Changes in the carbohydrate constituents of yam tuber (dioscorea rotundata,poir) during growth

The amounts of sugars, starch, hemicellulose and cellulose in yam tubers were estimated at different stages of maturity and in yam tuber (“EgbodO”) sections. Maltose, sucrose, glucose and fructose were the free sugars identified in the ethanolic extracts of the yam samples. Sucrose formed the bulk of the total sugars. The “bottom” portion of the “Egbodo” yam tuber was richer in total sugars (4.9%) than either the “middle” (1.8%) or the “head” (2.4%) regions. Starch accounted, respectively, for 60, 77 and 78% of total carbohydrates in the “bottom”, “middle” and “head” regions of the “egbodo” yam tuber. A peak value of 84% starch was obtained 6 months after planting the yam setts. Its decrease to 64% at 8 months has been partly attributed to reduced photosynthetic activity through yellowing and subsequent loss of leaves. The sum of cellulose and hemicellulose, regarded as non-available carbohydrates was less than 7% of the total carbohydrates. The linear fraction, amylose, formed about 17.8% of the starch prepared from whole yam tubers of varying maturities, and from yam tuber sections, the remaining being amylopectin. The observed amylose and amylopectin values did not vary significantly over the period of observation. These amylose and amylopectin fractions had iodine affinities of 17 and 0.1%, respectively.     

Mealiness and sogginess in sweet potato

Sweet potato (var. Jersey) and yam (var. Velvet) are ‘mealy’ and ‘soggy’ varieties, respectively, of Ipomoea batatas Poir. In the raw state the storage roots of both have virtually the same histological structure: more or less abundant starch grains in the parenchyma cells and few intercellular spaces. After baking, the sweet potato shows rounded cells which are full of gelatinised starch and are separated by numerous small, capillary-like intercellular spaces. The baked yam has very little starch, shrivelled cells, ruptured and shrunken cell walls and many large intercellular cavities. The relationships of histological structure to textural properties in these roots and in the mealy and soggy varieties of the tuber of the Irish potato are discussed.     

RELATIONSHIPS OF SELECTED WHEAT PARAMETERS TO BURGHUL-MAKING QUALITY

Ten Triticum aestivum and eleven Triticum turgidum var. durum varieties were screened for their one thousand kernel weight (1000 KW), particle size index (PSI), sodium-dodecyl-sulfate (SDS) sedimentation volume, flour swelling power, protein content, amylose content and swelling power of starch. The varieties were processed to Burghul (parboiled wheat) and utilized in the preparation of Burghul Mufalfal and Kibbeh. The products were rated sensorially for particle separation and hardness (Burghul Mufalfal) and denseness (Kibbeh). Marked differences were noted between the aestivums and durums as to their 1000 KW, PSI and SDS-sedimentation volumes. Significant correlations were observed between the sensory ratings of the two Burghul-based products and the 1000 KW, PSI and SDS-sedimentation volumes. Cluster analysis, using the chemical/physicochemical parameters as variables, identified two clusters; a “durum” cluster (11 durums, 2 aestivums) and an “aestivum” cluster (8 aestivums). The varieties of the “durum” cluster yielded quality Burghul Mufalfal and Kibbeh; the varieties of the “aestivum” cluster yielded inferior Burghul Mufalfal and less compact Kibbeh. Quality Burghul is best-processed from large size and hard-grained varieties of low SDS-sedimentation volumes (mostly durums) having 1000 KW > 34.5 g, 31.9 < PSI < 45.6 and 13.8 mL < SDS-sedimentation volumes < 30.1 mL.     

Effects of Wheat Starch Contents on Malt Qualities

The relationships between wheat starch content and wheat malt qualities were studied in the present work. Six wheat varieties that were typical in starch, protein content and amylopectin/amylose ratio were selected from 12 wheat varieties and germinated under the same conditions. The decreased degree of total starch content after malting had a positive correlation (r = 0.8020, P < 0.1) with the amylopectin/amylose ratio of the raw wheat. Extracts of wheat malts were influenced by starch content and the amylopectin/amylose ratio of the raw wheat. When the amylopectin/amylose ratio was in the range 3.65:1?3.93:1, extracts of the malts had significant positive correlation (r = 0.967, P = 0.002) with the starch content of the raw wheat. In this investigation a suitable amylopectin/amylose ratio (3.65:1 to 3.93:1), a high starch content and a low protein content were the characteristics of a wheat variety suitable for malting.     

