Starch structure and some properties of cocoyam (Xanthosoma sagittifolium and Colocasia esculenta) starch and raphides

Studies were conducted on the structure and rheological properties of three cocoyam varieties [Xanthosoma sagittifolium (red-flesh), Xanthosonia sagittifolium (white-flesh) and colocasia esculenta] starches and raphides in an attempt to characterize them. The microstructures of starch granules and raphide sizes, which were obtained from the distal, middle and apical sections of the raw cocoyam samples, were examined using a light microscope. Evaluations of the rheological properties of the cocoyam species were also conducted, using a Brabender viscoamylograph. No distinct variation was observed in starch granule sizes of the two Xanthosoma species. Starch granules sizes in the ranges of 0.74–1.19 and 0.74–1.10 μm were obtained for the Xanthosoma species (red-flesh) and Xanthosoma species (white-flesh), respectively. Significantly smaller sizes (0.05–0.08 μm) of starch granules were observed for Colocasia esculenta. Microstructures of raphide sizes which were obtained from the distal section of the cocoyam species showed significant differences (P⩽0.05) among the varieties, with the Colocasia species having more pronounced needle-like structures. Evaluation of the rheological properties of the cocoyam flours, using the Brabender viscoamylograph, showed considerable variations among the varieties, especially between the Xanthosoma species and the Colocasia species. The C. esculenta showed lower hot paste viscosity but higher thermal stability than the Xanthosoma species. Peak viscosity was highest in the X. sagittifolium (red-flesh) variety while the white-flesh variety showed the least tendency to retrogradation.     

Development and Quality Evaluation of a Non-Alcoholic Beverage from Cocoyam (Xanthosoma sagittifolium and Colocasia esculenta)

Cocoyam tubers were processed into non-alcoholic beverage, flavoured with 0.5% and 1.0% extracts of ginger and alligator pepper respectively. Two varieties of cocoyam, namely Colocasia esculenta and Xanthosoma sagittifolium were used. The purpose of this study is to develop an acceptable flavoured non alcoholic beverage from cocoyam and thereby increase the utilization of this under-utilized crop. The proximate, vitamins C and A, mineral content, microbial and sensory evaluation were conducted on the products to assess the highest preference. Values for pH ranged from 3.00 to 3.86 and the total titratable acidity (TTA) from 0.50 – 0.82 with ginger flavoured samples rated higher than that of alligator pepper. Total solids varied significantly and ranged from 5.00 – 6.02% with alligator pepper samples being higher than ginger. Vitamin C content ranged from 1.02 – 1.98 × 10⁻⁴ mg/100 g while vitamin A content ranged from 6.04 to 14.41 μg/100 g with ginger flavoured samples having higher vitamin C and A than the alligator flavoured ones. The minerals evaluated showed a decreasing trends with increase in the concentration of each spice. The sensory results showed that significant differences (p < 0.05) existed between the different flavoured samples and not between varieties. The microbial analysis showed that the cocoyam non-alcoholic beverage is safe for human consumption. Generally, the beverage had good consumer preference with the 0.5% ginger flavoured being the most preferred.     

Effect of taro (Colocasia esculenta) flour addition on the functional and alveographic properties of wheat flour and dough

