THE EFFECT OF AMARANTH GRAIN FLOUR ON THE QUALITY OF BREAD

Abstract

Different levels of amaranth grain flour −0 to 50% (w/w) were mixed with the wheat flour and other ingredients (1% salt, 2.5% fat, 1.5% yeast, 10% sugar and 52–74% water), fermented, molded, pan-proved and baked. The baked products were evaluated for loaf volume, moisture content and sensory qualities (color, odor, taste and texture) and compared with bread made from 100% wheat flour. The water absorption of the composite flour increase with increased in level of amaranth grain flour. The loaf volume index decreased from 3.29 to 1.9 and the moisture content increased from 22 to 42% with increase in amaranth grain flour. The sensory means scores of the odor taste, colour and texture decreased from 6.9 to 4.0, 7.1 to 4.8, 7.1 to 6.8 and 6.9 to 4.7 respectively. Generally, above 15% (w/w) amaranth grain flour, there were significant different (p ≤ 0.05) in the evaluated sensory qualities and the product unacceptable.

INTRODUCTION

Many of the under-utilized food crops indigenous to the third world areas, particularly Nigeria are neglected by researchers and policy makers. They may however be of great potential particularly in improving the quality of our foods, hence the nutrient intake of the populace. Amaranth is in one of the many such under exploited crops which shows promising potential as a global resource supplying nutritious grains as well as tasty leafy vegetables (NRC, 1984).

Cultivation of Amaranths dates as far back as 4000 B.C and was known as the food of the gods. It was believed to have mystical qualities and in consumption provides strength and endurance (Pszczola, 1998). Amaranth grain is reported to contain 11.1% moisture content, 2.5–4.1% ash, 12.5–17.6% protein, 6.3–8.1% fat, 3.6–4.2% crude fibre and 62.17–64% carbohydrate (Singhal and Kulkari, 1988). The starch that makes up the bulk of amaranth flour has extremely small granules (average diameter 1 μm) with a small unique dodecahedral structure and high water absorption capacity (Singhal and Kulkari, 1988).

The nutritional or health promoting ingredients in the grain have stimulated so much interest in the grain in recent times, for example, amaranth contain high content of lysine, an amino acid which is essential to body functions, including growth and maintenance of body and brain cells. It has twice the lysine content of wheat protein, three times that of maize and as much as is found in milk, the standard of nutritional excellence (NRC, 1984; Pszczola, 1998). It also has cholesterol-lowering properties attributed to squalene, dietary fibre, tocotrienols and isoprenoid compounds. Similarly its fibre content has been reported to be three times higher than that of wheat, and has high levels of calcium and iron as well as many other vitamins and minerals (Pszczola, 1998).

Amaranth grain has been researched in several areas including-the nutritive value (Pedersen et al., 1990), potential uses (Bressani, 1988), the protein (Bressani 1989), as supplement to cereals (Pedersen et al., 1987), starch isolation (Yanez et al., 1988), evaluation of whole grain (Sanchez-Marrogum et al., 1986), digestibility and protein quality (Garga et al., 1987) and effect of heat processing (Pant, 1985).

Bread is one of the popular and widely available fast foods in Nigeria, and therefore an improvement in the nutritional content will go along way in enhancing the nutrient intake of the populace. Amaranth grain and wheat composite flour was found suitable for bread manufacture (Adeyemi et al., 1992). However, the effect of amaranth grain flour on the quality of the bread is yet to be evaluated.

The acceptability of any product is a function of its sensory qualities and to some extent its physicochemical properties. The work is aimed at examining the effect of amaranth grain flour on some physical and sensory qualities of composite bread using wheat flour bread as a control.

MATERIALS AND METHODS

Materials

Amaranth (Amaranth cruentus) grain used for this work was collected from the Bauchi State Agricultural Development Authority (BSADA). The wheat flour (Golden Penny), yeast (Ferinipan Instant), baking fat (Holsum – Lever Brother Plc) salt and sugar were purchased from Bauchi main market in Nigeria.

Preparation of Material

Amaranth grain flour-The amaranth grain was cleaned, washed to remove dust and sand, and dried at 50°C (using APV-Cabinet Pilot Drier) for 4 hrs. (to moisture content of 8.9%). The dried grain was milled (Kenwood miller) and sieved (0.4 mm aparture sieve) to obtain amaranth grain flour used in the work.

Preliminary Investigation

The moisture content, protein content and the water absorption capacity of the wheat and amaranth grain flour were determined. Also the water absorption of the composite flour was evaluated.

The moisture content was determined using the FDA (1982) method. Two of the sample was oven dried at 105°C for 3 hrs. and the weight difference determined. The protein content was determined using Pearson (1976) Micro-khejahl method. One of the sample was digested, distilled and titrated against boric acid using bromocresol green and the protein content calculated.

