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 countries ( Gadan).
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 (Mona 2000, Gadan 2005). This fact revealed that:
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).
Most of imported flour in medium in term of gluten strength which is not suitable for bread nither cookies and cakes production.
Because of weakness of flour, most of bakers using chemical improvers which is most of its in out of order due to health concern.
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 (. Finney et al 1987).
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 (Gadan, 2005). 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 (Bakke and Vickers, 2007), 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 (11).
The basic ingredients in bread-making are wheat flour, water, salt and yeast (Martin, 2004; Sluimer, 2005). 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 (Kent, 1983; Sluimer, 2005). With appropriate process optimization, breads with acceptable quality can be made with the addition of non-traditional ingredients (Siddiq et al, 2009). 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 (Gadan, 2005).
The use of Dairy products in the baking manufacturing is not a new, and traditionally they have been used. They 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}}.
Dairy byproduct proteins are considered natural functional additives in the reason of their ability to interact with the starch and gluten network in a dough system and thus behave as improvers of dough, and thus they are used in foods to improve texture, flavor, and color, and to increase protein content{{234}}. Milk proteins have been used in the baking industry to improve protein nutritional value of diferent baked products (Kinsella 1971, Gonzales-Agramon and Serna-Saldivar 1988) {{19}}. Whey contains proteins of high nutritive value (Forsum, E. 1975) {{225}}.
In previous years, whey was used mainly in animal feed or discarded (National Dairy Council, 2003). With advances in technology and during recent years attention has been paid to the use of whey proteins in human nutrition. Thus, because of recent discoveries of functional and bioactive roles for whey, whey and whey components are now viewed as valuable ingredients. Whey in the liquid state has long been known to contain proteins of high nutritional value (Wingerd et al 1970, Ling et al 1961), but their use in human nutrition has been complicated by the high lactose and low protein contents of the liquid whey. However, modern technology has made possible the production of whey protein concentrates (WPC) with a reduced lactose content (O'Sullivan, 1971). Both chemical and biological methods (Forsum, 1974) have revealed that these concentrates have excellent nutritional properties. Moreover, a WPC prepared by gel filtration was recently shown to be more effective as a wheat protein supplement than dried skim milk (DSM) or fish protein concentrate (5). The same type of WPC has also been found to be a valuable ingredient in protein-rich weaning foods (6).
The recognition of whey as a source of unique physiological and functional attributes has increased incorporation of whey and whey components into a variety of foods. Whey protein concentrate (WPC) is high protein, low-carbohydrate ingredients that are currently in demand due to increased awareness of nutrition and alternative methods for weight control. Dairy products, especially whey protein products, contain high concentrations of vitamins and minerals.
The total number of consumers purchasing food products that including whey protein is increasing (Williams, 2001). Whey and its proteins currently are used for a wide range of functional and nutritional properties (Hoch, 1997) {{241}}. They are high nutritional value proteins which are valuable as supplements to poorer quality proteins, cereal proteins {{225}}. This proteins include all of the essential amino acids, and are easily digested {{238}}. Whey protein concentrates (WPC) are ingredients widely used in the food industry in a variety of formulated products, such as bakery products due to the excellent functional properties of their proteins (Kinsella & Whitehead, 1989) {{ 214}}, (Morr, 1992) {{ 214}}. in addition, WPC production represents the best means for the utilization of whey proteins (Morr & Foegeding, 1990) {{ 214}}.
Whey proteins are an important functional component in bread formulations. Important functional properties of the whey protein are hydrophilic, swelling and water retention capacity and its ability to absorb and bind water {{ 222}. Thus, they can be significant functional ingredients, improving crust color, crumb structure and flavor development in bread products, as well as improve the nutritional value. In terms of dough rheology, an increase in the dough mixing properties was reported when whey proteins were added to bread formulations. However, They find limited use during the baking of bread products {{244}}. They enhance crust browning, crumb structure and flavor, improve toasting qualities and retard
staling.{{ 216}}.
Whey proteins can be modified by a variety of physical, chemical, or enzymatic processes {{226}}. Modified whey protein concentrate ( mWPC) is an important functional ingredient having wide range of application in food products {{222 }}.
Galactooligosaccharides (GOS) is one of the commercially produced prebiotic ingredients commonly used in the food industry (Ibilola 2009). Galactooligosaccharides can be naturally found in human breast milk and is structurally composed of β-1-6 galactose and β-1-4 glucose. Commercially available GOS are mixtures of lactose, glucose, galactose and oligosaccharides. They can be produced from lactose which is obtained from whey concentrates by the process of transgalactosylation through the enzymatic action of β-galactosidases; their nutritional, physiological and physicochemical properties make them versatile food ingredients (Mussatto et al, 2007).