BACKGROUND: Taro is a plant widely produced in tropical areas for its underground corms. Taro corms are highly perishable owing to their high moisture content. In order to limit post‐harvest losses and improve the production and consumption, production and utilization of taro flour have been envisaged. In connection with this, the incorporation of taro flour into wheat‐based products has been reported to increase their keeping quality. Before consideration is given to taro flour as a substitute for wheat in bread manufacture, it is necessary to characterize the functionality of the composite flour and dough. The present study investigated the physicochemical and alveographic properties of wheat–taro composite flour. RESULTS: Three varieties of taro flour (WCN, RIN and KWN) were incorporated into wheat flour in proportions of 10%, 20% and 30% (w/w) and the water absorption capacity (WAC), retrogradation index (RI), foam capacity (FC) and other functional properties were measured. In addition, characteristics of dough rupture pressure (P), extensibility (L), elasticity index (Ie) and strength (W) of flour made from the different composites were measured using an alveograph. The results showed that WAC significantly increased from 132% (wheat flour) to 156% (30% composite flour), while RI significantly decreased from 38% to a mean value of 22%. Principal component analysis revealed that WAC and P formed a group of variables negatively correlated with a second group made of RI, FC, W, Ie and L. CONCLUSION: Incorporating taro flour up to a level of 10% had no significant effect on the functional and alveographic properties of the flours. This suggested that in order to guarantee the quality of bread made from wheat–taro composite the level of taro addition should not exceed 10%. Copyright © 2007 Society of Chemical Industry     

Functional properties of raw and precooked taro (Colocasia esculenta) flours

Functional properties such as bulk density, water and oil absorption, foam capacity and stability, and viscosity of five raw and precooked taro ( Colocasia esculenta ) flours were studied. Proximate analyses of the taro flours indicated they were low in fat, protein and ash, but rich in starch and total dietary fibre. Heat processing affected the functional properties of taro flour. the raw taro flours were slightly different from each other for the tests on bulk density, water retention, and viscosity. On the other hand, the cooked flours showed no significant differences for the tests on oil retention, gelation and foaming.     

Exploring the functionality of starches from corms and cormels of Xanthosoma sagittifolium

Xanthosoma sagittifolium, belonging to the araceas family, represents an attractive alternative as a starch source. Nevertheless, as a rhizome plant two differentiated parts could be distinguished named corms and cormels." by "However, the rhizome of Xanthosoma sagittifolium has two differentiate parts named corms and cormels of Xanthosoma. Granules morphology, composition, hydration properties, pasting/thermal behaviour, as well as gelling performance were assessed. Scanning Electron Microscopy (SEM) revealed different morphology, granules were organised as aggregates in starch isolated from corms. Corms starch displayed lower hydration properties, lower apparent viscosity during heating and cooling and higher gelatinisation temperatures than cormels starch. Gels from corms starch showed less syneresis than cormels starch, but no significant differences were observed regarding their hardness. Therefore, the part of the araceas plant from which the starch is extracted must be always defined, because significant differences in their functionality are ascribed to their morphological origin.     

Comparative studies of some properties of undehulled, mechanically dehulled and manually dehulled cowpea (Vigna unguiculata Walp. L.) flours

A comparative evaluation was made of some physico‐chemical and rheological characteristics of undehulled, manually dehulled and mechanically dehulled cowpea (Vigna unguiculata Walp. L.) flours from brown and white varieties of the legume. The flours were used to prepare steamed bean paste, ‘Moinmoin’, which was analysed for some sensory parameters. Dehulling and dehulling methods had no appreciable influence on the physical characteristics and proximate composition of the flours, except ash content, which was slightly higher in undehulled flour samples. Amylograph pasting characteristics of the flours showed varying trends because of dehulling method and/or presence of seed coats. ‘Moinmoin’ samples prepared from the flours received similar ratings for all sensory attributes, with no significant differences (P < 0.01 and P < 0.05), except for the low‐rated (poorer) colour of the undehulled brown product.     

Dehulling characteristics,sensory and functional properties of flours from selected cowpea varieties

BACKGROUND: The knowledge of dehulling characteristics is very important in the selection of cowpeas for flour production. In this study the sensory and functional properties of cowpea flour as influenced by dehulling method (wet and dry/mechanical dehulling) and cowpea variety (white, maroon and mottled) were investigated. RESULTS: White cowpea showed a significantly different (P < 0.05) and higher dehulling rate (DR > 97%) for all dehulling methods. Maroon and mottled cowpeas were poorly dehulled (DR < 10%) when using the wet method (WD). Dry dehulling (DD) was effective on all three varieties (DR > 94%). The highest yield of flour was observed with white cowpea (80% for DD and 96% for WD). The beany odour intensity of flours was dependent on the method of dehulling used. Flour functionality was more significantly influenced by cowpea variety than by dehulling method. CONCLUSION: Dry dehulling could be recommended for cowpea flour production, as this method was found to be more effective on the selected cowpea varieties. Owing to the observed variation in flour functionality among cowpea varieties, the choice of a particular variety for flour production will depend on the intended use of the flour. Copyright © 2009 Society of Chemical Industry     