HPLC Determination of Sugars in Raw and Baked Sweet Potatoes

Isocratic HPLC techniques were developed for the quantitative analysis of sugars in raw and baked sweet potato roots. The major sugars in raw roots: sucrose, glucose, and fructose, were quantitated with a cation exchange resin column (Aminex HPX-87C) heated to 75°C using HPLC-grade H₂O as the mobile phase and refractive index detection. The major sugars in baked roots (convection oven or microwaved) were maltose, sucrose, glucose, and fructose. They were quantitated with an aminopropyl bonded phase column (Bio-Sil Amino 5S) at 21°C using a 70% CH₃CN:30% H₂O mobile phase and refractive index detection. Over 95% recoveries of all sugars added to sweet potato roots were obtained.     

Rapid Estimation of Potato Tuber Quality by Near‐Infrared Spectroscopy

Starch and protein parameters of potato tubers were estimated by near‐infrared (NIR) spectroscopy measurements of the crude potato mash. Calibration was carried out with a condensed data set of original 1481 individual samples from a varying number of varieties and breeding lines, grown at eight locations over a three‐years period. Validation of the models was performed with an independent data set (n = 133). Starch content of potato tubers was determined with the official under‐water weighting procedure of the EU, and could be predicted with 90% confidence. The NIR model of phosphorus content of starch had a prediction confidence of 53%. Total protein content could be predicted, too (62% confidence), whereas the amount of coagulable protein was not predictable (R² = 0.25). Despite the different qualification levels of the models, guiding to concrete prediction tools or to a very rough estimation graduating from “low” to “high”, the NIR technique enables potato starch processing plants to optimise both potato starch quality and processing efficiency.     

Effect of home preparation practices on the content of provitamin A carotenoids in coloured sweet potato varieties (Ipomoea batatas Lam.) from Kenya

The content of β-carotene was determined in raw peeled, boiled peeled and roasted peeled roots of six orange- and yellow-fleshed sweet potato varieties from Kenya to evaluate their vitamin A potential before and after household preparation. The boiling and roasting procedures were similar to traditional methods used in Kenya. Dried products, chips and flour, of the variety Zapallo were also analysed. The varieties differed in dry matter and β-carotene content (1240–10,800 μg/100 g fresh weight (FW)) and thus in vitamin A content (100–830 RE/100 g FW). As sweet potato roots are consumed after heating, the loss of all-trans-β-carotene during preparation should be taken into account. Boiling of roots of the selected varieties seemed to result in a higher true retention (TR) of all-trans-β-carotene than roasting and TR of all-trans-β-carotene seemed to be dependent on the variety (42–128%). Preparation of chips by drying resulted in a significant reduction of the all-trans-β-carotene content of approximately 21%, which was further reduced when flour was produced from chips. The varieties Tainung and SPK-004 can be recommended for consumption especially after boiling in order to enhance the vitamin A intake in Kenya. Both varieties have a high content of vitamin A, the losses after boiling are rather low and both varieties have high consumer acceptability.Industrial relevanceThe content and stability of β-carotene in sweet potato is an issue that is particularly important for developing countries with high prevalence of vitamin A deficiency. In order to prolong the shelf life of sweet potato, it is necessary to implement and develop industrial or small scale processing methods so that it is possible to produce sweet potato products with highest possible vitamin A values in these countries. In developed countries, focus is on innovation of new products with a good taste and a high health value. Consequently, sweet potato and sweet potato products might have a future as healthy foods in developed countries, and therefore there is a need to build up an industry that can provide the people in these countries with high quality sweet potato foods.     

1-甲基环丙烯对甘薯块根贮藏过程中品质相关指标的影响

以目前广泛栽培的4 个鲜食型甘薯品种为材料,研究了1-甲基环丙烯（1-methylcyclopropene,1-MCP）对贮藏过程中甘薯块根品质相关指标的影响。结果表明,1.00 μL/L的1-MCP对甘薯块根中可溶性糖、直链淀粉、支链淀粉以及胡萝卜素含量等甘薯品质相关指标有显著影响,并且这种影响因甘薯品种不同而存在明显差异。与对照处理相比,1-MCP处理的4 个甘薯品种可溶性糖含量达到高峰值的时间均有所提前,1-MCP显著提高了‘广87’和‘烟薯25’块根中可溶性糖含量峰值。1-MCP显著降低了0～7 d贮藏期间‘广87’、‘烟薯25’和‘龙薯9号’块根中直链淀粉含量,显著提高‘广87’和‘苏薯16’贮藏期间直链淀粉含量峰值,显著降低了‘苏薯16’和‘烟薯25’在贮藏28～120 d期间块根中直链淀粉含量。1-MCP还显著降低了‘苏薯16’和‘龙薯9号’在贮藏28～120 d期间的支链淀粉含量。1-MCP也显著改变了胡萝卜素含量的变化趋势,提前了‘广87’、‘苏薯16’和‘龙薯9号’在贮藏期间胡萝卜素含量达到最低值的时间。     

