Quality Evaluation of Different Wheat Varieties for the Production of Unleavened Flat Bread (Chapatti)

RESULTS AND DISCUSSION

Seven wheat varieties collected from different regions of Punjab were evaluated for physicochemical and rheological characteristics and compared with the specifications for wheat physical quality Pakistan Standards (1996) established by Pakistan standard and quality control authority (Table 1).

Table 1:	Requirements for wheat
Source: Pakistan Standard and Quality Control Authority (1996)

Physical characteristics: Data regarding physical parameters of wheat grains revealed that Shafaq-2006 variety had the highest test weight (81 kg/hl) while Inqulab 91 samples possessed the lowest test weight (77 kg/hl) (Table 2). The comparison of different varieties mean test weight with wheat standards (Table 1) showed that all wheat grains were of premium quality i.e. Pak-I. Test weight is considered as one of the important tool in wheat grading system (Pasha, 2006). It is imperative in the grain trade because most grains are sold at a certain test weight. A sample with a higher test weight may get a good price and vice versa. As regards thousand kernel weight, highest value (41.50 g) was recorded in Shafaq 2006 wheat followed by GA 2002 (40.50 g). Thousand kernel weight as well as test weight is useful index for potential milling yield. The differences observed in test weight and thousand kernel weight among wheat varieties may be due to the differences in the genetic make up of the varieties. However, these differences may be partly attributed due to different growing and environmental conditions prevailed during growing periods (Randhawa et al., 2002). Results are comparable with the earlier findings of Ahmad et al. (2001) who reported thousand kernel weight ranges from 28.81-49.01 for different wheat varieties grown in Pakistan.

In case of foreign matter, wheat grains of GA 2002 had the highest (1.07%) and Shafaq 2006 had the lowest (0.24%) non-edible foreign matter. When compared with wheat specifications (Table 1) it was observed that wheat samples Sehar 2006 and Shafaq 2006 were of Pak-I grade, Inqulab 91, Bhakkar 2002 and Auqab 2000 Pak II whereas GA 2002 samples were of Pak III grade.

Table 2:	Physical characteristics of wheat grains (2006-08)

Inqulab-91 wheat samples possessed the highest (1.14%) and Sehar-2006 had the lowest (0.37%) edible foreign matter. The comparison of edible foreign matter (other food grains) with Pakistan wheat standards (Table 1) revealed Pak-I grade wheat samples. The differences in foreign matter may be due to varied climatic conditions of different locations, harvesting and threshing operations as well as planting time (Anjum et al., 2003). Highest broken/shrunken grains was observed in GA 2002 (1.54%) followed by Bhakkar-2002 (1.36%) samples whereas, Sehar-2006 wheat recorded the lowest value (0.70%). Wheat samples mean comparison with wheat standards (Table 1) confirms Pak-I grade wheat. In case of damaged grains, AS 2002 had the lowest (0.42%) and Inqulab-91 had the highest (0.81%)insect damaged grains, whereas Inqulab 91 had the lowest (0.51%) and Auqab-2000 variety had the highest (0.79%) other damaged grains (fungus/black tipped, heat damaged, immature grains etc). When grand mean of total damaged grains (insect and other damaged grains) of all wheat varieties was compared with wheat standards (Table 1), it was observed that wheat samples in terms of damaged grains were of Pak- II grade. The fungi causing black-tip disease are known to be more active if rains occur during harvest (Rees et al., 1984). Hence, it may be a cause of slightly higher other damaged grains.

Chemical/general characteristics: It is evident from the data on chemical characteristics of whole-wheat flour that mean moisture content of different varieties ranged from 9.11% (Shafaq 2006) to 9.79% (GA 2002) (Table 3). It indicated low moisture wheat samples suitable for storage and would be less prone to microbial attack. Moisture content is dependent on genetic makeup of wheat varieties and is largely influenced by agronomic and climatic conditions (Mahmood, 2004). Ash content of all wheat varieties was found quite close to each other. However, highest ash content was observed in Inqulab 91 (1.70%) while lowest ash was recorded in GA 2002 (1.52%) samples. The ash content of flour is related to the amount of bran in the flour and therefore to flour yield.

As regards protein content, Sehar-2006 had the highest protein (12.78%) followed by Inqulab-91 (12.34%), while GA 2002 (11.19%) wheat had the lowest protein content. The protein content is an important criterion while considering the wheat quality. It is a key factor in determining the suitability of wheat for different products. In many areas of the world it is fundamental criterion for establishing the economic value of wheat. Protein content is an inherent characteristic but the quantity of protein depends on the growing conditions (Kent and Evers, 1994). Variation in protein content among wheat varieties is due to differences in their genetic makeup as well as differences in environmental and production conditions prevailed during growth stages (Randhawa, 2001).

Highest wet and dry gluten content was observed in Sehar 2006 (29.59% and 10.20%) whereas lowest value was observed in GA 2002 (26.06% and 8.42%) samples. The differences in gluten content among different samples may be ascribed to the variation in genetic makeup of wheat varieties, climatic conditions and differences in cultural practices and growth locations (Randhawa et al., 2002).