Effect of drying temperatures on starch-related functional and thermal properties of acorn flours

The application of starchy flours from different origins in food systems depends greatly on information about the chemical and functional properties of such food materials. Acorns are important forestry resources in the central and southern regions of Portugal. To preserve these fruits and to optimize their use, techniques like drying are needed. The effects of different drying temperatures on starch-related functional properties of acorn flours obtained from dried fruits of Quercus rotundifolia (QR) and Quercus suber (QS) were evaluated. Flours were characterized for amylose and resistant starch (RS) contents, swelling ability, and gelatinization properties. Drying temperature mainly affected amylose content and viscoamylographic properties. Amylograms of flours from fruits dried at 60 °C displayed higher consistency (2102 B.U. and 1560 B.U., respectively, for QR and QS). The transition temperatures and enthalpy were less affected by drying temperature, suggesting few modifications in starch structure during drying. QR flours presented different functional properties to those obtained from QS acorn flours. The effect of drying temperatures were more evident in QR.     

Physicochemical and functional properties of full fat and defatted cashew kernel flours

Full fat and defatted cashew kernel flours were prepared and analysed for their physicochemical and functional properties. There were significant increase in protein and carbohydrate contents of the flour as a result of defatting. The defatted flour possessed higher Ca, P, Na and K contents. It had improved gel strength, foaming and emulsion properties. Foam capacity for the full fat and defatted flours increased from 42% to 50% and 55% to 57% with increased NaCl concentration up to 0.25 and 0.05  m , respectively. The foam capacity and stability of the flours were also pH dependent. The emulsion activity and stability of both flours decreased with increasing NaCl concentration. Minimum and maximum protein solubility were at pH 4 and 8, respectively for the full fat and defatted flours. These results suggest that defatted cashew flour may have potential application as a functional ingredient and as a supplement in foods.     

Taioba (Xanthosoma sagittifolium) Leaves: Nutrient Composition and Physiological Effects on Healthy Rats

Several studies have shown that fruits and vegetables contribute to protect against degenerative pathologies such as cardiovascular diseases, diabetes, and cancer, mainly due to the presence of dietary fiber (DF) and polyphenols. Taioba (Xanthosoma sagittifolium) is an edible aroid widely grown in many parts of Africa, America, and Asia. The tubers portions of taioba are widely consumed; however, the leafy portions are generally discarded, despite their high nutritive value. In this study, we have partly characterized the DF of lyophiized taioba leaf (LTL), and assessed the possible protective effects on biochemical parameters and on bile acid (BA) production in colon and cecum, when fed to healthy rats for 4 wk. Forty‐five Wistar rats were assigned to either of 5 groups: group 1 received AIN 93G diet (CG: Control); group 2 received AIN 93G containing 2.5% of cellulose + 2.5% inulin (CEIN_5%); group 3 received AIN 93G containing 2.5% of cellulose + 2.5% taioba fiber (CETA_5%); group 4 received AIN 93G containing 5% cellulose + 2.5% taioba fiber (CETA_7.5%); group 5 received AIN 93G containing 5% cellulose + 2.5% of inulin (CEIN_7.5%). LTL showed high contents of total fiber, predominantly comprising insoluble DF with glucose as the major monomer. Rats receiving LTL had increased fecal mass and fat excretion, and improved BA profiles by diminishing the proportion of secondary acids, thus suggesting that consumption of taioba leaf may have the property of lowering the risk of colon cancer.     

