Effects of sucrose and vegetable oil on properties of native cassava (Manihot esculenta Crantz) starch-based edible films

Biopolymer films and coatings from polysaccharides, proteins and lipids, formulated either with one or more components have the potential to control mass transfer and thus extend food shelf life. Due to the increase in the price of starches from traditional sources (such as corn), native or modified cassava starch has been recently considered as an economic alternative for the food industry. In this study, the effects of sucrose and vegetable oil as natural, cheaper and available plasticizer and moisture barrier material, on optical, mechanical and water barrier properties of cassava starch-based films were analyzed. Visual appearance and the polarized light microscopy data revealed that oil made the film opaque, and larger oil droplets were formed as sucrose content increased. The modification of the starch network, when sucrose was used at higher concentrations (15-20%), in combination with oil, weakened mechanical and water barrier properties. The behaviour of sucrose added to aqueous starch solution, in combination with oil, favored a development of larger droplets observed by polar microscopy, and which made the film matrix discontinuous and irregular. The heterogeneity of the film structure made the composite films fragile and facilitated water vapor diffusion. However, the film formulations containing low sucrose concentration (≤ 10 %) and an oil content of 10%, significantly reduced water vapor permeability, in comparison to film without oil. The formulations of composite film with low content of sucrose (≤ 10 %) showed smaller lipidic droplets and a structure more homogeneous by polar microscopy. Film thickness increased with total solid content in film matrix, and this effect was significantly pronounced as higher sucrose content (15-20%) was present with added vegetable oil. In addition to the linking with total solid content, this study revealed that, the thickness of films depends on reordering of molecular chains to form a more compact matrix in composite starch films, and this results in further increase film thickness. The composite films, thicker than the film control, were less cohesive due to less affinity between matrix components, and this resulted in anti-plastifiant behaviour of sucrose. Thus, sucrose used at higher levels, in combination with oil, induced negative effects on mechanical and water barrier properties of polysaccharide film. This study revealed the impact of the nature of molecular interactions on the structural characteristics and functional properties of composite matrix.Keywords: cassava, biofilm, starch, sucrose, lipi

Development of frozen-fried yam slices: Optimization of the processing conditions

The research performed on yam processing mainly concerns the production of crisps and flour. However, its transformation into deep-frozen French fries does not necessitate any other equipment than those used for potatoes. The industrial process of production of frozen French fries traditionally includes a pre-frying step. These steps contribute to the development of color and crispness, and the oil partially absorbed inhibits dehydration during the freezing step. The aim of this study was tooptimize frying conditions of deep-frozen fried yam (Dioscorea cayenensis var Kponan) slices. The effect of pre-frying time and temperature, final frying time and temperature on the oil uptake, texture, dry matter and colour of the fried yam slices has been studied. Frying conditions optimized with Box-Behnken experimental design were short pre-frying and frying conditions at high temperature characterized by prefryingtemperature at 157-170°C during 5-9s and frying temperature at 181-188°C for 2min 15s-2min 30s; or long pre-frying and frying conditions at low temperature characterized by pre-frying temperature at 150-158°C during 10-15s and frying temperature 170-177°C for 3-3min 15s. An adiabatic system was also developed by means of an insulator in which the core temperature of fried yam slices can be maintained constant at about 55°C after 15min of cooling, facilitating texture measurements at constant temperature. The present results may help in choosing the yam slices frying condition to be applied in order to achieve the desirable fried yamslices quality, required for protection against certain diseases like obesity. These models may also provide guidance as to how to control these quality parameters by altering four key environmental factors, pre-frying temperature and time and, final frying temperature and time. This process can also be commercialized and does not necessitate any other cost for equipment than those used for potatoes French fries and might be an interesting way of added value processing for this highly perishable yamtuber

Effects of cattle and poultry manures on organic matter content and adsorption complex of a sandy soil under cassava cultivation (Manihot esculenta, Crantz)

This study examined the A and B horizons of deep, developed and moderately unsaturated sandy ferrallitic soils amended with cattle and poultry manures under cassava (Manihot esculenta Crantz) cultivation. Therefore, a plot experiment was carried out by using a randomized complete blocks design in 4 replications and fields treatments which included unfertilized (control) and one dose (10 t/ha) of both manures. The study of the different fractions of animal manures showed that the poultry had the greatest content of C (organic carbon), N (nitrogen), P (phosphorus), K (potassium), Ca (calcium) and C:N ratio (p < 0.01). However, the value of Mg (magnesium) in the studied manures was not significantly different (p < 0.01). The manure treatment significantly increased the soil organic matter contents from 0.46 to 2.8 and 1.1% respectively with poultry and cattle manures (p < 0.01). Organic fertilizer significantly increased the cation exchange capacity from 1.7 to 12.75 and 3.8 me:100 g and the bases saturation content from 47 to 80 and to 76% respectively with the poultry and cattle manures (p < 0.01). The organic fertilizer showed significant effect on earthworms populations Hyperiodrilus africanus (Oligochaeta, Eudrilidae) in the soil, with 128 and 85% respectively about the poultry and cattle manures compared to the control (p < 0.01).Key words: Cattle manure, poultry manure, cassava, organic matter, cation exchange capacity, basessaturation content