Table 3:	Chemical/general characteristics of whole wheat flour (2006-08)

Highest protein content of flour is not necessarily indicative of its strongest gluten strength i.e. quantity as well as quality of protein both are important for the evaluation of their end product suitability.

In case of falling number, Bhakkar 2002 had the highest mean falling number (425) and conversely lower alpha amylase activity while Auqab 2000 had lowest mean falling number (374) and therefore higher amylase activity. Alpha amylase activity depends on weather conditions, especially precipitation and mineral fertilizer (Gyiri and Sipos, 2006). Results were in confirmation with the investigations of Pasha (2006) who reported falling number ranged from 243-648 in fifty different wheat varieties during 2004-05.

Farinographic studies: Farinographic studies were conducted to determine the rheological properties of whole-wheat flour (Table 4). Highest water absorption (63.07%) was observed in Inqulab 91 followed by Sehar 2006 (62.33%) while GA 2002 had the lowest water absorption (58.62%). DMR test for water absorption reveals that all wheat flour samples were significantly different from each other except Bhakkar 2002 and AS 2002 which had non-significant differences. Water absorption is considered to be an important characteristic of wheat. Stronger wheat flours have the ability to absorb and retain more water as compared to weak flours. Higher water absorption is required for good chapatti characteristics which remain soft for a longer time (Simon, 1987).

As regards Dough Development Time (DDT), Sehar 2006 had the highest value (5.50 min) whereas Bhakkar 2002 had the lowest time (3.27 min). Higher dough development time reflects strong flour while its lower value is an indication of weak flour. Dough stability of different wheat varieties flour varied from 7.57 min (GA 2002) to 11.62 min (AS 2002). All wheat flours were significantly different from each other (Table 4). It is an indicator of flour strength. Dough stability beyond 10 min may be more suitable to the baker as it can withstand mixing for longer period (Anjum and Walker, 2000).

In case of Tolerance Index (TI), highest value (90 BU) was observed in GA 2002 followed by Shafaq 2006 (71.67 BU) and was significantly different from other flour samples (Table 4). Generally, higher the tolerance index value, weaker is the flour. For softening of dough (SD), Sehar 2006 had the lowest value (43.33 BU), which indicates strong flour since flours that have lower SD are stronger and the ones having higher SD values are weaker. The difference between Shafaq 2006 and GA 2002 was non-significant but were significantly different from other wheat varieties (Table 4).

Differences in farinographic characteristics among different wheat varieties may be due to variations in protein quantity and quality (Rehman et al., 2001). Farinographic results of different wheat varieties were comparable to the earlier findings of Huma (2004).

Sensory evaluation: Chapattis prepared from different wheat varieties flour were subjected to sensory evaluation for colour, taste, flavour, texture, chewing ability and folding ability each year in triplicate and their three years mean scores were calculated (Table 5). Highest mean score for colour (7.80) was obtained by Shafaq 2006 whereas Inqulab 91 got the lowest score (6.20). The low score of Inqulab 91 may be due to high ash content, which affect the colour of chapatti since consumers prefer creamy colour and not dark brown chapatti.

Table 4:	Farinographic characteristics of different wheat varieties (2006-08)
WA = Water Absorption, DDT = Dough Development Time, DS = Dough Stability, TI = Tolerance Index, SD = Softening of Dough

Table 5:	Sensory attributes of chapattis prepared from different wheat varieties (2006-08)
*Means followed by same letters do not differ significantly (p<0.05)

In case of taste, Shafaq 2006 was at the top (7.47) followed by AS 2002 (7.33) and found to be least (6.47) for Bhakkar 2002. Maximum flavor score (7.80) was attained by AS 2002 while Auqab 2000 received the minimum score (6.47). The differences in colour, taste and flavour of all the chapattis were attributed to the differences in hardness/softness of wheat grains and other factors like wheat varieties and milling characteristics of wheat (Farooq et al., 2001). For texture, highest mean score (7.33) was obtained by Auqab 2000 followed by Sehar 2006 (7.20). As regards chewing ability, AS 2002 got the maximum score (7.20) and GA 2002 obtained the minimum score (5.53). A wheaty aroma and taste is desirable with a non-sticky, soft chewing feel in mouth (Dhaliwal et al., 1996). Bhakkar 2002 obtained the least score (5.27) for folding ability whereas AS 2002 received the highest score (6.73). With respect to overall acceptability of chapattis, highest score (7.29) was obtained by AS 2002 and thus regarded as more acceptable than other flour chapattis while lowest score (6.14) was obtained by Bhakkar 2002 thus considered least acceptable.

Conclusion: It was concluded that physic-chemical and rheological characteristics of wheat varieties affect the quality of the end product. Overall, quality of wheat varieties was good and comparable to International standards. Wheat variety AS 2002 was ranked highest and most suitable for chapatti preparation.