objectively by a “back extrusion cell” connected to an Instron 1140 texturometer. Studied varieties differed in their consistencies of cooked mashed potato which increased with the dry matter content and increased after applying additives: (PPC and dry cooked potato). In spite of the similar dry matter contents the hardness of cooked mashed potato was higher when the PPC was used as an additive than with the dry potato addition.     

Nutritional composition of UK retail potatoes,both raw and cooked

Over two seasons, four maincrop potato cultivars together with early varieties, were purchased from a range of retail outlets in three principal consumer areas (London, Birmingham and Glasgow). Samples were analysed for moisture, total nitrogen, non-protein nitrogen, fat, carbohydrates (sugars, starch and dietary fibre), vitamins and minerals. Analyses were carried out on both the raw and cooked (boiled, baked, roast and chipped) tubers every 12 weeks. Values for raw and cooked materials were compared with previously published figures, and cultivar, centre and seasonal effects were identified by analysis of variance. Nutrients found to be lower than the Food Composition Table data were riboflavin and niacin (50%), potassium (40%), iron, copper and zinc (20–30%); thiamin and total folate were 2–3 times higher, total ascorbate, initially similar, declined more rapidly after harvest. These differences were reflected in the values obtained for the cooked potato where the major difference was a reduction in the fat content of chips by about 40%. Cooking losses were similar to those in the Food Composition Tables. The main varietal effects were confined to the vitamins. Centre effects showed that potatoes from Glasgow had less ascorbate and dry matter but slightly more free sugars. The only significant seasonal effect was for total ascorbate where the second season was higher than the first.     

Physicochemical,textural and sensory properties of white soft cheese made from buffalo and cow milk mixtures

The physicochemical, textural and sensory properties of white soft cheeses made from three different buffalo and cow milk mixtures (100:0, 70:30 and 30:70) during 3‐month storage were studied. The increase in buffalo milk concentration resulted in increasing total cheese yield, dry matter (DM) and fat retention and fat in DM content. However, it caused reductions in moisture content, salt intake, hardness, chewiness, elasticity, sensory hardness and sensory cohesiveness of the samples. The percentage of water‐soluble nitrogen to total nitrogen increased during storage resulting in decreased fracturability, hardness (textural and sensory), cohesiveness (textural and sensory), springiness, chewiness and elasticity. The panellists evaluated the white soft cheese made with buffalo milk as the most acceptable.     

Microstructural,cooking and textural characteristics of potato (Solanum tuberosum L) tubers in relation to physicochemical and functional properties of their flours

Potato tubers from six different cultivars were freeze‐dried, ground into flour and analyzed for thermal, pasting and textural characteristics (using differential scanning calorimetry, Rapid Visco analyzer and Instron universal testing machine, respectively) to study the relationship between flour characteristics and cooked potato mealiness. The potatoes with higher sensory mealiness scores resulted in flours having lower transition and pasting temperatures, higher amylose content, setback, peak and final viscosity. The flour gels from the mealier potatoes also exhibited higher values of textural parameters such as hardness, cohesiveness, chewiness and springiness. The microstructure of the tuber parenchyma (studied using scanning electron microscopy), cooking and sensory characteristics of potatoes were found to be related to the pasting and textural characteristics of their flours. Potato cultivars with lower mealiness scores, loosely packed cell arrangement, with comparatively large‐size cells and thinner cell walls showed lower values of textural parameters for both raw and cooked potatoes. This information may prove useful for the selection of potato cultivars with desirable textural and flour‐making properties for specific end‐uses. Copyright © 2005 Society of Chemical Industry     

Cassava varietal screening for cooking quality: Relationship between dry matter,starch content,mealiness and certain microscopic observations of the raw and cooked tuber

Thirteen cassava (Manihot esculenta L Crantz) varieties from three successive annual harvests were screened for the mealiness of the cooked tuber, and the elasticity and smoothness of the pounded paste. Six were selected for further studies based on their mealiness and the starch and dry matter contents were determined. The diameter of the starch granules of the selected varieties and those of an irradiated M₁ V₂ population were measured. Microscopic examinations of the raw and cooked cells of the irradiated M₁ V₂ population were made. Correlations among all the parameters were studied. Varietal and seasonal differences in cooking quality were observed. There was no consistent relationship between mealiness of the boiled tuber and the elasticity and smoothness of the pounded paste. Varieties that were mealy were high in dry matter and starch content. The starch granules of mealy varieties were larger than those of nonmealy ones. There were no differences between mealy and non-mealy varieties in the arrangement of the cells or ‘cell condition’, of the raw tubers. However, the cells of the cooked tubers were held less cohesively, ie there was more ‘cell disorganisation’, in mealy varieties than in non-mealy ones.     