Effect of glycerol, peanut oil and soybean lecithin contents on the properties of biodegradable film of improved cassava starches from Côte d’Ivoire

— Edible films have been successfully used in the food packaging industry for several decades. Today natural polysaccharides, including cassava starch,are increasingly being used in the production of such biodegradable edible films and food packaging. In Côte d'Ivoire, there are improved cassava varieties whose starches have not yet been tested in the production of biodegradable films. In thisstudy, the optical and mechanical properties and the water solubility of starch-based composite films of four improved cassava varieties withadded glycerol, peanut oil and soy lecithin were determined. Starchwas obtained by cold water extraction from native cassava from the varieties Bocou 1, Bocou 2, Yavo and TMS. Films preparation was made bycasting methodwithcassava, glycerol (25-30 %), peanutoil (5-10 %) and soybean lecithin (0-5 %). Increasing the glycerol content, increased L*color valueand elongationat break and decreased a*, b*, colourdifference (ΔE*ab) and tensilestrength of the composite films. Also, increasing the oil content from 5 to 10%, increased the opacity, b*, ΔE*ab, water solubility, elongationat break but decreased L*, a* and tensilestrength. Similarly, increasing the soy lecithin content from 0 to 5%, increased the opacity, L*, b* and ΔE*ab, but decreased a*, of the starch-based composite films. The results suggest an ideal formulation of 4% starch/25% glycerol/5% oil/5% soy lecithinfor a film with optimum mechanical properties with low solubility

CARACTERISATION SENSORIELLE, CHIMIQUE ET INSTRUMENTALE DE L’IGNAME BOUILLIE (DIOSCOREA SPP.)

Quatre variétés d’igname des espèces Dioscorea alata et D. cayenensis-rotundata couramment trouvées sur les marchés urbains de la Côte d’Ivoire ont été cuites sous forme bouillie et testées pour leurs caractéristiques sensorielles et physicochimiques. Les attributs de texture, friable et farineux, et le goût sucré sont les descripteurs les plus déterminants de ce mets. Du point de vue biochimique, les variétés se sont distinguées selon que leur maturité soit précoce ou tardive. L’analyse factorielle multiple (AFM), apermis d’observer une synergie entre la matière sèche et les attributs friable et farineux. Aucune relation n’a été observée entre ces caractères et la dureté mesurée avec le pénétromètre. Le goût sucré est indicateur d’une texture farineuse mais, révélateur d’un faible taux de sucres réducteurs. Boiled yam was cooked with four varieties of yam varieties usually found on the urban markets of Ivory Coast and tested for their sensory and physicochemical characteristics. Crumbliness, mealiness, and sweetness are the most important descriptors of this dish. At biochemical level, the varieties were distinguished according to their early or late maturity.The multiple factorial analysis has revealed a synergy between the dry matter content and crumbliness and mealiness. No relation was observed between these attributes and hardness measured with the penetrometer. Sweetness is highly related to mealiness but is an indicator of low reducing sugar conten

Development Of Frozen-Fried Yam Slices: Optimization Of The Processing Conditions

The research performed on yam processing mainly concerns the production of crisps and flour. However, its transformation into deep-frozen French fries does not necessitate any other equipment than those used for potatoes. The industrial process of production of frozen French fries traditionally includes a pre-frying step. These steps contribute to the development of color and crispness, and the oil partially absorbed inhibits dehydration during the freezing step. The aim of this study was to optimize frying conditions of deep-frozen fried yam ( Dioscorea cayenensis var Kponan) slices. The effect of pre-frying time and temperature, final frying time and temperature on the oil uptake, texture, dry matter and colour of the fried yam slices has been studied. Frying conditions optimized with Box-Behnken experimental design were short pre-frying and frying conditions at high temperature characterized by pre-frying temperature at 157-170°C during 5-9s and frying temperature at 181-188°C for 2min 15s-2min 30s; or long pre-frying and frying conditions at low temperature characterized by pre-frying temperature at 150-158°C during 10-15s and frying temperature 170-177°C for 3-3min 15s. An adiabatic system was also developed by means of an insulator in which the core temperature of fried yam slices can be maintained constant at about 55°C after 15min of cooling, facilitating texture measurements at constant temperature. The present results may help in choosing the yam slices frying condition to be applied in order to achieve the desirable fried yam slices quality, required for protection against certain diseases like obesity. These models may also provide guidance as to how to control these quality parameters by altering four key environmental factors, pre-frying temperature and time and, final frying temperature and time. This process can also be commercialized and does not necessitate any other cost for equipment than those used for potatoes French fries and might be an interesting way of added value processing for this highly perishable yam tuber

