Technology of food product bread

Bread fermentation techniques

1. 1 Pt. RAVISHANKAR SHUKLA UNIVERSITY, Raipur S.o.S in Biotechnology TOPIC : - Technology Of Food Products Bread SUBMITTED BY – P . Sujata M.Sc. 3 rd Sem GUIDED BY : Dr. Shubhra Tiwari

2. Introduction Technology of Bread processing Ingredients of Bread Types of Bread System of Bread Making Bread Making Technologies Bread staling Bread Ropiness Conclusion Reference 2 CONTENT

3. Introduction 3

4. Technology of Bread Bread is the dietary product obtained from the fermentation and the subsequent baking of a dough mainly made of flour and water made in many different ways . Bread is one of the most consumed food products known to humans, and for some people, it is the principal source of nutrition. Characteristics of good bread : External Internal Volume - Fair volume Colour Symmetry of shape – Perfect shape Structure Bloom – Excellent Fermentation Sheen , texture Crust colour - Right baking temperature gives right crust color Flavour and aroma Evenness of bake Crumb clarity and elasticity Cleanliness Moistness 4

5. Ingredients of bread Flour Yeast Sugar Fat Salt Milk Emulsifiers Water Enzymes Mould inhibitor 5

6. Flour Flour is the main ingredient of bread and is produced by milling the grains of wheat. The chief constituents of flour are starch (70%), protein (7–15%), sugar (1%), and lipids (1%). In bread-making from T. vulgare , the quality of the flour depends on the quality and quantity of its proteins. Flour proteins are of two types. The first type of flour which makes up for about 15% of the total is soluble in water and dilute salt solutions and non-dough forming. It consists of albumins, globulins, peptides, amino acids, and enzymes. The remaining 85% are insoluble in aqueous media and are responsible for dough formation. They are collectively known as gluten. It also contains lipids. Gluten has the unique property of forming an elastic structure when moistened with water. It forms the skeleton which holds the starch, yeasts, gases, and other components of dough. Gluten can be easily extracted by adding enough water to flour and kneading it into dough. 6

7. Yeast The yeasts used for baking are strains of Saccharomyces cerevisiae . The ideal properties of yeasts used in modern bakeries are as follows: Ability to grow rapidly at room temperature of about 20–25°C Easy dispersal in water. Ability to produce large amounts of CO2 rather than alcohol in flour dough . Good keeping quality, i.e. ability to resist autolysis when stored at 20°C. Ability to adapt rapidly to changing substrates available to the yeasts during dough making. High invertase and other enzyme activity to hydrolyze sucrose to higher glucofructans rapidly. Ability to grow and synthesize enzymes and coenzymes under the anaerobic conditions of the dough. Ability to resist the osmotic effect of salts and sugars in the dough. High competitiveness, i.e. high yielding in terms of dry weight per unit of substrate used. 7

8. Types of yeast Fresh yeast Soft solid in form Highest moisture content i.e. 67-72% Present in active state Shelf life is 2-3 weeks Active dry yeast Dry and granular form of yeast 6-8% moisture content Must be rehydrated before use Long shelf life, 2- 12 months in refrigerator Instant yeast Also in granular form 4 -6 % moisture content Longest shelf life – more than a year Does not need to be rehydrated Can be added directly to the dough Hence it activates more quickly than active dry yeast 8

9. Sugar To provide carbon nourishment for the yeasts additional to the amount available in flour sugar, To sweeten the bread To afford more rapid browning (through sugar caramelization ) of the crust and hence greater moisture retention within the bread. Sugar is supplied by the use of sucrose and/or fructose corn syrups (regular and high fructose), depending on availability. Shortening (Fat) Animal and vegetable fats are added as shortenings in bread-making at about 3% (w/w) of flour in order to yield increased loaf size, (b) a more tender crumb, and (c) enhanced slicing properties. 9

10. Emulsifiers (Surfactants) Emulsifiers are used in conjunction with shortening and ensure a better distribution of the latter in the dough. Emulsifiers contain a fatty acid, palmitic or stearic acid, which is bound to one or more poly-functional molecules with carboxylic, hydroxyl, and/or amino groups, e.g. glycerol, lactic acid, sorbic acid, or tartaric acid. Sometimes, the carboxylic group is converted to its sodium or calcium salt. Emulsifiers are added as 0.5% of the flour weight. Commonly used surfactants include: calcium stearyl-2-lactylate, lactylic stearate , and sodium stearyl fumarate . Milk Milk used in bread-making must be heated to high temperatures before being dried; otherwise, for reasons not yet known, the dough becomes sticky. Milk is added to make the bread more nutritious, to help improve the crust color, presumably by sugar caramelization , and because of its buffering value. Due to the rising cost of milk, skim milk and blends made from various components including whey, buttermilk solids, sodium or potassium caseinate , soy flour, and/or corn flour. The milk substitutes are added in the ratio of 1–2 parts per 100 parts of flour. 10