不同品种马铃薯淀粉功能性质的相关性及主成分分析

分析黑龙江、甘肃、北京3个地区的11个马铃薯品种制备得到淀粉的水分含量、色泽、直链淀粉含量、透光率、碘蓝值、溶解度、膨胀度、胶稠度、质构特性。结果显示,不同品种各指标差异显著,直链淀粉质量分数的变化范围是10.96%～16.64%;相关性分析发现不同品种的各品质指标间存在显著的相关性,直链淀粉与淀粉提取率(r=0.468 3)、膨胀度(r=0.520 9)、硬度(r=-0.472 1)、咀嚼性(r=-0.449 6)分别呈显著的相关性。主成分分析结果显示,前4个主成分的特征根大于1,可以解释原有数据的信息,综合主成分得分,陇薯9号的综合值排名第一,荷兰薯的综合值最低。     

Amylose and amylopectin molecular fractions and chain length distribution of amylopectin in 12 varieties of Ghanaian sweet potato (Ipomoea batatas) flours

Sweet potato (Ipomoea batatas) is a commonly cultivated root crop in tropical and subtropical regions, including Ghana. Different varieties of sweet potato have been bred, in order to expand its utilisation within the food and industrial sector. This study analysed flours made from 12 recently developed Ghanaian sweet potato varieties in terms of their amylose and amylopectin molecular fractions and amylopectin chain length distribution. Starch content of the sweet potato flours ranged from 49 to 77 g/100 g dry matter, with 11 of the varieties containing above 60 g/100 g dry matter. An orange-fleshed variety, Apomuden, had the lowest amount of starch (48.9 g/100 g dry matter), while the cream-fleshed variety Histarch had the highest (77.3 g/100 g dry matter). The flours from the 12 sweet potato varieties had intermediate amounts of amylose, within the range 10–30 g/100 g dry matter, and showed typical molecular distribution according to size-exclusion chromatography (SEC). The fine structures of amylopectin, as revealed by anion-exchange chromatography, contained features common for starches of C-type X-ray pattern, but some structural differences were also observed.     

Digestibility of Sweet Potato Raw Starches by Glucoamylase

Three crude glucoamylase preparations from Rhizopus sp., Chalara paradoxa and Aspergillus sp. K-27 were used to determine the digestibility of raw starches from eight sweet potato varieties. Granule sizes and amylose contents were also measured. The average granule sizes ranged between 10.5 and 14.2 μm. The amylose contents varied between 18.2 and 21.8%. The hydrolysis rates for the raw starches by any of the three glucoamylases were similar. However, starch of the variety Hi-starch had a slightly lower hydrolysis rate than other starches when Rhizopus sp, enzyme was used.     

Mechanical and Microstructural Properties of “Wet” Alginate and Composite Films Containing Various Carbohydrates

Composite “wet” alginate films were manufactured from alginate–carbohydrate solutions containing 5% alginate and 0.25% pectin, carrageenan (kappa or iota), potato starch (modified or unmodified), gellan gum, or cellulose (extracted or commercial). The “wet” alginate films were used as a model to understand co‐extruded alginate sausage casings that are currently being used by several sausage manufacturers. The mechanical, optical, and microstructural properties of the calcium cross‐linked composite films were explored. In addition, the water holding capacity and textural profile analysis properties of the alginate–carbohydrate gels were studied. The results indicate that the mechanical properties of “wet” alginate films/casings can be modified by adding various carbohydrates to them. Alginate films with pectin, carrageenan, and modified potato starch had significantly (P < 0.05) greater elongation values than pure alginate films. The alginate–pectin films also had greater (P < 0.05) tensile strengths than the pure alginate films. Alginate films with extracted cellulose, commercial cellulose, and modified potato starch had lower (P < 0.05) puncture force, distance, and work values than the alginate control films. Transmission electron microscopy images showed a very uniform alginate network in the control films. Several large cellulose fibers were visible in the films with extracted cellulose, while the cellulose fibers in the films with commercial cellulose were difficult to distinguish. Despite these apparent differences in cellulose fiber length, the 2 cellulose films had similar puncture and tensile properties.     

