MICROBIAL ANALYSIS OF TOAST BREAD

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PROJECT TOPIC AND MATERIAL ON MICROBIAL ANALYSIS OF TOAST BREAD

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ABSTRACT

The analysis of toasted bread was carried out to determine the microbial load. A total of two sample were collected from Douglas market. The analysis was performed in the microbiology laboratory, Imo State University. From the analysis, the microbial count of the Total Heterophilic bacteria count ranges from 1.2-2.8 X10⁶, Total coliform count ranges from 7.8-9.8 X10⁶, TSC ranges from 1.9-2.3 X10⁶, and Total fungi count ranges from 1.6-1.7 X10⁶. Further identification scheme carried out on microbial isolates showed the presence of five bacteria which are Escherichia coli., Salmonella spp., Bacillus spp., Staphylococcus spp., and Klebisella spp. and three fungi which are Rhizopus spp., Mucor spp., and Aspergillus spp. Toast bread which is a good source of nutrients, however microbial loads above 10⁵ tolerant limits and the presence of coliform calls for concern, adequate hazard analysis and critical control point (HACCP) measures the effective good manufacturing practice (GMP) is imperative in the production of bread.

CHAPTER ONE

1.0  INTRODUCTION/LITERATURE REVIEW

1.1 INTRODUCTION

Bread may be described as a fermented confectionary product produced mainly from  wheat flour, water, yeast and salt by a series of process involving mixing, kneading, proofing, shaping and baking (Dewettinck et al., 2008). The consumption of bread and other baked goods such as biscuits, doughnuts and cakes produced from wheat flour is very popular, but the low protein content of wheat flour, which is the most vital ingredient used for the production of different kinds of baked goods has been major concern in its utilization (Young, 2001).

However, wheat is a good source of calories and other nutrients but its protein is of lower nutritional quality when compared to milk, soya bean, pea and lupin proteins as its protein is deficient in essential amino acids such as lysine and threonine (Bakke and Vickers, 2007; Dewettinck et al.,008; Jideani and Onwubali, 2009). The use of white flour derived from the processing of whole wheat grain, which is aimed at improving the aesthetic value of white bread, has also led to the

drastic reduction in the nutritional density and fibre content when compared to bread made from whole grain cereals (Maneju et al., 2011).Recently, consumers’ awareness of the need to eat high quality and healthy foods – known as functional foods, that is,foods which contain ingredients that provide additional health benefits beyond the basic nutritional requirements, is increasing (Ndife and Abbo, 2009). Therefore, the trend is to produce specialty breads 10 Baba, et al.: Sensory Evaluation of Toasted Bread Fortified with Banana Flour: A Preliminary Study made from whole grain flour and other functional ingredients

known as health breads or functional foods (Dewettinck et al., 2008).

The banana fruit is a healthy, nutritious commodity which contains 74%, 23% carbohydrates, 1% protein and 0.5% fat. Without its peel, it is a good source of Vitamin B6, potassium and fiber. Moreover, it has no sodium and cholesterol and is a great source of Vitamin C and magnesium and contains three natural sugars – sucrose, fructose and glucose giving an instant, sustained and substantial boost of energy (http://www.ffc.agnet.org/library). Potentially, it can be processed and preserved to expand its market value such as, pure from ripe fruits for use in ice cream, yogurt, cake, baby foods and nectar; sliced and canned in syrup for use in fruit salads and as toppings; sun dried banana crispy; and, fermented to produce vinegar and alcoholic beverage. A new product with commercial value is the banana flour which can be used as a mixture for various cakes and breads. But since it does not contain gluten, it could not be used as the main ingredient but rather mixed with wheat flour in the production of quality baked products.

Most Nigerian’s are consuming bread as a traditional food item. Wheat flour is the major component of bread. Since wheat is not a tropical crop, it is imported at high cost to meet the rising trend in demand (Udofia et al.,2013). Efforts of government to embark on local production of wheat have been failing; the situation is not likely to improve on account of unfavorable agronomic conditions of the crop in Nigeria. The presence of gluten and glutenin confers wheat with unique baking properties. Wheat may contain some anti–nutritional factors like phytate and tannins especially if not properly processed (Zharfi et al., 2012).