The water-absorption capacity was estimated using Akobundu et al. (1982) method. Two grams of the flour was weighed and 10 ml of deionized water added. The mixture was periodically stirred in a centrifuge tube for 30 mm. The contents were centrifuged for 15 min at 8500 rpm, decanted and the difference in weight of sample estimated as the water absorption capacity.

Production of Amaranth Grain and Wheat Flour Composite Bread

The ‘Straight Dough Method’ as described by Ihekoronye and Ngoddy (1985) and France (1981) and the recipe shown in Table 1 was used in producing the dough. The dough was baked at 200°C in an Air-Rotary BCH oven for 15 mins and allowed to cool to room temperature (30°C).

Table 1. Amaranth Grain and Wheat Flour Composite Bread Recipe

	Samples
Ingredients	A	B	C	D	E	F
^* Wheat Flour (g)	1000	950	900	850	750	500
^** Amaranth Grain Flour (g)	–	50	100	150	250	500
Water (cm^3)	520	545	600	650	715	740
Salt (g)	10	10	10	10	10	10
Sugar (g)	100	100	100	100	100	100
Fat (g)	25	25	25	25	25	25
Yeast (g)	15	15	15	15	15	15

^*Moisture Content 9.4%, Protein Content 9.0%.

^**Moisture Content 10.45%, Protein Content 13.65%.

METHODS

Loaf Volume/Loaf Volume Index

The weight of the bread was determined and the respective volume by seed displacement method. A rectangular wooden box was used. The box was fixed with cleaned millet grain, levelled and poured out. The bread was placed in the same box and filled with the measured millet grain and levelled. The volume of the remaining grains from the same measured grains was taken as the volume of the loaf. The loaf volume index was calculated using the formula:

Moisture Content

The moisture content of the bread was determined using FDA (1982) and calculated on dry weight basis.

Sensory Quality

The sensory evaluation of the samples was carried out for consumer acceptance, and preference using fifteen (15) untrained judges randomly selected (students and staff of Dept of Food Science and Technology, Federal Polytechnic, Bauchi) using a nine (9) point Hedonic Scale (1 and 9, representing extremely dislike and extremely like respectively). The quality assessed include:- colour, taste, odour, texture and over all acceptance. Coded samples of the same size at the same temperature (30°C) were served in a coloured (blue) plate of the same size to judges in each panel cupboard under the florescent light. Only one sensory attribute was tested in one sitting. Data collected were subjected to Analysis of Variance. Unless otherwise mentioned, all the measurements were made in triplicate and the values represent the average of three measurement.

RESULTS AND DISCUSSION

Preliminary Observations

The moisture of the wheat and amaranth grain flour were 9.4% and 10.45% respectively while the protein contents were 9.0% and 13.65% for wheat and amaranth flour respectively. The decrease in the protein content (17.6 to 13.65%) of the amaranth (cultivated in the Nigeria) when compared to the findings of Singhal and Kulkari (1988) could be due to the influence of some environmental and soil factors as observed by Babalola and Babalola (1998).

The moisture content of the amaranth flour was higher that of wheat. This could be due to its extremely small granules and the unique dodecahedral structure of amaranth flour which enhance moisture absorption. Akingbala et al. (1994) observed that smaller sized particules absorbed more water than corresponding larger ones. The water absorption capacity of the wheat-amaranth composite flour increased from 2.55 to 6.65 with increase in percentage of amaranth grain flour as shown in Table 2. The water absorption capacity had a high positive correlation relationship (r = 0.86) with the percentage of amaranth grain flour in the composite flour. The increase in water absorption capacity could be due to the extremely small granules and its unique structure (dodechadral) which encourage water absorption (Singhal and Kulkari, 1988). The high fibre content of the amaranth grain flour (Pszczola, 1998) could also increase water absorption capacity of the flour.

Table 2. Effect of Amaranth Grain Flour on the Water Absorption Capacity of Amaranth Wheat Composite Flour

	Amaranth Grain Flour (%)
Parameter	0	5	10	15	20	25	50	100
Water Absorption Capacity (g)	2.55 ± 0.1	2.59 ± 0.21	2.6 ± 0.18	2.65 ± 0.2	2.67 ± 0.2	2.72 ± 0.15	3.12 ± 0.3	3.65 ± 0.25

Effect of Amaranth Grain Flour on Physical Quality

Loaf Volume Index

The loaf-volume index of the composite bread decreases from 3.29 to 1.91 with increase in the percentage of amaranth grain flours. (0 to 50%) as shown in Table 3. There is a strong but negative correlation relationship (r = −0.92) between the amaranth grain and the loaf volume index of the composite bread. The effect was significant at above 20% added amaranth grain flour P ≤ 0.05. The decrease in the loaf volume index (3.29 to 1.91) with increase in the percentage amaranth baking flour (0 to 50%) could be due to the poor baking quality of the inherent protein content of the flour. This findings agree with the observation of Adeyemi et al. (1992) and Sageheza-Marrogen et al., (1985) that amaranth grain flour lack glutein, the principal protein responsible for proper development of ideal dough in bread production. Low loaf volume index indicated heavy bread, which is branded poor quality.