The effect of the pre-treatments and the long and short-term frozen storage on the quality of raspberry (cv. Heritage)

Results are presented of the effect of pre-treatments before freezing followed by long and short-term frozen storage (12 months at –18 °C and 24 days suffering temperature fluctuations between –18 °C and –12 °C) on quality parameters of raspberry. Pre-treatments were carried out with calcium, low methoxyl pectin, a combined solution, and results compared with untreated control fruits. Kramer shear, back extrusion, compression, and multiple penetration tests were used to measure rheological behavior. One-hundred mM CaCl₂ reduced the long and short-term frozen storage induced loss of firmness. For long-term storage at –18 °C, a softening of the tissue became evident between 3 and 12 months and at each date test the stored fruits were firmer than those without storage. For short-term storage with fluctuations, the loss of firmness was evident between 0 and 24 days, and at all the testing dates the stored fruits were softer than those without storage. Results evidenced a higher cell damage in the short-term frozen storage. Coefficients of softening per day suffering fluctuation were determined, the highest values being given by Kramer shear energy and back extrusion maximum force (>1%). Short-term frozen storage affected physical and physico-chemical characteristics, increasing the saturation (r) and the anthocyanins and decreasing the ascorbic acid of the raspberries. In both storage conditions, pre-treatments reduced the drip loss, which correlated best with the Kramer shear energy. Panelists detected mainly time effect on the sensory firmness. For long-term, sensory firmness and juiciness gave the highest correlations with back extrusion maximum force, while for the short-term, sensory firmness and drip loss gave the highest correlations with the Kramer shear energy. SEM revealed different degrees of mechanical damage to structure, which accounted for rheological behavior of the fruits.     

Chemical, Physical, and Sensory Properties of a Sweet Potato French-Fry Type Product During Frozen Storage

Chemical, physical, and sensory properties of a sweet potato Frenchfry type product were determined after 0, 3, 6, 9, and 12 months frozen storage. Analyses included measurements of dry matter, sugars, alcohol insoluble solids, carotene, vitamin C, color, texture and sensory panel scores for color, flavor and texture. Few changes were observed except for an appreciable loss (58%) in vitamin C and an apparent increase in carotene (27%). A partial drying treatment before freezing increased the rate of ascorbic acid loss. For the fried product, no appreciable storage-induced changes were noted in the sensory scores for color, flavor and texture thus indicating that the product had good stability in frozen storage.     

Characterization of Thermal Properties of Potato Dry Matter–Water and Starch–Water Systems

ABSTRACT: Potato dry matter samples of varying moisture contents were analyzed by differential scanning calorimetry (DSC). One endothermic and one exothermic transition were observed when the moisture content was < 50% (w/w) in the dry matter–water system. Both endothermic and exothermic transitions of potato dry matter were influenced by moisture content. One endothermic transition at about 66 °C was observed when the samples were reheated after 2 wk of storage at 5 °C. Gelatinization and retrogradation of starch are chiefly responsible for the endothermic transitions in the potato dry matter. The exothermic transition may originate from chemical reactions such as Maillard and caramelization during heating of a potato dry matter–water system when water is limited (< 50%, w/w) and at temperatures > 120 °C     