Isolation and partial characterization of Mexican taro (Colocasia esculenta L.) starch

Taro starch was isolated from Mexican variety and its morphological, physicochemical, and molecular characteristics were evaluated. Yield starch (in dry basis) was 81%, and this starch had low AM content (2.5%). Taro starch granules showed a mixture of shapes with sizes between 1 and 5 µm. Taro starch presented an A‐type XRD pattern with a crystallinity level of 38.26%. Solubility and water retention capacity did not change in the temperature range of 50–70°C and thereafter they increased as temperature increased too. Taro starch showed high peak viscosity due to its high AP content. The peak temperature of gelatinization of taro starch was 80.6°C with an enthalpy value of 10.6 J/g, with low retrogradation rate due to its low AM content. Weight‐average molar mass (Mw) and gyration radius (Rz) of taro starch were 1.21 ± 0.8 × 10⁹ g/mol and 424 ± 70 nm, respectively. Taro tuber could be an alternative for starch isolation with functional and physicochemical characteristics for food and non‐food applications.     

Physicochemical and functional properties of ten cultivars of seem (Lablab purpureus L.), an underexploited bean in Bangladesh

BACKGROUND: Increasing global protein consumption has led to the demand for new sources of food protein, particularly plant sources. Many inexpensive but protein‐rich bean cultivars have not been well evaluated and are thus underutilised. In this study the physicochemical and functional properties of seeds of ten seem cultivars were assessed. RESULTS: In agreement with their sizes, seeds of Airet had the highest 1000‐seed weight and volume, while those of Bari had the lowest. In terms of proximate composition (g kg^?1), protein content ranged from 240.08 (Ashina) to 292.63 (Puti), fat content from 31.47 (Goalgadda) to 38.40 (Puti), ash content from 32.80 (Puli) to 45.53 (Goalgadda) and fibre content from 21.90 (Tatulia) to 28.90 (Noldog). Hydration (g kg^?1) and swelling (mL L^?1) capacities ranged from 1688.60 and 1850.43 (Goalgadda) to 1999.40 and 2208.66 (Rupbhan) respectively. Similarly, cooking time (min) varied from 114 (Rupbhan) to 179 (Goalgadda). Lowest gelation concentration was in the range 80–100 g kg^?1. Water and fat absorption capacities (g kg^?1) ranged from 941.00 and 644.44 (Ashina) to 1043.33 and 749.26 (Puti) respectively. Foaming capacity and stability (mL L^?1) ranged from 443 (Puli) to 635 (Puti) and from 314 (Ashina) to 643 (Rupbhan) respectively. CONCLUSION: Seeds of seem cultivars appear to be a promising food in terms of their protein content and functionality. Copyright © 2009 Society of Chemical Industry     

Composition and nutritive value of cormels of Colocasia esculenta (L.) Schott

The nutritional quality of the cormels of Colocasia esculenta (L.) Schott cultivar ‘Guavir’ was determined chemically and biologically in feeding experiments with weanling rats. The contents of starch and unavailable carbohydrates (cellulose, hemicellulose and pectin) were 54 and 15% of the dry matter respectively. Lipid accounted for less than 1% of the dry matter. Palmitic, oleic and linoleic acids were the main fatty acids in the lipids, with linoleic acid predominating. The content and fatty acid composition of the individual lipids was examined. Crude protein amounted to 10.4% of the dry matter. This protein was low in the sulphurcontaining amino acids and tryptophan, but contained adequate levels of the other essential amino acids. Diets containing raw cormel meal gave severely depressed net protein utilisation (NPU) and total nitrogen and carbohydrate digestibility when fed ad libitum to weanling rats. Both NPU and nitrogen and carbohydrate digestibility improved when the cormel meal was cooked prior to inclusion in the diets but such diets still did not support growth in weanling rats.     