11. Salt About 2% sodium chloride is usually added to bread. It serves the foll llowing purposes: (a) It improves taste. (b) It stabilizes yeast fermentation. (c) It has a toughening effect on gluten. (d) It helps to delay proteolytic activity which may be related to its effect on gluten. (e) It participates in the lipid binding of dough. Due to the retarding effect on fermentation, salt is preferably added towards the end of the mixing. For this reason, flake-salt which has enhanced solubility is used and is added towards the end of the mixing. Fat-coated salt may also be used; the salt becomes available only at the later stages of dough formation or at the early stages of baking. Water Water is needed to form gluten, to permit swelling of the starch, and to provide a medium for the various reactions that take place in dough formation. Water with high sulfide content is undesirable because gluten is softened by the sulfhydryl groups. Enzymes Sufficient amylolytic enzymes must be present during bread-making to breakdown the starch in flour into fermentable sugars. Since most flours are deficient in alpha-amylase, flour is supplemented during the milling of the wheat with malted barley or wheat to provide this enzyme. Fungal or bacterial amylase preparations may be added during dough mixing. Bacterial amylase from Bacillus subtilis is particularly useful because it is heat-stable and partly survives the baking process. Proteolytic enzymes from Aspergillus oryzae are used in dough making, particularly in flours with excessively high protein contents. Ordinarily however, proteases have the effect of reducing the mixing time of the dough. 11

12. Mold-inhibitors ( antimycotics ) and enriching additives: The spoilage of bread is caused mainly by the fungi Rhizopus , Mucor , Aspergillus , and Penicillium . Spoilage by Bacillus mesenteroides (ropes) rarely occurs. The chief anti- mycotic agent added to bread is calcium propionate. Others used to a much lesser extent are sodium diacetate , vinegar, mono-calcium phosphate, and lactic acid. Bread is also often enriched with various vitamins and minerals including thiamin, riboflavin, niacin, and iron. 12

13. Types of bread Pan Breads Breads that are baked in pans either open or closed. In North America, Eastern and Western Europe, Australasia, automated or semi-automated equipment , always sold presliced in polyethylene bread bags . 13

14. Flat Breads These are the most widely consumed of all bread types, eaten daily by hundreds of millions of people all over the globe. The single-layered and double-layered types. Single-layered flat breads North and Central Americans: tortilla. Tanoor bread : Middle East, India, and Pakistan. ( wheat flour, soda (sodium bicarbonate), yeast, and water) Sourdough can be used in place of the yeast. Ciabatta : Lean formula sponge dough, usually consisting of wheat flour, water, yeast, and salt. double-layered flat bread : Arabic bread (pita bread) pocket is formed largely by a second proofing step that is not given to single-layered flat breads. The second proof allows the formed dough surface to dry slightly. The resultant dough skin allows the product to balloon during baking, forming the internal pocket. Baking :at high temperatures, normally 400 °C, for short periods of time, 90–100 s. (enhance pocket formation ). 14

15. RYE BRAED R ye : second most common cereal grain used to make bread. R ye : high conc. of pentosans ( xylose and arabinose, 4 to 5 times more than that found in wheat.) M ay have both positive and negative effects. Ha ve high water-binding capacity, decrease retrogradation and delay staling interfere with gluten formation, giving an inelastic dough that retains gas poorly. T he major problem: the rye proteins do not form a viscoelastic dough. ( rye breads: a small loaf volume and a dense crumb texture. ) R ye flour contains more α amylase (excessive starch hydrolysis, poor texture and reduced loaf volume.) The addition of sourdough cultures compensate for these complications. A s the pH decreases the pentosans become more soluble, begin to swell and form a gluten-like network that enhances dough elasticity and gas retention( act like gluten.) A cidic conditions enhance the water-binding capacity of the starch granules, decreases staling . 15

16. System of bread making 16

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18. The straight dough system: In this system, all the components are mixed at the same time until a dough is formed. The dough is then allowed to ferment at about 28–30°C for 2–4 hours. During this period, the risen dough is occasionally knocked down to cause it to collapse. The straight dough is usually used for home bread making. 18

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23. Bread Making Techniques Steps involved in bread making Pre-fermentation (or sponge mixing) Dough mixing Rounding First (intermediate) proofing Molding Second proofing Flavour development Baking Cooling, slicing, and wrapping 23