Polysaccharides and proteins playing important role in the structure and stabilization of food systems, there is ongoing research to investigate the prospective of their interaction as a biopolymer complex. Protein-polysaccharide interactions depend widely on the intrinsic properties of polysaccharides such as electric charge, molecular weight, branching etc (Narchi et al, 2009).
Hence, this research aims was to improve the quality of bread made from soft wheat by the addition of some protein concentrates to the wheat bread formulation to understand their effect on bread quality
Chapter 3
Objectives
General 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 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.
Specific Objectives
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. To study the effect of moisture on bread firming.
6. Compare the organoleptic properties of wheat bread by the addition of whey protein concentrate and soy protein concentrate.
Chapter 3
LITERATURE REVIEW
Whey
Whey History
Whey is the greenish-yellow colored liquid which is drained off of the coagulated cheese curd during the cheese making process (Smithers et al., 1996). Whey, theoretically
has a bland flavor (Laye et al., 1995) but rapidly oxidizes, forming stale off-flavors (Morr and Ha, 1991). Whey contains nearly half of all solids found in whole milk (Chandan, 1997). The majority of the solids found in whey are proteins, fat, minerals, and lactose (Table 1).
For years, the disposal of liquid whey was problematic and often discharged into local waterways, ocean/seas, and fields, or was used in animal feed (Smithers et al., 1996). Discharging whey into lakes and rivers removed the economic burden of disposing of whey in waste treatment facilities. Over the past few years, the Environmental Protection Act (EPA) has placed restrictions on land-spreading as a method for whey disposal, which is an incentive to find other uses for whey and whey products (Casper, 1999).
Whey cannot be used in liquid form so it is spray dried into whey powder (Smithers et al., 1996). The composition of whey powder can be further altered to concentrate specific whey components. These processes have resulted in various applications of whey making it economically convenient to use whey in human food since it contains a high concentration of protein. A popular but low financial return for manufacturing companies is the use of whey in animal feed.
Whey Production
The U.S. is recognized as the leading whey producer in the world (American
Dairy Products Institute, 1998a). Since the 1970's, whey production in the United States
has more than tripled (American Dairy Products Institute, 1998a). More than one quarter
of the world's whey and lactose is manufactured at over 200 facilities in the U.S.
(USDEC, 2003). The continuing long-term trend of U.S. whey exports attests to the high
quality and increasing use of U.S. whey products. From 1998-2001, total U.S. dry whey
exports grew 46% (USDEC, 2003). The U.S. is the top whey supplier in a large number
of countries where the food and beverage manufacturing sector is dynamic and
innovative. Each year, more than 80 billion liters of whey are produced worldwide
(Smithers et al., 1996). deWit (1998) estimated that 700,000 tons of the true whey
proteins produced worldwide are available for use as ingredients in food. The United
States Export Dairy Council (USDEC, 2003) reported 5.6 tons of whey protein
concentrates exported in 1996 compared to 24.5 tons exported in 2001 (Table 2). The
cost of whey protein varies depending on milk prices. Currently, the demand for a higher
protein, lower carbohydrate diet in the marketplace has further increased whey protein
value. WPC80 (whey protein concentrate 80%) is valued at approximately $2.50/lb
(Davisco Foods International, MN, 2004) and WPI is approximately $4.50/lb (Davisco
Foods International, MN, 2004).
Physicochemical Properties of Amino Acid and Protein
Protein are complex macromolecules that compose of up to several hundreds fundamental units, namely amino acid ( Figure 4), joined together by substituted amide bonds called peptide bonds. Each amino acid contains an amino group (- NH3) and a carboxylic group (- COOH) attached to a central carbon called the alpha carbon. A hydrogen atom and an R -group (or side chain) is also attached to the alpha carbon. Twenty amino acids differ from each other in the nature of the R -group attached to the alpha carbon.
Figure 4 Amino acid
The primary structure is a linear sequence of amino acid connected by peptide bonds (-CO-NH-), formed by the condensation of the amino group of one amino acid and the carboxyl group of another. The covalent linkages can also be formed by disulfide bonds. The organization of the amino acid chain in a three dimensional known as the secondary structure. Example of this structure are the α-helix, β pleated sheet and the collagen triple helix. The structure is stabilized by H bonds between the hydrogen of the NH-group and oxygen of the CO-groups.