Comparative evaluation of instant 'poundo' cocoyam (Colocasia esculenta) and yam (Dioscorea rotundata) flours produced by flash and cabinet drying

Cocoyam, an important staple crop especially among the low-income earners in tropical regions of the world, is highly underutilised for industrial applications. This study investigates the nutritional, colour and rheological properties of instant flours (‘poundo’) from two cultivars of Colocasia esculenta (white-NCe010 and purple-NCe003) and Dioscorea rotundata (var. Oginni), and sensory attributes of doughs prepared from reconstituted flours. Tubers were processed into instant flours using cabinet and flash drying methods. Significant differences (P < 0.05) in the proximate and mineral composition and pasting properties of flours were found. Sensory panellists rated reconstituted poundo yam (8.17–8.20) and white cocoyam (7.50–7.95) higher than purple cocoyam (6.60–7.10) meals. Influence of drying method on sensory characteristics of flours was not significant. Instant poundo cocoyam and yam flours could serve as novel convenience and ready-to-eat food products which could contribute to increasing the commercial and industrial application options for these underutilised tubers beyond their present basic use.     

Effect of debranching and heat‐moisture treatment on the properties of Thai rice flours

High and low amylose Thai rice flours (KC and ML, respectively) were used in this work, to increase the resistant starch (RS) content in the flour. Pullulanase debranching followed by heat‐moisture treatment (DHMT) altered the pasting properties, which increased the shear stability to the flours. The gelatinisation temperature determined by DSC was increased and the more retrogradation occurred in treated flour compared to the native flour. The SEM observation showed that the treatment did not change the morphology of the granules in both flours. The slowly digestible starch (SDS) content in DHMT KC was higher than in the native KC. The RS content in the treated ML flour was increased to 18.31% from 11.59% in native flour. These concluded that the treatment affected the digestibility, while maintaining the granular structure.     

Physicochemical and rheological characteristics of commercial nixtamalised Mexican maize flours for tortillas

Three commercial nixtamalised Mexican maize flours (CNMFs) designated HI‐A, HI‐B and HI‐C were evaluated in this work. For each brand, four samples corresponding to four consecutive months of production were evaluated. Tortillas prepared by the traditional process of nixtamalisation were used as the control. The maize flours and their respective tortillas showed variations between samples in their physical, chemical and rheological parameters. The three commercial maize flours incorporated additives and preservatives. The moisture content, colour, pH, subjective water absorption capacity, water solubility index, water absorption index and swelling capacity of flours showed strong differences between the three CNMFs with respect to the chemical analysis. Important differences in the protein, calcium and amylose contents were observed. Tortillas from CNMFs had a blander maize flavour, less desirable texture and staled more rapidly than traditional tortillas. Some modifications are required in the current Official Mexican Quality Standard, principally in the appropriate selection of additives and levels used in the preparation of CNMFs. © 2000 Society of Chemical Industry     

Rheology and microstructure of achu,a food based on taro (Colocasia esculenta L. Schott), as affected by method of preparation

The functional properties of flour and the organoleptic, rheological and microscopic characteristics of traditionally made achu were compared with those of reconstituted achu prepared from the taro variety Ibo coco. Organoleptic analyses showed that reconstituted achu was generally softer in consistency and less appreciated than traditional achu. In general with respect to functional properties, the estimated water absorption capacity, bulk density, blue value index and penetrometric index were lower for traditional achu than for reconstituted achu. In contrast, the viscosity of traditional achu was significantly higher than that of reconstituted achu. Light microscopic observations revealed that reconstituted taro achu is a smooth starch gel containing broken parenchyma cells whereas in traditional achu, the paste is mainly composed of whole cells within a starch gel. Coulter particle size analyses of achu showed a peak at median 122 µm for traditional achu whereas reconstituted‐flour achu had its median at 143 µm. All the functional, rheological and microscopic analyses reflect the higher degree of starch gelatinisation in the reconstituted achu. From this study, it is suggested that boiling the whole corms before drying could improve the texture of the reconstituted achu. Copyright © 2006 Society of Chemical Industry     