Functionality of Protein‐Fortified Extrudates

Fortification of extrusion feed formulations with proteins from selected sources will improve the health‐promoting quality of snack and breakfast foods. Molecular interactions among proteins, starch, lipids, water, and other constituents in the extrusion “melt” are the basis for extrudate appearance as well as textural, sensory, and physical properties. Covalent disulfide and sulfhydryl bonding as well as electrostatic, hydrogen, and hydrophobic affinity developing among molecules during extrusion determine extrudate sensory quality, digestibility, and nutrient availability. Extrudate quality is dependent on the physical profile of the feed material from particle size to moisture concentration, the mechanical profile of the twin‐screw extruder from screw speed to die aperture, and the temperature, pressure, and shear leading to specific mechanical energy delivered in the extruder. Methods to assess extrudate physical and sensory quality are presented. Protein concentration, feed moisture, and extrusion temperatures are most important to expansion, density, and texture of extrudates. Fortification with whey and wheat proteins results in acceptable extrusion of snack and breakfast foods. Extrusion generally improves protein quality and digestibility while retaining active nutrients.     

挤压变量对马铃薯方便粥品质特性的影响

以马铃薯全粉、大米粉为主要原料,采用双螺杆挤压微膨化工艺,联用常压连续气流膨化技术开发马铃薯方便粥.研究了马铃薯全粉含量、挤压温度、水分含量对马铃薯方便粥品质特性的影响,并采用因子分析法对马铃薯方便粥的品质特性指标进行综合评价.结果表明:随着马铃薯全粉含量、挤压温度的升高,马铃薯方便粥的颜色均逐渐加深,质构特性逐渐降低...     

不同品种马铃薯化学组成及香气成分的研究

研究通过测定武川县不同品种马铃薯:夏波蒂、费乌瑞它、康尼贝克、兴佳和冀张12的水分/干物质、碳水化合物(还原糖、淀粉)、维生素C、蛋白质、脂肪和膳食纤维的含量及香气成分,为马铃薯加工利用提供理论依据。结果表明:调查的5种马铃薯品种的水分76.94%~82.12%,干物质17.88%~23.06%,还原糖0.10%~0.23%,淀粉18.36%~20.33%,维生素C 12.39%~19.42%,蛋白质1.72%~2.56%,脂肪0.11(g/100 g)~0.22(g/100 g),膳食纤维0.27(g/100 g)~0.42(g/100 g);不同品种马铃薯香气成分存在明显差异,醇类、醛类、酸类、烃类和酮类化合物对香味形成有重要作用。     

Effects of corn particle size and source on performance of lactating cows fed direct-cut grass-legume forage

We conducted two experiments to evaluate the effects of corn supplementation, source of corn, and corn particle size on performance and nutrient utilization of lactating dairy cows. In experiment 1, treatments were 1) direct-cut grass-legume forage without supplement, 2) direct-cut forage plus 10 kg DM of ground dry shelled corn-based concentrate, and 3) direct-cut forage plus 10 kg DM of coarsely ground high moisture ear corn-based concentrate. In experiment 2, treatments were 1) direct-cut grass-legume forage plus 10 kg DM of ground dry shelled corn-based concentrate, 2) direct-cut forage plus 10 kg DM of coarsely ground high moisture ear corn-based concentrate, and 3) direct-cut forage plus 10 kg of DM finely ground high moisture ear corn-based concentrate. Both experiments were designed as 3 x 3 Latin squares replicated three times. In experiment 1, yields of milk and milk protein increased with concentrate supplementation, but were not affected by source of corn. Solids-corrected milk yield tended to increase with grain supplementation. Dry matter intake increased with concentrate supplementation, but was not affected by source of corn or corn particle size. Corn supplements decreased ruminal pH and acetate to propionate ratio and increased ruminal propionate concentration. Grain supplements reduced ruminal ammonia concentration, increased concentration of urine allantoin, and increased the urinary allantoin to creatinine ratio. In the second study, fine grinding of high moisture corn reduced fecal starch plus free glucose levels and tended to increase its apparent digestibility. In both experiments, starch plus free glucose intake was higher on the diets with dry corn, but its utilization was not affected by source of corn.     

