Quality Characteristics of Biscuit Produced With Wheat-sweet Potato Composite Flour
Chapter One
Objectives of study
- To know the means of making biscuits from sweet potato flour
- To learn the characteristics of biscuits made from potato flour
CHAPTER TWO
Definition of Composite Flours
Composite flours are quite different from the ready-mixed flours familiar to millers and bakers. Whereas ready-mixed flours contain all the non-perishable constituents of the recipe for a certain baked product, composite flours are only a mixture of different vegetable flours rich in starch or protein, with or without wheat flour, for certain groups of bakery products. This gives rise to the following definition:
“Composite flours are a mixture of flours from tubers rich in starch (e.g. cassava, yam, sweet potato) and/or protein-rich flours (e.g. soy, peanut) and/or cereals (e.g. maize, rice, millet, buckwheat), with or without wheat flour” 24 .
Composition of Composite Flours
The goal of earlier research with composite flours was to save the largest possible percentage of wheat flour in the production of certain baked products. The extent to which wheat flour could be replaced by other vegetable flours naturally depended on the nature of the products to be baked.
Bread and Small Baked Goods
Trials with composite flours with and without wheat flour were carried out for this purpose. The composite flours containing wheat flour usually consisted of 70% wheat flour, 25% maize/cassava starch and 5% soy flour. But there were tests in which the composite flour contained no wheat flour at all – for example 70% cassava flour or starch and 30% peanut and/or soy flour.
pastry goods
In this field the focus of the tests was on producing hard and soft biscuits, with or without the use of wheat flour. As a rule, the composite flour containing wheat consisted of 70 – 80% wheat flour and 20 – 30% soy flour. In cases where no wheat was included, a mixture of 100% sorghum/millet flour or 50% cassava starch, 20% milk powder and 30% soy flour was used.
pasta
In this field the focus of the tests was on producing hard and soft biscuits, with or without the use of wheat flour. As a rule, the composite flour containing wheat consisted of 70 – 80% wheat flour and 20 – 30% soy flour. In cases where no wheat was included, a mixture of 100% sorghum/millet flour or 50% cassava starch, 20% milk powder and 30% soy flour was used.
In this field the focus of the tests was on producing hard and soft biscuits, with or without the use of wheat flour. As a rule, the composite flour containing wheat consisted of 70 – 80% wheat flour and 20 – 30% soy flour. In cases where no wheat was included, a mixture of 100% sorghum/millet flour or 50% cassava starch, 20% milk powder and 30% soy flour was used.
Technical problems at the bakery
In this field the focus of the tests was on producing hard and soft biscuits, with or without the use of wheat flour. As a rule, the composite flour containing wheat consisted of 70 – 80% wheat flour and 20 – 30% soy flour. In cases where no wheat was included, a mixture of 100% sorghum/millet flour or 50% cassava starch, 20% milk powder and 30% soy flour was used. The limit for the addition of cassava/ maize rice to wheat flour for bread and small baked products is at least 50 – 80% wheat flour. The percentage depends on the baking quality of the imported wheat flour concerned. In the case of biscuits it is possible to replace wheat flour completely.
CHAPTER THREE
MATERIALS AND METHODS
Preparation of Sweet Potato Flour
The sweet potatoes tubers were purchased from Apata market in Ibadan and the potato skin were peeled off from the tuber, the edible portion of the sweet potatoes were washed in clean tap water, before they were sliced into pieces and sun dried. After two weeks of sun drying, the dried potatoes chips were milled into sweet potato flour and the sweet potato flour were sieved to obtain fine flour and stored in plastic containers with lids in a refrigerator from where samples were drawn for Biscuits preparation. Wheat flour was purchased from local shop where they are sold and were stored in plastic containers with lids in a refrigerator.
Preparation of Biscuits
CHAPTER FOUR
PHYSICO-CHEMICAL ANALYSIS OF SAMPLES
Bulk density of the flour Samples
The bulk density of the floor samples was determined by Wang and Kinsella method (1976). Sweet potato flour, maize flour, and their blends (10g) each was weighed into 50ml graduated measuring cylinder. The sample was packed by gently tapping the cylinder on the bench top 10times from a height of about 5cm. the volume of each sample was recorded.
CHAPTER FIVE
Discussion of finding, conclusion and recommendations
Findings
There was increase in moisture as more potato flour is added to wheat flour; this result is in agreement with the work of (Khaliduzzaman et al., 2010) when he supplemented wheat flour with 20% potato flour in making biscuits. Carbohydrate value range between 56.52g/100g and 64.75g/100g; the highest value was recorded in 100:0 ratios of wheat-sweet potato biscuit.
Despite the fact that mineral content of raw wheat are higher than mineral content of raw sweet potato, it was observed from the results that the mineral value of calcium, magnesium, potassium, sodium and phosphorus are higher in biscuits made from ratio 90:10, 70:30, 60:40 and 50:50 wheat- sweet potato composite flour than biscuits made from ratio 100:0 of wheat-sweet potato composite flour. These results suggest that biscuit of good mineral content can be produced when wheat flour is substituted with sweet potato flour.
