The staple food

INTRODUCTION AND OBJECTIVES

Background

Bread has always been considered as the staple food of choice in Northern Africa and it was probably the first ever man produced processed food, and still remains the most universally accepted. It is universally accepted as a very convenient form of food that has desirability to all population rich and poor, rural and urban. Its products and its production techniques vary from country to country. In Libya it making depends on the imported quantities of wheat grains and its flour. This country consequently imports annually about 90% of its needs of wheat grains mainly for bread making and other bakery products from European countries1 (8).

The quality of most of these products between medium to poor and hence affect the quality of the bread. Bread improvers were used in the local market to improve the quality of the flour (Mona 2000). Preliminary studies showed that most of imported flour been highly deteriorated (8, 15). This fact revealed that:

  1. Most of imported flour is less inform of wheat gluten (weak flour - less than 30%). Incomparable to what has been accepted by Libyan quality board (more than 30% for wet gluten).
  2. Most of imported flour in medium in term of gluten strength which is not suitable for bread nither cookies and cakes production.
  3. Because of weakness of flour, most of bakers using chemical improvers which is most of its in out of order due to health concern.

Flour quality varies from time to time. It is for that reason almost impossible to obtain good bread without determining the flour's suitability for bread-making and the using of bread improvers. As well as the quality of different products prepared from wheat depends mainly on the quality of wheat grain. The quality of any kind of wheat grains depends on several milling, chemical, baking, processing and physical dough properties; each is important in the quality of bread (20).

Human beings mastered the use of wheat and the art of bread making thousands of years ago and good bread is not the result of one brilliant mind; it came about by trial-and-error, over the centuries (8).

It is known that bread is one of the major products of baked foods and it is consumed worldwide an essential food in human nutrition.

It is an important staple for human consumption in many countries of the world (2), and it is a good source of energy and contains groups of vitamin B, proteins and minerals which are essential ,it was probably the first ever man produced processed food, and still remains the most universally accepted. Though it is not a perfectly nutritional source of protein, it is nonetheless a principal source of both calories and protein in most countries. Some 70 % of the world's protein supply comes from vegetable sources, 30% from animal sources (15).

The basic ingredients in bread-making are wheat flour, water, salt and yeast (14; 23). Other ingredients which may be added include flours of other cereals, fat, malt flour, soya flour, yeast foods, emulsifiers, milk and milk products, fruit and gluten (11). With appropriate process optimization, breads with acceptable quality can be made with the addition of non-traditional ingredients (22).

Because of the unique structural properties of hydrated wheat protein, bread can be fortified with a wide variety of protein, vitamin, and mineral supplements.

Bread is also a suitable vehicle for uniformal distribution of a nutritional supplement among family {{11 Nowadays, different breads are produced which can be divided into three categories with respect to their specific volume (volume/weight): those with high specific volume such as pan breads, those with medium specific volume such as French and rye breads, and those with low specific volume such as flat breads (Faridi, 1988) {{241}}.

Bakery Products: Bread Cakes And Biscuits etc. are an essential source of nutrients for human . Commercial bread and biscuits contain around 7-8% protein which is low. Most of these products can easily be enriched and fortified at low cost with proteins(Sharma, Saurabh, Manav, & Prateek, 1998) {{220}}.

Currently, the use of additives has become a common practice in the baking manufacturing.

The purposes of their use are to enhance dough handling properties, improve quality of fresh bread and extend the shelf life of bread during storage (8).

The use of Dairy products in the baking manufacturing is not a new, and traditionally they have been used.

Dairy products are used in bread making formulas in order to increase water absorption and to improve dough handling properties and final product quality. They are integrated into bread for their nutritional value and functional properties. Some of that benefits are increased calcium content, protein enrichment and supplementation of the limiting amino acids, lysine, methionine and tryptophan in the fortified bread products (Mulvihill DM ,1992; Cocup RO, Sanderson WB ,1987 ). They can also retard moisture loss or delay the staling, and therefore, extend the shelf life of baked products (Stahel 1983, Dubois and Dreese 1984) {{223}}.

Research Objectives

The general objective was to study evaluate the effects of whey protein concentrate, modified whey protein concentrate and whey-Galactooligosaccharides in comparison with soy protein concentrate as a improvers for soft wheat bread making, particularly, on the final loaf volume and staling rate over various bread storage times, in order to provide guideline information for better use of this proteins. It attempts to advance the improving of soft wheat dough properties in the following ways:

  1. To create a baked products incorporating combination of wheat and proteins concentrates.
  2. To optimize the level of proteins addition to the wheat bread relative to physicochemical properties of the bread.
  3. Compare the qualities of the bread added with whey protein concentrate to those added with Soy protein concentrate.
  4. To investigate the changes in bread firmness and moisture that occur during storage.
  5. The effect of additives on the retrogradation of wheat starch (Differential scanning calorimeter)
  6. To study the effect of moisture on bread firming.
  7. Compare the organoleptic properties of wheat bread by the addition of whey protein concentrate and soy protein concentrate.