Starch from Alberta potatoes: wet-isolation and some physicochemical properties

Starch content of six varieties of Alberta-grown potato tubers was more than 16% (wet basis). The tubers were wet fractionated in the laboratory and starch was recovered. The starch recovery ranged from 61 to 67%. The composition of the potato juice/fruit water (dry matter, protein, ash and mineral content) and starch isolations (moisture, starch, protein, lipid, ash, phosphorous and amylose content) was determined. The physicochemical characterization of the potato starch isolations were done in terms of granule size distribution, crystallinity (X-ray diffractometry), gelatinization (differential scanning calorimetry) properties, swelling factor and the changes in viscosity during heating and cooling of starch-water slurry (Brabender viscography). Substantial differences in the starch content of the tubers, fruit water composition and starch physicochemical properties were observed between potato varieties.     

FULL UNIAXIAL COMPRESSION CURVES FOR PREDICTING SENSORY TEXTURE QUALITY OF COOKED POTATOES

The prediction of six different sensory texture attributes of twenty-seven potato samples based on uniaxial compression curve features and full uniaxial compressions curves is reported. The data set comprised five varieties, sorted in dry matter bins, and sampled at two storage times. The predictions of most of the sensory texture attributes from full compression curves performed better than just using curve features. Furthermore, force-deformation curves are shown to give slightly better predictions than stress-strain curves. For most of the texture attributes better predictions were obtained using uniaxial compression data from raw potato samples as compared to cooked samples. This study is meant to open up a debate on interpreting the information in uniaxial compression curves in relation to sensory texture quality. Multivariate analysis can handle this and can further give insight about where in the curve the information relevant for the predictions of the sensory attributes is found.     

Replacement of fat with functional fibre in imitation cheese

The physical properties of imitation cheeses containing 21.3% dry matter (DM) resistant starch with moisture levels of 52–60%, as well as cheeses (60% moisture) containing 21.3–43.2% DM resistant starch were examined. Flowability of the heated cheese was assessed by an empirical method; the textural properties by texture profile analysis and dynamic rheology. Sensory analysis of cheeses was conducted by panellists using ranking tests. Increasing the moisture decreased cheese hardness did not affect flow but led to an undesirable ‘sticky’ and ‘clingy’ mouthfeel. Hardness increased linearly with increasing starch. Flow decreased at starch contents ⩾34.8% DM. Replacement of fat in the higher moisture cheeses resulted in the production of a good, firm cheese as assessed by a sensory panel. It was possible to incorporate up to 43.2% DM resistant starch into cheeses, a level higher than many ‘high fibre’ products, while maintaining acceptable functional properties.     

Relationship among the carotenoid content, dry matter content and sensory attributes of sweet potato

The sensory characteristics of biofortified sweet potato in Africa were explored over a wide range of carotenoid (0.4-72.5 μg/g fresh weight) and dry matter contents (26.8-39.4%). The logarithm of the total carotenoid content was correlated with the dry matter content (declining by 1.2% with each doubling of the carotenoid content) and a wide range of sensory characteristics that involve visual, odour, taste and textural characteristics. Multiple linear regression models were developed. The logarithmic relationship of colour to the carotenoid concentration means that those varieties with a relatively low carotenoid content may appear to be of similar intensity to those with a much higher and hence nutritionally beneficial carotenoid content.     

10个马铃薯品种在川中丘陵区冬作的品质综合评价与分类

为开展鲜食型和加工型马铃薯品种的综合评价与科学分类,本研究针对10个四川省川中丘陵区冬作马铃薯的主栽品种开展了外观指标(单薯重、薯块形状、表皮颜色、芽眼深浅和个数、果肉色差、果肉硬度)和营养指标(干物质率、淀粉含量、可溶性糖含量、可溶性蛋白含量、V_C和总酚含量)的测定分析与综合品质评价。应用SPSS软件对基础数据进行差异显著性和相关性分析表明,各品种间测定指标均呈现不同程度的差异,薯块果肉硬度和干物质率呈显著正相关(P<0.05);应用主成分分析对10项测定指标进行降维处理,评价得出10个品种的综合得分排名,其中川芋10号、川芋50和青薯9号综合排名前3;应用Ward聚类方法对供试品种的主要营养指标进行了系统聚类分析,将10个品种划分为4个类别,结合基础数据和主成分分析结果讨论了各类别马铃薯品种的品质特征。