Bread as a daily food is of high interest, therefore its production and distribution deserves improvement. Based on available data, food fibers are considered useful substances for human consumption (Ndife et al.,2011); therefore nutritional expert try to find appropriate methods of adding fiber to food preparations, especially bread. For instance, in Ghana bakery products are prepared with food fibers, and breads enriched with soluble fibers are very valuable. Banana is a high fiber fruit and its consumption decrease blood cholesterol. Addition of about 300 – 500g/kg freeze dried banana to diet had a reducing effect on cholesterol (www.dietaryfiber.food.com/fiber-rda.php.). In general, the more soluble fiber and protein in a bread formulation, the tendered and more nutritious the bread will be. Mohammed and Jingyuan (2010) opined that plantain flour is rich in some vitamins, minerals, antioxidants, proteins and fibers which can decrease heart disease, blood cholesterol, cancer, diabetes and renal calculus. Fortification of bread with banana flour has been reported to improve other useful properties in bread. This was confirmed by Chong and Noor-Aziah (2008) who reported that addition of fiber such as banana powder (10%) to bread formation enhanced water absorption and lengthened dough mixing time. Zhu et al., (2005) reported that banana starch had high resistance to enzyme activity as well as high viscosity. Aparicio–saquilan et al., (2007) produced cookies containing 15% banana powder and found that these cookies had more digestibility and shelf life than control cookies.

Good bread can be made from dough to which adequate amount of yeast is added. The dough is allowed to ferment and kept at desirable temperature for an appropriate period of time. Unfortunately, in most bakeries recovery defects due to under – fermented dough as well as poor flour quality, leaves no choice than to use chemicals such as soda, blanket (sodium hydrosulfite), extra salt for the reduction of gluten fluidity and increase dough elasticity. This practice has health implications such as and is a cause of stomach trouble, malnutrition, increased blood pressure and allergies (www.dietaryfiber.food.com/fiber-rda.php.). This generally affects sensory qualities and overall acceptability of bread (Eddy  et al., 2007). The major or mandatory ingredients in bread making are flour, water and yeast (Akobudu, 2006; Osuji, 2006). The flour should have good amylase activity, the moisture content should be less than 14% and the colour or appearance should be satisfactory (Giami et al., 2004). Due to the high cost, geographical scarcity and high demand of wheat flour, efforts are being directed towards the provision of alternative source of flour. For example, Eduardo et al. (2013) reported that composite bread can be made by substituting 5, 10, 15, 20 and 30% plantain flour for wheat flour. Sensory evaluation evokes measures, analysis and interpretation of consumers’ responses to products as perceived by senses of sight, smell, touch, taste and hearing. The consumer buys nutrition, convenience, image and functionality in food. Therefore, new products must provide all the responses like or near the older product (Udofia et al.,2013).

1.2 AIM AND OBJECTIVE

Aim

The aim of this study is to isolate and indentify microorganisms find in toast bread

Objective

• To determine the microbial load of the toast bread

1.3 LITERATURE REVIEW

1.3.1 The History of Bread

Recent evidence indicates that humans processed and consumed wild cereal grains as far back as 23,000 years ago in the Upper Paleolithic period. From the Neolithic period 9500BC simple stone mechanisms were used for smashing and grinding various cereals to remove the inedible outer husks and to make the resulting grain into palatable and versatile food.

As humans evolved we mixed the resulting cracked and ground grains with water to create a variety of foods from thin gruel, to a stiffer porridge. By simply leaving the paste to dry out in the sun, bread like crust would be formed.

This early bread was particularly successful when wild yeast from the air combined with the flour and water; this started a fermentation process which slightly raised the crust. These ancient breads would however be unpredictable depending on the type of grain, the flour texture, the liquid, the availability of wild yeast and especially the weather (Diakonou, 1999).

Both simple, yet elusive, the art of controlling the various ingredients and developing the skills, required to turn grain and water into palatable bread, gave status to individuals and societies for thousands of years. The use of barley and wheat lead man to live in communities and made the trade of baker one of the oldest craft in the world. Successful bread making was considered an important life skill for ancient Egyptians who left graphic inscriptions on tomb chamber walls.

1.3.2 Types of Bread

Arepa – Arepa is bread produced in South America. It has a similar texture to a soft tortilla, but is thicker, where tortillas are flat. It is made from maize flour, and frequently used for sandwiches with meat and cheese.

Baguette – Baguettes are a very popular type of French bread, characterized by their long tube-like shape, as well as their crunchy crust and soft interior. Baguettes can be up to two feet long, and are used for a variety of purposes outside of sandwiches.

Challah – Challah is traditionally Jewish bread. It is braided before it is baked, giving it a very unique appearance. It has a sweet flavor, and is typically baked with yeast, eggs, honey, and flour.

Ciabatta – Ciabatta is Italian loaf bread, with dense crumbs and a very hard and crisp crust. It is baked with wheat and often flavored with olive oil, rosemary or other spices, and dusted with flour when it comes out of the oven. Ciabatta is very frequently used for sandwiches, especially Panini, as it toasts particularly well,

Cornbread – Cornbread is made by baking corn that has been ground down into meal. Egg and buttermilk are often combined with the cornmeal before baking, making cornbread very cake-like in texture and taste. Cornbread can be very dense and crumby.