Materials and Methods

Collection of Samples

A soft wheat grains were supplied by W. N. Lindsay Ltd, Tranent, Scotland, UK. In Table 1 the The chemical composition of flour used is shown. Instant dry yeast was used due to its stability during storage, as compared with compressed yeast. The yeast samples (Allinson's baking yeast) and the rest of the ingredients were from the commercial market. For the protein treatment tests, protein concentrate samples (WPC , mWPC and WGOS) were kindly provided from Nandi Proteins Limited Company, Edinburgh, Scotland, UK. The chemical composition of WPC, mWPC and WGOS is shown in Table 2.

Milling of wheat

Flour was obtained by milling fifty five samples of the soft wheat in a DLFU-mill from Buhler-Miag (Braunschweig, Germany) according to the procedures approved by the AACC (1983).

The calculation of Percentage of milling yield was done by taking the weight percentage of wheat flour to wheat milled.

Straight flour was obtained by combining all streams. All wheat flour samples were stored at 5C in tightly sealed plastic containers for further analysis.

Analytical Methods

Crude Protein

The percentage of nitrogen in each wheat flour sample was determined by using Kjeldahl's method (AACC, 1983).

Crude Fat

  • The crude fat content was determined according to the instructions given in AACC (1983).
  • Crude Fibre

    The crude fibre was estimated according to AACC( 1983).

    a-amylase activity

    a -Amylase activity was estimated as falling number (AACC, 1983; method 56-81 B).

    Wet and Dry Gluten

    Wet and dry gluten content in flour sample was measured by using hand washing according to standard method, 38-10 (AACC 1983).

    Evaluation of Bread Characteristics

    Blend formation

    Rheological Measurements

    The doughs for the rheological measurements were prepared as for baking experiments but without yeast.

    Farinograph properties

    Water absorption, dough development time and dough stability were evaluated in triplicate with the farinograph by AACC method 54-21 (AACC 1983).

    Baking process

    Preparation of Pan Bread

    Arabic flat Bread

    Arabic bread was done as described by Mona (2000).

    Volume and Specific volume of Loaf

    The rapeseed displacement method as described by Giami et al. (Giami et al, 2004) was used to determine the loaf volume of the bread. Briefly, loaf volume was measured by seed displacement using Sesame in place of rapeseed.

    Packaging Bread

    The packaging methods to keep bread during storage was carried out in this study after bread was taken from the oven (Fig. 1), it was allowed to cool for 1 hr. Then, to minimize loss of water during storage, each loaf was wrapped with two polyethylene bags and stored in a sealed container at 25 C for up to 7 days.

    Bread texture measurement

    Crumb hardness as texture measurement was determined after 1 hr cooling and during storage on the Zwick/Roell type Z010 machine. AACC method 74-09 (1983) was used to measure the hardness of crumb.

    Moisture Measurement of Bread

    The moisture of the crumb was immediately determined after hardness measurements were taken, according to the AACC two-stage moisture procedure 44-18 (1983).

    Results and discussions

    Soft wheat flour Robigus contained 13.4% moisture, 9% protein, and 0.4% ash. The WPC contained 4.5% moisture, 80.1% protein, and 5% ash. The mWPC contained 4.5% moisture, 65.2% protein, and 5.4% ash. The high protein content in WPC indicates that a large portion of minerals and lactose were removed during the concentration process. The solubility of untreated CWPC was 91.1% and decreased to 15.9 and 30.8% after heat treatment and HHP treatment, respectively. The low solubility of WPC treated with either heat or HHP was due to the denaturation of protein in WPC.

    Plan research to second year

    Further experiments should be conducted to study the effect of proteins addition on the shelf life of the bread furthermore to measure the nutritional value of the proteins wheat bread.

    Other future studies of this project include Confocal scanning laser microscopy to visualize the protein and starch in dough, sensory analysis and also the interactions between ingredients in the product.

    Conclusion

    Using of mWPC or W-GOS as dough improvers, improved bread quality better than adding WPC. Both mWPC and W-GOS increased flour water absorption while native WPC had inverse effect. Optimum percentage of mWPC was 5%. With this level, bread had maximum specific volume and had high preference score.

    Acknowledgments

    I would like to thank Dr. Lydia Campbell.

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