24. (a) Pre-fermentation (or sponge mixing): At this stage, a portion of the ingredients is mixed with yeast either with or without flour to produce an inoculum . During this procedure, the yeast becomes adapted to the growth conditions of the dough and rapidly multiplies. (b) Dough mixing: The remaining ingredients are mixed together with the inoculum to form the dough. This is the stage when maximum gluten development is sought. (c) Rounding: The dough formed above is cut into specific weights and rounded by machines. (d) First (intermediate) proofing: The dough is allowed to rest for about 15 minutes usually at the previously used temperature, i.e. at about 27°C. This is done in equipment known as an overhead proofer. (e) Molding: The dough is flattened to a sheet and then molded into a spherical body and placed in a baking pan which will confer shape to the loaf. (f) Second proofing: This consists of holding the dough for about 1 hour at 35–43°C and in an atmosphere of high humidity (89–95%). (g) Baking: During baking, the proofed dough is transferred, still in the final pan, to the oven where it is subjected to an average temperature of 215–225°C for 17–23 minutes. Baking is the final of the various baking processes. (h) Cooling, slicing, and wrapping: The bread is removed from the pan, cooled to 4–5°C, and wrapped in waxed paper or plastic bags. 24

25. Dough Mixing Dough mixing is a process in which flour and water are mixed until gluten is developed, a result of the enhanced interaction between dispersed and hydrated gluten-forming proteins. It’s quite different from batter mixing  due to differences in their respective formulations—specifically, the proportion between dry and liquid ingredients. The goal is to: Incorporate air Hydrate dry ingredients Homogenize the dough by evenly distributing all the ingredients Knead the dough Develop the gluten Stages of dough mixing Pick up:  dough is sticky, cold and lumpy. Initial development:  dough gets warmer, smoother and drier. Clean up:  dough is at maximum stiffness and comes together as one cohesive mass. Final development:  Dough is at the correct temperature and handling quality (gluten film is visible, and the dough is ready to be discharged from mixer). Letdown:  The gluten matrix begins to degrade. The dough is too warm and sticky, lacks elasticity and has too much flow. Breakdown:  Dough is beginning to liquefy. At this stage, the dough is not salvageable and cannot be used to make bread. 25

26. Bread leavening Methods of Leavening: Leavening is the increase in the size of the dough induced by gases during bread-making. Leavening may be brought about in a number of ways. (a) Air or carbon dioxide may be forced into the dough; this method has not become popular. (b) Water vapor or steam which develops during baking has a leavening effect. This has not been used in baking; it is however the major leavening gas in crackers. (c) Oxygen has been used for leavening bread. Hydrogen peroxide was added to the dough and oxygen was then released with catalase . (d) It has been suggested that carbon dioxide can be released in the dough by the use of decarboxylases , enzymes which cleave off carbon dioxide from carboxylic acids. This has not been tried in practice. (e) The use of baking powder has been suggested. Baking powder consists of about 30% sodium bicarbonate mixed in the dry state with one of a number of leavening acids, including sodium acid pyrophosphate, monocalcium phosphate, sodium aluminum phosphate, monocalcium phosphate, and glucono -delta- lactone . CO2 evolves on contact of the components with water: partly during dough making, but mostly during baking. Baking powder is suitable for cakes and other high-sugar leavened foods, whose osmotic pressure would be too high for yeasts. However, when using the same amounts, yeasts are vastly superior to baking powder for leavening. (f) Leavening by microorganisms may be done by any facultative organism releasing gas under anaerobic conditions such as heterofermentative l actic acid bacteria, including Lactobacillus plantarum or pseudolactics such as Escherichia coli. In practice however, yeasts are used. Even when it is desirable to produce bread quickly, such as for the military, for sportsmen, and for other emergency conditions, the use of yeasts is recommended over the use of baking powder. 26