Croissant – Croissants are flaky, buttery, and very rich, and shaped like crescent moons. They are French rolls, made by baking puff pastry and yeast dough together in layers. Croissants are traditionally considered a breakfast pastry, and are often served with coffee in European countries, particularly France. Chocolate croissants are very popular as well; they are baked the same way, but a piece of dark chocolate is placed in the dough first.

Dough – Dough is used to make almost all bread. It is made by grinding grains down into a fine flour, and adding water. It is often seasoned, and leavening is added in order to allow the bread to rise when it is baked.

Dosa – Dosa is native to the southern regions of India. It is very thin and flat bread, and is used to wrap fillings such as spiced vegetables and nuts.

English Muffin – The English muffin is a round yeast roll, often prepared by cooking dough on a griddle. Like a crumpet, an English muffin can be very dense and filled with air pockets. They are most often used as a breakfast roll, particularly as a base for breakfast sandwiches.

Focaccia – Focaccia bread was originally made in Italy. It tends to be relatively flat, as it is not needed before it is baked. It is not an entirely flat bread, because yeast is still one its ingredients, which causes it to rise slightly. Focaccia has a very rich flavor, and retains a lot of moisture, since it is brushed with olive oil before it is baked.

Fruit Bread – Fruit bread comes in almost countless varieties, consisting of dried fruit, and sometimes nuts. One of the most popular fruit breads is banana bread. Fruit bread is prepared very much like a cake, usually in a pan rather than as a freestanding loaf, and the mixture does not rise.

Granary bread – (a registered trademark, owned by Rank Hovis) is made from flaked wheat grains and white or brown flour. The standard malting process is modified to maximize the maltose or sugar content but minimize residual alpha amylase content. Other flavor components are imparted from partial fermentation due to the particular malting process used and to Maillard reactions on flaking and toasting.

Leavening – Leavening refers to the process by which bread is made to rise; this produces a lighter and chewier texture to bread. Leavening is accomplished by adding either chemical agents (such as baking powder or baking soda) or yeast to the dough prior to baking bread.

Marble Bread – Marble bread is made by combining pumpernickel and rye dough, and twisting the two together to create a swirl pattern in the finished product. Marble bread is baked in dense loaves and often used for deli sandwiches.

Paratha – Paratha is an Indian flatbread similar to naan. It is prepared with whole wheat flour, which is then fried in oil. Paratha is frequently served stuff with cheese or vegetables.

Poori – Poori is another Indian bread made with whole wheat flour, combined with salt and water. The mixture is fried in oil, and the finished product looks like a puffy pillow.

Popover- A popover is a roll made by cooking egg batter in muffin tins. The rolls are crispy and light, with a hollow interior. Their name comes from the cooking method, which allows the batter to pop over the edge of the muffin cups.

Potato Bread – Potato bread was originally baked in Ireland, when a large amount of flour was replaced with mashed potatoes before baking bread. Potato bread has a denser texture than other breads, and a unique flavor.

Soda Bread – Soda bread is prepared by substituting baking soda for yeast in a traditional bread recipe. Soda bread is very sweet with a light texture, and is frequently flavored by adding nuts or raisins to the dough.

Sourdough – Sourdough bread is baked with certain bacteria that produce lactic acid and create a sour taste. Sourdough typically has a crispy outer crust and a softer, crumbier interior.

Toasted Bread – A bread that has been browned by exposing to radiant heat.

White bread – Classic white bread has actually been around for a relatively short time, compared to other breads. It is made with bleached, chemically refined white flour, resulting in its white color. Similarly, whole wheat bread is made with whole wheat flour, which is not refined (Osuji, 2006).

1.3.3 Nutritional Properties of Bread

Bread supplies a significant portion of the nutrients required for growth, maintenance of health and well-being. It is an excellent source of proteins, vitamins, minerals, and fiber and complex carbohydrates. It is also low in fat and cholesterol. Bread is quite bulky so it takes longer to digest and is therefore more satisfying and less fattening than the fats, sugars and alcohols commonly consumed in excess. All breads are nutritious, and the differences between them in nutritional value are not significant if we eat a balanced diet ( O’connor, 2012).

