Relationship Between Extrusion Conditions and System Parameters of Extrusion Cooking of Cassava and Soybean Blends: Application of Response Surface Analysis

Blends of cassava flour and partially defatted soybean four were processed in a single-screw extruder. Experimental design with feed moisture (FM)(16, 20, 24 gwater/100g flour), amount of soybean (10–30 gsoybean/100g flour) and barrel temperature (120, 145, 170 oC) as independent variables produced 17 different combinations that were studied using Box-Behnken Design of response surface methodology to investigate the effect of these variables on extruder system parameters, namely, product temperature (PT), residence time (RT), machine throughput (MT) and specific mechanical energy (SME). The recorded values for all responses varied from 121 to 175 oC, 42.34 to 65.11 seconds, 3.65 to 4.56 and 159.01 to 213.63kJ/kg, respectively.  Second-order polynomials were used to model the extruder responses as a function of process variables. All three variables affected responses significantly especially their linear terms (P<0.05) and all the fitted models were all significant (P<0.05) and correlated with experimental data (R2 ³ 0.934). Keywords: Cassava flour, Soybean flour, Product temperature, Residence time, Machine throughput, Specific mechanical energy

DESIGN AND CONSTRUCTION OF A TUNEL DRYER FOR FOOD CROPS DRYING

Conventional sun drying of tropical crops often result in low quality product due to unpredictable nature of weather. Utilizing mechanical dryer such as tunnel dryer can improve the quality of the products as well as increasing the acceptability of such crop in global market. In this study, a tunnel dryer in two modes of operation (co-current and counter-current) with a capacity of 35kg of chips per batch was designed, fabricated and tested. The dryer had a chamber volume of 0.408m3; the number of trucks in the tunnel was 6, each truck contained 6 trays. The operating temperature of the pilot dryer ranged from 50 to 150 oC and air velocity ranged from 2 to 8 m/s, respectively.  Cassava chips was used to test the dryer and the results showed that the dryer reduced the moisture content from 75  to 14% in 8 hours with drying constant of 2.42/h. &nbsp

Production and Storage of Cassava Chips for Reconversion into Gari

Cassava chips (7% moisture level) produced from cassava root (IITA 94/0561) was stored for 6 months in high density polyethylene bag. Stored chips were coarse milled, rehydrated to 62.51% and seeded with fresh cassava mash (FCM) at levels of 5%, 10% and 20%. The resulting mash was fermented for 72 hr, with pH monitored every 24 hr, and processed to gari. Yield and swelling capacity of gari were determined. Sensory evaluation was carried out on water soaked gari and gari paste (‘eba’). While least values for pH was obtained in FCM throughout the fermentation period, there was reduction in values in all samples with increase in fermentation time from 30.01 to 33.40%. Yield of gari from the seeded chips ranged from 64.4-72.3%, while that of FCM was 18.7%. Swelling capacity of gari ranged from 2.0 - 3.0 in FCM and that seeded with 20% FCM, respectively. Sensory evaluation result revealed that gari produced from cassava chips seeded at 10% level is adequate for making ‘eba’ while that seeded at 5% level is adequate for consumption as soaked gari (p<0.05). Use of stored cassava chips with 10% FCM for gari production could be encouraged to reduce postharvest problem of cassava roots and the drudgery of gari processing. Keywords: Cassava chips, cassava mash, gari, ‘eba’, postharvest losses, storag

Crustal thickness across the southern Appalachians

M.S.Leland T. Lon

Technological aspects of preparing affordable fermented complementary foods.