The bulk density is a reflection of the load the samples can carry if allowed to rest directly on one another. The results showed that flour mixture of ratio 100:0 wheat-sweet potato composite flour has higher value (0.9091g/cm3) of Bulk Density, while the lowest value (0.7407g/cm3) of bulk density was recorded in flour mixture of ratio 60:40 wheat-potato composite flour. The particle size and the density of flour or flour mixtures generally affect the bulk density and it is very important in determining the packaging requirement, raw material handling and application in wet processing in the food industry (Adebowale et al., 2008; Ajanaku et al., 2012). Flour of ratio 100:0 wheat-potato composite flour has the highest (2.41g/g) Water Absorption Capacity, and the mixed of ratio 60:40 has the lowest (1.88g/g) Water Absorption Capacity. Flour of ratio 100:0 wheat–sweet potato, has higher affinity for water, which is informed by its lower moisture content 9.34%. This could be indicative of the fact that wheat flour confers high water binding capacity than potato flour, which causes the reconstitution ability and textural properties of dough obtainable from wheat composite flour to be better than that of wheat-sweet potato flour composite. However, wheat-sweet potato flour composites display acceptable binding properties during preparation, which suggest that the combination of wheat-sweet potato composite can be use in making biscuit. The lose structure of starch polymers causes it to possess high water absorption capacity while products with low value indicates the compactness of such product structure.
One of the most important properties that influence quality and aesthetic considerations in the food industry is the pasting property, and they affect texture and digestibility as well as the end use of starch-based food commodities. Peak viscosity which ranged between 366.83RVU to
407.50 RVU is an index of the ability of starch-based fruits to swell freely before their physical break down (Sanni et al., 2006). The Trough value ranges from 236.33RVU to 291.08RVU, with biscuits made from ratio 90:10 wheat-sweet potato flour having the highest value and biscuits made from ratio of 50:50 wheat-sweet potato flour having the lowest value. Trough is the minimum viscosity value in the constant temperature phase of the RVA pasting profile and it measures the ability of the paste to withstand break down during cooling (Adebowale et al., 2012). The highest Break Down Viscosity (89.08 RVU) was recorded on biscuit produced from ratio 50:50 wheat-sweet potato composite flour, while biscuits produced from ratio 100:0 wheat-sweet potato composite flour has the lowest breakdown viscosity (54.67 RVU). The Final Viscosity ranged between 286.92RVU and 329.25 RVU with biscuit of ratio 90:10 wheat-sweet potato composite flour having the highest value and biscuits of ratio 50:50 wheat-sweet potato flour having the lowest value (329.25RVU). Final viscosity is commonly used to define the quality of particular starch-based flour, since it indicates the ability of the flour to form a viscous paste after cooking and cooling (Adebowale et al., 2012). The setback value ranged between 70.33RVU to 107.58RVU.
There was an increase in setback value as the percentage of sweet potato flour increases in the biscuit. The higher the setback viscosity the lower the retro-gradation of the flour paste during cooling and the lower the staling rate of the product made from the flour (Adeyemi and Idowu, 1990). The Peak time is a measure of the cooking time, and it ranged between 7.50min and
8.93 min, with biscuits produced from ratio 90:10 wheat-sweet potato composite flour having the highest value and biscuits made from ratio 100:0 wheat-sweet potato flour having the lowest value of 7.50min. Pasting temperature ranged from 68.35OC to 91.40°C, and the highest pasting temperature was recorded in biscuits made from ratio 90:10 wheat-sweet potato composite flour. Adebowale et al., 2008 stated that a higher pasting temperature is an indication of higher water binding capacity, higher gelatinization tendency and lower swelling property of starch-based flour as a result of high degree of association between starch granules.
The results of Sensory evaluations reveal that biscuits produced from ratio 100:0 wheat- sweet potato composite are not significantly different (p≥0.05) in taste from biscuits made from ratio 90:10 and 70:30 wheat-sweet potato composite flour, but there was significant difference (p≤0.05) in taste between biscuits made from ratio 100:0 and biscuits produced from ratio 60:40 and 50:50 wheat-sweet potato composite flour. The results of the evaluation also reveal that there were no significant (p≥0.05) difference in colour and overall acceptability between biscuits produced from ratio 100:0 wheat-potato composite flour and biscuit made from ratio 90:10, 70:30, 60:40 and 50:50 wheat-potato composite. During evaluation, most of the panelist shown that biscuits made from ratio 100:0 and 90:10 are more acceptable, when they where ask to comment freely on the products, however, no significant differences was seen when the results were analyzed statistically.
Chinma et al. (2012) got a similar result in his sensory evaluation when he used unripe plantain to supplement wheat flour in the production of cookies; these results suggested that wheat flour could be supplement with other staple food samples in the production of biscuits and other baked food.
CONCLUSION
This research work was carried out in order to test for the nutritional, functional and sensory qualities of wheat-potato composite biscuits. The use of potato in supplementing wheat flour in biscuit production has significant benefits in countries where inadequate wheat is grown. Therefore, incorporation of sweet potato flour in biscuit production will reduce the quantity of wheat that will be imported, thereby reducing the cost of production of biscuits. Supplementing wheat with sweet potato flour in biscuits production will reduce over reliance on the use of wheat flour in biscuits production and other baked products, and it will enhance the utilization of sweet potato in the Nigeria. If wheat importation is reduced, and attention is given to potato farming, it will help strengthen the economy of the nation and provide income to farmers. A substantial amount of potato is spoiled and wasted due to inadequate cold storage facilities and insufficient post-harvest handling facilities in many developing countries. The experiments produced biscuits of acceptable Nutritional, Functional and Sensory qualities from all ratios of wheat-potato flour that was used; therefore, these research findings have unveil new windows for further utilization of sweet potato.
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