Redox Systems in Dough
Redox agents are frequently used in the baking industry to optimize the rheological properties of a dough. Apart from gaseous oxygen, the most important redox agents used by bakers are ascorbic acid, potassium bromate, cysteine, and enzyme-active soya flour.
In wheat flour, peptides and proteins containing thiol and/or disulphide groups, lipids containing linoleic acid or linolenic acid, and also phenolic compounds are particularly suitable to undergo redox reactions. They are considered as reactants for the the agents used during the preparation of a dough. A large number of studies have been directed to define the exact composition of the redox systems and the chemical changes involved and to exolain thier effect on dough rheology and on the baked product.
The texture of the Baked Product
One of the principle aims of the baking process is to product a food with desirable textural attributes. These may vary from hard and crisp to soft and springy. During baking the mechanical properties become very much more solid-like (i.e. much reduced tendency to flow).
Depending on the shape of the foodstuff, the method of baking at the time and temperature of bake there will be a greater or lesser amount of water left in the finished food ( Marston & Wannan 1976., Ginzberg 1969). Studies of the influence of water on mechanical behaviour and texture in baked foods of cereal origin have tended to focus on the lower moisture range (0-15%) where crispness is of major concern and the upper range (25-50%) where bread crumb firmness, springiness, and the origin of staling are of most interest.
Chapter 3
Materials and Methods
3.1. 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.
3.2. 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).
Preparation and tempering at 15% moisture were carried out according to AACC method 26-10A. Milling was according to AACC method 26-31. 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 5°C in tightly sealed plastic containers for further analysis.
3.3. Physical Tests
3.3.1.
Chemical Tests
3.4.1. Crude Protein
The percentage of nitrogen in each wheat flour sample was determined by using Kjeldahl's method (AACC, 1983). A sample was first digested in Kjeldahl's flask containing 30 mL concentrated H2SO4 in the presence of 5 g digestion mixture [K2SO4+CuSO4+FeSO4 (90:10:1)] till digested content attained transparent color. Volume of the cooled digested sample was made up to 250 mL and then distillation was carried out in Kjeldahl's distillation apparatus by using 10 mL diluted digested sample and 10 mL 40% NaOH solution. Ammonia liberated was collected in 10 mL of 2% boric acid solution using methyl red as an indicator. The nitrogen collected in boric acid solution was estimated by titration against 0.1N H2SO4 till end point. Nitrogen percentage was calculated by using following equation.
1 mL of 0.1 N H2SO4 = 0.0014 g of nitrogen Protein
Protein conversion factor for wheat flours was N_5.70 (AACC, 1983).
percentage of wheat flour was calculated by:
% Crude protein = % N x 5.7
3.4.2. Crude Fat
The crude fat content was determined by taking 3 g moisture free flour sample using petroleum ether as a solvent in a Soxhlet Apparatus for 2 to 3 h according to the instructions of the manufacturers and the procedure given in AACC (1983).
Weight of fat (g)
Crude Fat % = ------------------------------ x 100
Weight of sample (g)
3.4.3. Crude Fibre
The crude fibre was estimated by taking 1 g moisture and fat free flour sample and digested first with 1.25% H2SO4 and then with 1.25% NaOH solution. The fiber percentage was calculated after drying (AACC, 1983). The crude fiber was calculated as per expression given below:
Weight loss on ignition (g)
Crude Fiber % = ------------------------------------ x 100
Weight of sample (g)
3.4.4. α-amylase activity
α -Amylase activity was estimated as falling number (FN) (Falling Number AB, Stockholm C, Sweden) using triplicate samples of sieved (180 mm) flour (7 g) with 25 ml water (25 °C) in a viscometer tube fitted with a stirrer and rubber stopper (AACC, 2000; method 56-81 B).
3.4.5. 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).
3.5. Evaluation of Bread Characteristics
3.5.1 Preparation of flour samples
Flour was blended with the additives in different ratios as shown in the table 33. Table 33 Blends of wheat
Table 33. Blends of flour and added ingredients
Sample
Treatment
Control
100% wheat flour
WPC (3%)
97 % WF + 3% WPC
WPC (5%)
95 % WF + 5% WPC
WPC (7%)
93 % WF + 7% WPC
mWPC (3%)
97 % WF + 3% WPC
mWPC (5%)
95 % WF + 5% WPC
mWPC (7%)
93 % WF + 7% WPC
W/GOS(3%)
97 % WF + 3% W/GOS
W/GOS(5%)
95% WF + 5% W/GOS
W/GOS(7%)
93% WF + 7% W/GOS
Gluten (1%)
99 % WF + 1% Gluten
Gluten (2%)
98 % WF + 2% Gluten
Blends of wheat flour were prepared 24 hr before preparation of bread.