Water Vapor Permeability and mechanical properties of edible films on native starch from improved cassava variety in Côte d’Ivoire

A study in Côte d'Ivoire entitled "artisanal and industrial valorization of native cassava (Manihot esculenta Crantz) and yam (Dioscorea sp)" starches showed that the film produced with starch cassava and vegetable oil showed the most promising coatings capabilities. This film was designed without plasticizer and showed mechanical limits. So, the presence of plasticizer could overcome the fragility of the film, with a commonly used slurry of 15-40/g of glycerol in 100 g of starch. The properties of starch films can be further improved by producing composite films with incorporation of functional additives. Thus, in this present study, starch-based films have been strengthened with addition of a plasticizer (glycerol), an emulsifier (soy lecithin) and a preservative (potassium sorbate). Films were prepared with 5 % oil, 25 and 30 % glycerol, 0 and 5 % soy lecithin and 0.2 g potassium sorbate. Mechanical (Tensile strength and Elongation at break) and water vapor properties of native cassava starch improved variety Olekanga films were determined. Increasing glycerol concentration and soy lecithin addition had no significant effect on water vapor permeability of all films. In opposite significant difference (p <0.05) of glycerol concentration was observed on tensile strength and elongation at break of films. Which was not the case when soy lecithin concentration is increased from 0 to 5 %. Tensile strength decreased with increase in glycerol concentration. Opposite behavior was observed for elongation at break. Films on native starch from improved cassava variety Olekanga in Côte d’Ivoire were less resistant, very elongable with acceptable water vapor permeability

Fumure organique et productivité du manioc (Manihot esculenta Crantz) en Côte d\'Ivoire

La litière de volaille et la fumure de bovin ont été apportées sur des sols ferrallitiques sableux, moyennement désaturés à Toumodi, Centre de la Côte d\'Ivoire, en vue de l\'intensification de la culture du manioc (Manihot esculenta Crantz). A 15 mois après plantation, les fumures ont entrainé une augmentation des rendements moyens de 4 variétés de manioc, qui ont été de 40 t.ha-1 pour le témoin et de 63 t.ha-1 et 61 t.ha-1 respectivement, pour la litière de volaille et la fumure de bovin. A 18 mois après plantation, les rendements ont chuté de 42 t.ha-1 sous le témoin à 21 t.ha-1 sous fumure de volaille et 41 t.ha-1 sous fumure de bovin. A cette période, les taux moyens de tubercules avariés ont atteint 55 % et 44 %, respectivement sous litière de volaille et fumure de bovin contre 30 % pour le témoin. A 15 mois, les teneurs en matière sèche ont été significativement différentes suivant les traitements (37,6, 37,4 et 37,3 % avec la litière de volaille, la fumure de bovin et le témoin). La fumure de volaille a influencé l\'apparition des symptômes du Virus Africain de la Mosaïque du Manioc (note de 1,75 avec la fumure de volaille contre 1,25 pour le témoin). Pour la plupart des variables mesurées, l\'effet variété a été significatif. La fumure organique a favorisé une meilleure intensification de la culture du manioc jusqu\'à 15 mois après plantation.Chicken litter and cow manure were applied on a moderately unsaturated sandy ferrallitic soil in Toumodi (Centre of Côte d\'Ivoire) in order to acheive intensification of cassava (Manihot esculenta Crantz)cropping. At 15 months after planting, fertilizer application significantly improved cassava yields in 4 varieties, with values ranging from 40 t.ha-1 under no fertilization to 63 t.ha-1 and 61 t.ha-1, when chicken and cow manures were used, respectively. At 18 months after planting, root yields dropped from 42 t.ha-1 under the control to 21 t.ha-1 and 41 t.ha-1, with chicken and cow manures, respectively. During the same period, the number of rotten tubers reached 55 and 44 %, under chicken and cow manures, respectively, as compared to 30 % for the control. At 15 months after planting, dry matter rates were significantly different among the treatments (37.6, 37.4 and 37.3 % with chicken and cow manures and the control, respectively). The chicken manure favoured the symptoms of the african cassava mosaic virus (score 1.75 with chicken manure, as compared to 1.25 for the control). For most variables, there was a significant varietal effect. Organic fertilizer was found to be useful toward the intensification of cassava cropping, more so for shorter vegetative cycle (15 months) than longer ones (18 months). Keywords: Fumure, manioc, rendement, Côte d\'Ivoire.Agronomie Africaine Vol. 19 (3) 2007: pp. 271-27