Studies on Starch from an Indian Crocus

The molecular properties and granular appearance of a starch from an Indian crocus (Crocus sativus) have been examined by methods involving iodine-staining, enzymic degradation, gel chromatography and scanning electron microscopy. The granules were relatively small (3 – 15 μm), and had a rough surface and flattened facets indicative of close packing. The amylose content of 27.4% was rather higher than that of many cereal and potato starches but came within the higher end of the range of “normal” values.     

Physicochemical Characteristics of 18 Cultivars of Nigerian Cowpeas (V. uniguiculafa) and Their Cooking Properties

Eighteen cultivars of cowpeas (V. unguiculata) were analyzed for cooking time, swelling capacity, leached solid, percent seed coat, seed density, amylose, tannins, proteins, and soluble sugars. The physicochemical characteristics varied with the seed coat color, the hilum color, and the skin texture. The cooking time was positively correlated to protein, seed density, percent seed coat, swelling capacity and leached solids, and negatively correlated to the levels of amylose, soluble sugars and tannins. There were significant correlations (p < 0.05) between sugars and swelling capacity, protein and seed density; and seed density and swelling capacity. The mean percent seed coat was significantly different (p < 0.05) between the varieties with wrinkled seed coats and those with smooth seed coats.     

Determination of Amylose by Differential Scanning Calorimetry

A differential scanning calorimetry (DSC) method for the determination of amylose as its amylose-L-α-lysophosphatidylcholine (LPC) complex is described. Potato amylose/amylopectin mixtures covering the range of 0–95% amylose were heated in the presence of LPC, cooled and then reheated to follow melting of the amylose-LPC complexes formed during the cooling phase. A linear relationship (r = 0.98) was obtained between the amylose content of the mixtures and the enthalpies of the amylose-lipid complexes. This linear calibration was used to predict the amylose content of various native starches, rice flours, wheat flour, durum wheat semolina, and lyophilized raw potato on the basis of the melting enthalpy of their amylose-LPC complexes. Except for the potato samples, amylose contents determined by the DSC method were in good agreement with those obtained from a colorimetric assay.     

The potential contribution of bread buns fortified with beta-carotene-rich sweet potato in Central Mozambique

BACKGROUND: Orange-fleshed sweet potato is an efficacious source of vitamin A. Substituting wheat flour with orange-fleshed sweet potato in processed products could reduce foreign exchange outlays, create new markets for producers, and result in increased vitamin A consumption among consumers provided there is adequate retention of beta-carotene during processing. OBJECTIVE: To explore whether substituting 38% of wheat flour (by weight) in bread buns ("golden bread") with boiled and mashed orange-fleshed sweet potato from fresh roots or rehydrated chips would produce economically viable beta-carotene-rich products acceptable to Mozambican rural consumers. METHODS: Modified local recipes maximized sweet potato content within the limits of consumer acceptability. Sensitivity analysis determined parameters underlying economic viability. Two samples each of buns from five varieties of orange-fleshed sweet potato were analyzed for beta-carotene content. Processed products with at least 15 microg/g product of trans-beta-carotene were considered good sources of vitamin A. RESULTS: Golden bread made from fresh roots of medium-intensity orange-fleshed sweet potato varieties met the good source criterion, but bread from lighter-intensity sweet potato varieties did not. Bread from rehydrated dried chips was not economically viable. Consumers strongly preferred golden bread over pure wheat flour bread because of its heavier texture and attractive appearance. The ratio of the price of wheat flour to that of raw sweet potato root varied from 3.1 to 3.5 among the bakers, whose increase in profit margins ranged from 54% to 92%. CONCLUSIONS: Golden bread is a good source of beta-carotene and is economically viable when the price ratio of wheat flour to raw orange-fleshed sweet potato root is at least 1.5. Widespread adoption during sweet potato harvesting periods is feasible; year-round availability requires storage.     