The requirements and manufacturing procedure of complementary (weaning) foods is discussed. Nutritional requirements for infants (aged 6-12 months) include approx. 3 MJ energy and 14 g digestible protein per litre, of a semi-liquid porridge. Microbiological safety is enhanced by biological acidification (lactic acid fermentation) until pH ≤4.5. An evaluation of processing operations, e.g. soaking, germination, roasting, and fermentation is presented and their effect on safety and digestibility of the final product is discussed. Some scenarios are presented for complete processes to obtain shelf-stable, dry powdered formulas that meet the above requirements. Blends of cereals, rootcrops and proteinaceous legumes are prepared and subjected to lactic acid fermentation using a simple enrichment starter to ensure adequate acidification. Enzyme rich flour is used to reduce bulkiness. At small-scale production level, cooking and drying is best done by dry-toasting. Extrusion cooking is a promising technique that can be feasible at medium and larger-scale production levels

Integrated food science and technology for the tropics

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Abacha making qualities of selected cassava varieties

‘Abacha’ of three different thickness, 0.8, 1.0 and 1.6mm was prepared from four varieties of cassava, 91/02324, 97/4779, 98/2101 and NR 87184. The varietal effects on the length of the ‘abacha’ per thickness as well as the yield were analyzed. The HCN, the proximate composition, length of the ‘abacha’ shreds and sensory qualities were evaluated. The effect of drying methods on the quality of ‘abacha’ wasalso determined. Results showed that the proximate composition of ‘abacha’ from the varieties ranged 8.32-8.46% for moisture, 2.38-3.87% ash, 0.54-0.82% fibre, 0.44-0.87% fat, 1.42-1.75% protein, 83.88-85.15% for carbohydrate and 325.39-333.12KJ/100g energy content. Variety 97/4779 had the highest yield. The sun dried‘abacha’ had lower HCN content (8.44-10.00%) than the freshly made ‘abacha’ (15.25-15.95%). For long term consumption of fresh ‘abacha’, the soaking time should be extended beyond 12hrs before washing to prevent HCN toxicity. Sensory evaluation results showed that sun-dried‘abacha’ sample was preferred to oven dried samples. Variety 91/02324 having 0.8mm thickness was preferred in terms of appearance and mouth-feel while 98/2101 of 0.8mm thickness was preferred in taste and general acceptability

A review of rheological properties of high quality cassava flour (HQCF) composites.

Food products development by means of composite flour technology is experiencing a remarkable upsurge globally with the ticking of the clock; thereby inviting a great deal of researchers’ consideration, particularly in bakery foodstuffs and pastries making. The world population is increasing and is projected to be well over eight billion people in the year 2030, with attendant imports of an increased consumption, hence higher demands for processed foods such as bread. In view of the climb in consumption of bread, a higher demand for wheat should be in anticipation. Thus, shrinkage in the global supply of wheat as a resource in the immediate future should be anticipated. This development gives emphasis to the necessity for alternative sources of flour and starch. The attention of this review is directed at the studies of rheological characteristics of composite flour vis-à-vis its consumptions via food products such as bread, biscuits, and pasta. Emphasis is on blends which have high quality cassava flour (HQCF) or just cassava flour as one of the compositing flours with its influence on the sensory and nutritional qualities in addition to its universal approval. In this work, a report has also been given of a study on wheat flour blended in varying proportions with other flours such as those from rhizomes, legumes, fruits and cereals (other than wheat) to create diverse food products. Cassava flour in bread making has been found to be a suitable substitute for encouraging the utilization of a local produce besides reduction of wheat flour imports and upholding the production of high quality cassava flour (HQCF). The development of gluten-free products and fortification of foods have also turned out to be a possibility. Several researchers have developed a range of breads using cassava flour whose properties are akin to those of wheat flour breads. It is promising that the capability of composite flour in bakery and pastry products to retain similar properties to products made from pure wheat flour has been reported. It has also been testified that the use of composite flours has acceptable impacts on the finishing products from the standpoint of functional and physicochemical characteristics as well as healthiness of the end users. Generally, composite flour technology is being regarded as a noble new method for harnessing the benefits in flours that may not unfold unless in composites, which of course, as a matter of fact, will be contingent upon the proportions of blending