Isolation and physicochemical characterisation of starch from cocoyam (Colocasia esculenta) grown in Malawi

BACKGROUND: The aim of this study was to determine the physicochemical properties of starches isolated from Malawian cocoyams and compare them with those of cassava and corn starches. RESULTS: The purity of the isolated starches varied from 851 to 947 g kg^?1 and pH from 4.93 to 6.95. Moisture, ash, protein, fat and amylose contents ranged from 104 to 132, 0.3 to 1.5, 3.5 to 8.4, 0.9 to 1.6, and 111 to 237 g kg^?1, respectively. Cocoyam starches gave higher potassium and phosphorus but lower calcium levels than the other starches. The shape of starch granules varied from spherical to polygonal with cocoyam starches displaying smaller‐sized granules than cassava and corn starches. Cocoyam starches gave a higher wavelength of maximum iodine absorption and blue value but lower reducing capacity values than cassava and corn starches. The extent of acid hydrolysis of the starches also differed. Cocoyam starches exhibited amylopectin molecules of higher molecular weights but amylose molecules of lower molecular weights than cassava and corn starches. Cocoyam starches exhibited lower water absorption capacity and swelling power, paste clarity and viscosity but higher solubility, gelatinisation temperatures and retrogradation tendencies than cassava and corn starches. CONCLUSIONS: The physicochemical properties of native Malawian cocoyam starches vary among the different accessions and differ from those of cassava and corn starches. Copyright © 2010 Society of Chemical Industry     

Production and characterization of oxidized cassava starch (Manihot esculenta Crantz) biodegradable films

Plastic is one of the most common pollutants in the environment. Therefore, the number of studies on the use of biodegradable packaging is increasing. Starch is the primary material used in the production of biodegradable plastics due to its natural abundance and high biodegradability. Yet, the strong hydrophilic character of starch presents a challenge. Therefore, the modification of its structure through oxidation may yield interesting results as the viscosity reduction. The objectives of this work were to obtain cassava (Manihot esculenta Crantz) starch oxidized with 0.8 and 2.0% active chlorine, to develop biodegradable films and characterize their mechanical properties, solubility in water, permeability to water vapor, degree of swelling, and sorption isotherms. Biodegradable films were produced with starch concentrations of 2, 3, 4, and 5% w/w and 25% glycerol (g/100 g starch) added as a plasticizer. Images of the films were obtained with an atomic force microscope and allow to observe a smooth surface and the absence of starch granules in the film produced with oxidized starches. The tensile strength of the biodegradable film produced with oxidized starch (0.8% active chlorine) was 80 MPa. The value of permeability to water vapor was 1.613 × 10⁻⁹ kg/day/m/Pa, and the average solubility was 41%. The sorption isotherms showed that biodegradable films made with oxidized starches cannot be used in environments with relative humidity below 35% or above 90%.     

Nutrient and functional properties of composite flours processed from pregelatinised barley,sprouted faba bean and carrot flours

Mixture response surface methodology was used to study the effects of blending ratio (barley, faba bean and carrot) and faba bean sprout durations (1, 2 and 3 days) to improve nutrients and functional properties of bassoo (a traditional food in Ethiopia). Addition of sprouted and roasted faba bean and dried carrot flours significantly (P < 0.05) increased iron, zinc, total carotenoid (TC), water solubility index (WSI), water hydration capacity (WHC) and a_w. Models generated were fitting with high coefficient of determination R²: 0.74, 0.94, 0.99, 0.99, 0.94, 0.94, 0.94, 0.96 and 0.99 for iron, zinc, TC, condensed tannin, ferric reducing power, a_w, WAI, WSI and WHC, respectively. The study showed blending of pregelatinised barley, sprouted and roasted faba bean and dried carrots flours from 50% to 65%, 25% to 35% and 10% to 15%, respectively, led to achieve desired functional and nutritional quality studied.