Formulation and Bread Making

Professional baker recipes use a notation called baker’s percentages. The amount of flour is usually 100%, and the amounts of the other ingredients are expressed as a percentage of that amount by weight. Measurement by weight is more accurate and consistent than measurement by volume, particularly for dry ingredients. The proportion of water to flour is the most important measurement in a bread recipe, as it affects texture and crumbs the most. Hard US wheat flours absorbs about 62% water, while softer wheat flours absorb about 56%. Common table breads made from this dough‟s result in a fine textured, light bread. Most artisan bread formulas contain anywhere from 60 to 75% water. In yeast breads, the higher the water percentages result in more Co2 bubbles and a coarser bread crumb. One pound (450g) of flour will yield a standard loaf of bread or two French loaves. Calcium propionate is commonly added by commercial bakeries to tetrad the growth of molds (Seiler, 1994).Flour is a product made from grain that has been ground to a powdery consistency. Flour provides the primary structure to the final baked bread. While wheat flour is most commonly used for breads, flours made from rye, barley, maize and other grains are also commonly available. Each of these grains provides the starch and protein needed to form bred. The protein content of the flour is the best indicator of the quality of the bread dough and the finished bread. While bread can be made from all-purpose wheat flour, a especially bread flour, containing more protein (12 –14%), is recommended for high quality bread. If one uses a flour with a lower protein content (9 -11%) to produce bread, a shorter mixing time will be required to develop gluten strength properly. An extended mixing time leads to oxidation of the dough, which gives the finished product a whiter crumb, instead of the cream color preferred by most artisan bakers (Seiler, 2000). Wheat flour, in addition to its starch, contains three water-soluble protein groups (albumin, globulin, and proteases) and two water-soluble protein groups (glutenin and gliadins). When flour is mixed with water, the water-soluble proteins dissolve, leaving the glutenin and gliadin to form the structure of the resulting bread. When relatively dry dough is worked by kneading, or wet dough is allowed to rise for a long time, the glutenin forms strands of long, thin, chainlike molecules, while the shorter gliadin forms bridges between the strands of glutenin. The resulting network of strands produced by those two proteins is known as gluten. Gluten development improves if the dough is allowed to autolyse.

1.3.5 Chemical Composition of Wheat

The composition of the dry matter of wheat varies widely depending on soil, climate and genetic variations between wheat types. Wheat in New Zealand has a protein content that ranges on average from 8% to 13%. It has a high carbohydrate content of about 83% of the weight of a kernel (Ade-Omowaye et al., 2008).

Other components of the wheat grain include bran and germ. Bran, the outer coating or “shell”, is rich in B vitamins and minerals.

The wheat germ or embryo is a rich source of B vitamins, oil, vitamin E and fat. It needs to be discarded during milling because the fat is liable to become rancid during storage. It is still very valuable and is used in many products.

Minerals contained in wheat include calcium, phosphorous, potassium, iron, magnesium and sodium (Winkler and Sarah, 2009).

Vitamins such as thiamine (B1), riboflavin (B2), pantothenic acid, inosotol, P-aminobenzoic acid, folic acid and vitamin B6 are also distributed throughout the wheat grain.

All the nutrients contained in wheat make bread an essential part of the diet. Bread is one of the cheapest, high quality nutritious foods in New Zealand and not only provides many essential nutrients but is also low in fat, cholesterol and sugar (Idolo, 2011).

White bread has approximately the same carbohydrate and protein content as whole meal bread, contains soluble and insoluble dietary fibre, and a good percentage of the whole wheat nutrients. It is made from unbleached flour made from the inner 78% of the wheat grain. If you prefer white bread to wholegrain breads, you can get your extra fibre from other wholegrain foods such as breakfast cereals, whole meal crackers and biscuits (Osuji, 2006).

In New Zealand whole meal bread is made from at least 90% whole meal flour. White flour may be added to whole meal flour to make wheat meal products. It is often added to improve the baking quality of breads made with whole meal flour because of its gluten protein content.

Wheat meal breads are not subject to food regulations and so the quantity of whole meal flour used may vary. Nutritional comparisons are therefore difficult to make (Alex, et al., 2008).

Table1, Comparisons of bread with other commonly eaten foods

The average percentage of our daily nutrient requirements supplied by 100g of any bread show that bread is an excellent source of many nutrients that are necessary for a healthy diet. 100g of bread is 2-4 slices depending on type and slice size.

Table2, Average contribution to the nutritional needs of our diet by 100g of any bread

1.3.5 Preparation of Toast Bread

All ingredients were obtained from local market. Flour blends were baked using the straight–dough method with little modification wheat flour. The baking formula was 500g of flour blend, 9 g of compressed baker’s yeast, 5g of NaCl, 13g of cane sugar, 10 g of vegetable shortening and approximately 280ml of water. All the ingredients were mixed in a Kenwood mixer (ModelA907D) for 3.5min. The dough were fermented for 90min at 28±1°C, then punched, scaled to 250g dough pieces, proofed for 90min at 30°C, 85% relative humidity and baked at 250°C, for 30min. Baked toast breads were ground, screened through a 0.25 mm sieve and used for chemical analyses (Chuchan. et al., 1992).

After preparation of the bread, slice your breads, If you’re using a toaster, set the control for how dare you want the toast to be before you put it in, push the button down and the toast will pop up when it’s ready.  If using the grill, preheat to high. Once it’s nice and hot, put your slices of bread under the grill to toast Keep an eye on it and when you’ve got a good colour, carefully pull them out and flip the slices over with some tongs. Toast on the other side until perfect.

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