Genotypic Variations in Quality and Shelf-Life of Fresh Roots of Philippine Sweet Potato Grown in Two Planting Seasons

Sweet potato breeding in the Philippines has recently integrated root quality and shelf-life attributes in varietal development. In this study, the harvest and post-harvest quality of the fleshy roots of different sweet potato genotypes were determined. These genotypes included the existing recommended varieties and the elite selections from the polycross breeding nursery and were grown during the dry and wet planting seasons. Dry matter, starch, sugar and protein contents of freshly harvested roots were found to differ widely with genotype. During storage at ambient temperatures, starch content decreased, sugar content increased and in some genotypes dry matter increased. Protein content of the stored roots varied only slightly from that of fresh roots. The different genotypes also differed in the degree of weight loss, shrivelling, decay and consequently, shelf-life. Some genotypes had short-lived roots (less than 1 month) while others had roots which were still marketable at the end of the 3-month storage period. Root quality and shelf-life similarly varied with planting season. Some genotypes had increased dry matter, starch and sugar contents and long shelf-life when planted in the dry season while others had these characteristics when produced in the wet months. Protein content generally decreased in wet-season-produced roots. However, a number of genotypes had comparable root quality and shelf-life regardless of planting season.     

Changes in the carbohydrate constituents of cassava root-tuber (Manihot utilissima pohl) during growth

Sucrose formed the bulk of the sugars in cassava root-tubers, accounting for more than 69% of the total sugars. Other sugars included fructose, glucose and maltose. Maltose was consistently present as the lowest amount. The highest concentration of sugars (5.7%) was attained nine months after planting. Starch accounted for the highest proportion of the carbohydrates. A peak value of 81% was observed eight months after planting. The decrease to 78% at nine months was accompanied by an increase in sugar concentration from 3.5% to 5.7%. The sum of cellulose and hemicellulose constituted the non-available carbohydrate fraction to non-ruminants. This was less than 7% of total carbohydrates. Paper chromatography of the neutralised hydrolysate of the extracted hemicellulose revealed the presence of glucose and xylose only. The amylose content of cassava starch varied between 16.2% and 17.4% during growth. This variation was significant at 1% F level. The separated amylose had an iodine affinity of 17.0% while amylopectin had 0.1%.     

Effect of innovative pre-treatments on the mitigation of acrylamide formation in potato chips

The aim of this research was to evaluate the reduction of acrylamide (AA) formation in potato chips applying innovative pre-treatments. Raw potato slices were subjected for 5 and 15 min to: dipping in water; dipping in Aureobasidium pullulans L1 yeast water suspension; dipping in water or in yeast water suspension after pulsed electric fields (PEF) in order to investigate a possible synergistic effect of pre-treatments. The raw potato samples were analysed for AA precursors and, after frying, for AA by using HPLC-MS/MS. In addition, the final potato chips main quality parameters were evaluated.Compared to untreated potato chips, yeast treatment promoted a reduction of AA formation mainly at the longest dipping time (15 min). PEF treatment followed by water dipping was the most effective in reducing AA for both the studied treatment times. The combination of PEF and yeast treatments led only a slight reduction of AA formation.Industrial relevanceThe Commission Regulation (EU) 2017/2158 has established new acrylamide (AA) benchmark levels in different foods due to its negative classification as “probably carcinogenic to human”. For this reason, food industries are interested in developing different processing methods to reduce the AA formation and at the same time to maintain an acceptable quality of final products. Fried potatoes (French fries and chips) are the most vulnerable foods in terms of high content of AA formation, being rich in the main Maillard reaction substrates, such as asparagine and reducing sugars, and characterized by a high surface to volume ratio. Among the strategies recently suggested for the reduction of AA in potato chips, pulsed electric fields (PEF) and yeast pre-treatments are very promising, having the potentiality to reduce AA precursors in raw potato tissues. In this study the possibility to apply yeast and PEF pre-treatments on raw potato slices with suitable processing times for a possible industrial application were evaluated.     

Seasonal Effects on the Physico-chemical Properties of Starch from Four Cultivars of Cassava

Four varieties of cassava plants were cultivated at CIAT in Colombia and harvested on four different occasions with a view to evaluating whether there was any relationship between the texture of the cooked roots and the constituent starch. The organoleptic qualities of the cooked roots showed considerable differences in ‘glassiness’ and hardness of texture, both between varieties and times of harvest. The starch granules were isolated and examined by a variety of techniques. The size of the granules did vary with the seasons but there were only minor differences in the x-ray crystallinity, the elution patterns of iso-amylase-debranched material (including the amylose content), the proximate composition of the starch and the time course of digestion by glucoamylase. None of these provided a basis for explaining the differences in cooked texture.