3.5.2 Rheological Measurements
The doughs for the rheological measurements were prepared as for baking experiments but without yeast.
3.5.3 Preparation of Bread
AACC method 10-lOB (1983) was used to bake bread, using following formula:
The ingredients were mixed for five minutes by Breville SHM2 Food Mixer fig 3.
The preparation of Arabic bread method used was as described by Quail et al. (1990). Flour 300g, yeast 3g, salt 4.5g, sugar 4.5g were mixed with and without acids. Water (160g) was mixed with the dry ingredients for 6 min. After mixing, the dough was transferred to covered plastic bowl and placed in a proof cabinet, and allowed 60 min fermentation at 30°C.
After fermentation, the dough was scaled off into 60g sections. The pieces were rounded by hand into balls and covered with plastic. The dough rested for 10 min then dough pieces were lightly dusted with flour and flattened by gentle hand pressure and passed through a roll sheeter. The sheeted dough was transferred to stainless steel board and covered with a piece of cloth. Then the dough was transferred for a final proofing of 30 min at 30°C. The dough was baked at 400°C for 90 sec., in a preheated aluminum tray. After baking, the bread was cooled for 1 hr. After that, the loaves were assessed and stored in polyethylene bags for further tests.
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. A 2 L measuring cup box was filled with Sesame seeds and the surface leveled with a ruler. The loaf whose volume was to be determined was weighed and the loaf placed in the 2 L cup. The Sesame from the measuring cylinder was poured over the loaf in the box and leveled. The volume of the spilled Sesame was noted as the volume of the loaf. The specific loaf volume (SLV) of the loaf was calculated as the loaf volume per weight of the loaf (cm3/g).
Specific volume of loaf = V/wt (cm3/g)
All determination was in three replicate.
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.
Fig. 2. Method of Packaging Bread.
Bread texture measurement
Crumb hardness as texture measurement was determined by the compression of two 15 mm thick slices of bread, after 1 hr cooling and during storage on the Zwick/Roell type Z010 machine, using the cylindrical 30 mm probe and expressing the results in newtons. AACC method 74-09 (1983) was used to measure the firmness of bread crumb.
Moisture Measurement of Bread
The moisture of the crumb was immediately determined after firmness measurements were taken, according to the AACC two-stage moisture procedure 44-18 (1983).
Confocal Scanning Laser Microscopy
Confocal scanning laser microscopy (CSLM) was used to visualize the protein and starch in frozen dough. A 65-g frozen dough piece from each of the batches of dough prepared for the baking test was removed from frozen storage after 10 weeks. Disks (≈20 mm diameter, 5 mm thick) were cut from the dough piece with a razor blade and transferred to a cryostat held at -25°C. Sections (15 μm
thick) were then cut and placed on a microscope slide. One drop of Nile blue dye (0.1 % aqueous, w/v) was added to the section and a coverslip placed on top. After 5 min, stained sections were examined using a Zeiss LSM310 confocal scanning laser microscope (Carl Zeiss Ltd., Welwyn Garden City, Herts, UK). Images of representative areas of each sample were taken at Ã-40, 1.3 N.A. Confocal
illumination was provided by a Ne/Ne laser (633 nm laser excitation) fitted with a band pass 670-810 nm filter. The confocal pinhole was set to give an x-y resolution of ≈0.2 μm and an axial resolution of ≈1.0 μm. Projections consisting of a z-series of ≈30 optical sections (overall z-depth ≈50 μm) were acquired.
Data were analyzed according to the procedure described by Gadan (2005).
Future Studies
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.
Flour ( soft wheat) was obtained by milling the wheat on a lab mill (Buhler-Miag Co., Minneapolis, MN). The milling of wheat samples was carried out by following the instructions as described by Williams et al. (1986). ash (AACC method 08-01), 14% MB. The flour moisture was 11.99% measured by oven (AACC method 44-15A).
Whey protein isolate was kindly provided from Davisco
Foods International (BIPRO, Lot No. JE 030-3-420, Le
Sueur, MN). The manufacturer's analysis of WPI was
98.0% protein (dry weight basis), 0.3% fat, 1.7% ash and
4.4% moisture.
Whey protein concentrate (WPC) and additives
Whey protein concentrate was procured from Nandi Company, Edinburgh. The WPC was analysed for moisture, ash, fat and protein content according to AOAC methods (1995).