Table 3. Effect of Amaranth Grain Flour on Physical Properties of Composite Bread

	Amaranth Grain Flour (%)
Parameter	0	5	10	15	20	25	50
Loaf Volume index	3.29 ± 0.2a	3.22 ± 0.7a	3.1 ± 0.6a	3.21 ± 0.9a	2.85 ± 1.5b	1.1c	1.9 ± 0.5d
^* Moisture Content (%)	22 ± 1.5c	30 ± 1.2b	30 ± 1.8b	32 ± 2.1b	38 ± 2.2a	38 ± 2.1a	42 ± 1.6a
^* DWB

^*Average means scores followed with the same alphabet in the same row are significantly different at P ≤ 0.05.

Table 4. Effect of Amaranth Grains Flour on the Sensory Quality of Composite Bread

	Amaranth Grain Flour (%)
Parameter	0	5	10	15	20	25	50
Odour	6.9 ± 0.9 m	6.8 ± 1.1 m	5.8 ± 0.9 m	5.8 ± 0.9 m	5.2 ± 0.6 mn	5.2 ± 0.4 mn	4.0 ± 0.3 n
Taste	7.1 ± 1.2 m	6.7 ± 0.9 m	6.2 ± 0.7 mn	6.0 ± 0.9 mn	5.7 ± 0.6 no	4.9 ± 0.2 p	4.8 ± 0.3 p
Colour (Crumb)	7.1 ± 1.0 m	7.1 ± 1.1 m	6.9 ± 0.9 m	6.8 ± 1.0 m	6.8 ± 0.3 m	6.8 ± 0.1 m	6.8 ± 0.5 m
Texture	6.9 ± 0.9 m	7.1 ± 0.6 m	6.9 ± 0.8 m	5.6 ± 0.8 mn	5.4 ± 0.2 no	5.1 ± 0.4 o	4.7 ± 0.4 p
Overal Accept.	6.6 ± 0.8 m	6.8 ± 0.5 m	6.5 ± 0.4 m	6.5 ± 0.5 m	5.2 ± 0.8 n	4.6 ± 0.6 o	4.0 ± 0.6 p

^*Sample means with the same alphabete(s) in a row are not significantly different at P ≤ 0.05.

Moisture Content

The moisture content increases from 22 to 42% with increase in percentage amaranth grain flour (0 to 50%) in composite bread as shown in Table 3. There is a positive correlation relationship (r = 0.92) between amaranth grain flour and the moisture content of the composite bread. The decrease was not significant at above 20% of added amaranth grain flour, P ≤ 0.05.

The increase in moisture content with increase in amaranth grain flour could be due to the extremely small particles size of the flour and the quality of protein. Extremely small particles enhance absorption of water (Akingbala et al., 1994) and also increase in surface area of protein improves moisture content (Cheftel et al., 1985).

Effect of Amaranth Grain Flour on Sensory Quality

Flavor (Taste and Odor)

The mean score decreases from 6.9 to 4.0 and 7.1 to 4.8 for odor and taste, respectively with increase in percentage amaranth flour (0–50%). The effect was significant at above 15% of added amaranth grain flour. The decrease could be due to unusual flavor of the composite bread as observed in the cause of sensory evaluation. The presence of intrinsic compounds in amaranth, according to Sanicheze Marrogum et al. (1985) and NRC (1984) at high temperature produce a nutty flavor which could be objectionable in some baked products.

Texture

The texture means score of the composite bread decreases from 6.9 to 4.7 with increase in percentage of amaranth grain flour (0–50%) added. The effect was significant at above 10% added amaranth grain flour. The decrease could be due to closed texture as a result of poor rising of the dough prior to baking. The absence of glutin in amaranth flour did affect the proper development of the dough resulting into poor texture bread (NRC, 1984). Also, Singhal and Kulkari (1988) observed that the high fibre content of amaranth grain flour could also affect the texture of product.

Colour

The colour means score decreases from 7.1 to 6.8 with increase in added amaranth grain flour (0–50%). The decrease was not significant, P ≤ 0.05. The non-significant effect could be due to the cream/pale colour of the amaranth grain flour which is similar to that of the whole wheat flour normally used in bread production.

CONCLUSION

Amaranth grain flour can be used up to 15% in production of amaranth grain – wheat composite bread without any significant effect on physical and sensory qualities, and hence the loaves were acceptable to consumers. In this blend the high lysine content of amaranth grain could improve the protein quality of the bread. This is particularly beneficial for infants, children, pregnant and lactating mothers.

Acknowledgments