27. Factors which effect the leavening action of yeasts The nature of the available sugar: When no sugar is added to the dough, such as in the traditional method of bread-making, in sponge-dough, and some liquid ferments, the yeast utilizes the maltose in the flour. Such maltose is produced by the action of the amylases of the wheat. However, when glucose, fructose, or sucrose are added, these are utilized in preference to maltose. The formation of ‘ Malto-zymase ’ or the group of enzymes responsible for maltose utilization is repressed by the presence of these sugars. Malto-zymase is produced only at the exhaustion of the more easily utilizable sugars. Malto-zymase is inducible and is produced readily in yeasts grown on grain containing maltose. Sucrose is inverted into glucose and fructose by the saccharase of the cell surface of baker’s yeasts. While fructose and glucose are rather similarly fermented, glucose is the preferred substrate. Fermentation of the fructose moiety of sucrose is initiated after an induction period of about 1 hour. It is clear from the above that the most rapid leavening is achievable by the use of glucose. Osmotic pressure: High osmotic pressures inhibit yeast action. Baker’s yeast will produce CO2 rapidly in dough up to a maximum of about 5% glucose, sucrose, or fructose or in solutions of about 10%. Beyond that, gas production drops off rapidly. Salt at levels beyond about 2% (based on flour weight) is inhibitory on yeasts. In dough, the amount used is 2.0–2.5% (based on flour weight) and this is inhibitory on yeasts. The level of salt addition is maintained as a compromise on account of its role in gluten formation. Salt is therefore added as late as possible in the dough formation process. Effect of nitrogen and other nutrients: Short fermentations require no nutrients, but for longer fermentation, the addition of minerals and a nitrogen source increases gas production. Ammonium normally added as yeast food is rapidly utilized. Flour also supplies amino acids, peptides, and thiamine. Thiamine is required for the growth of yeasts. Therefore, when liquid pre-ferments containing no flour are prepared, thiamine is added. Effect on fungal inhibitors (anti- mycotic agents): Anti- mycotics added to bread are all inhibitory to yeast. In all cases therefore, a compromise must be worked between the maximum level permitted by government regulations, the minimum level inhibitory to yeasts, and the minimum level inhibitory to fungi. A compromise level for calcium propionate which is the most widely used anti- mycotic is 0.19% (based on flour weight). Yeast concentration: The weight of yeast for baking rarely exceeds 3% of the flour weight. A balance exists between the sugar concentration, the length of the fermentation, and the yeast concentration. Provided that enough sugar is available, the higher the yeast concentration the more rapid is the leavening. However, although the loaf may be bigger, the taste and in particular the texture may be adversely affected. 27

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29. Dough Divider Dough dividing is a process that divides bulk dough into consistent smaller dough weights. After mixing, dough dividing is the next step in a bread production plant. Dough dividing implies the transformation/portioning of bulk or large masses of dough into countable or single pieces 29

30. Rounding 30

31. Conical rounders The most common type that consists of a cone which is rotated about a vertical axis, with the track of the fixed rounding surface, or runway, located in a spiral pattern about the outside of it. The friction of the dough pieces between the runway and cone surface seals the dough pieces forms their round shape. The cone of this rounder is inverted and has a grooved surface. 31

32. DOUGH MOLDING 32

33.   Sheeter After intermediate rounding , rounded dough pieces are sheeted or gradually flattened through a series of rollers in preparation for final moulding . The sheeter is usually comprised of 2–3 sets (in series) of Teflon-coated roller heads between which the dough piece is passed to gradually flatten the dough piece. Sheeting applies stress forces (pressure) that help degas the dough piece so that large air cells developed during product transfer or intermediate proofing are reduced into smaller ones to achieve a fine grain in the finished product. Roller sets are arranged in such a way that the gap/clearance is reduced gradually as the dough travels through them. This is critical to promote a controlled reduction of dough thickness. It would be impossible to flatten dough pieces in one single step without causing irreparable damage to the gluten and gas cell structure. After passing through the top rollers, the dough piece becomes much thinner, larger, and oblong in shape. The flattened dough exiting the bottom rollers is ready to pass under the curling chain.  Final moulder The thin, flat dough pieces taken from the sheeter are moulded or formed into tight, uniform cylinders of the proper shape and length. The final moulder is, essentially, a forming conveyor which is equipped with 3 parts that define the product’s final dimensions. Curling chain As the dough piece exits the bottom head roller, it comes in contact with the curling chain. This causes the leading edge to slow down and begin curling back on itself. The weight of the curling chain begins the curling of the dough. Its length can be adjusted as needed. When the dough piece exits the curling chain, it is completely rolled-up. Pressure board and side guide bars These parts give the dough piece its final loaf-type or cylinder shape by exerting downward/outward pressure and forcing the dough against side bars. This further de-gasses the dough pieces to form tight, uniform and sealed cylinders. Final moulder adjustments Side guide rails and height of the pressure board of high-speed moulders can be adjusted to allow for a variety of dough piece sizes and lengths. 33

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35. Fermentation Fermentation is an anaerobic biological process that converts sugars and starches into simpler substances. In baking, it causes yeast and bacteria to convert sugars into carbon dioxide, among other things. This is what causes the dough to rise. St arch is converted into sugars by enzyme action. S ugars CO 2 and ethanol A s CO 2 produced, the dough expands and retains it, the skin should remains flexible. R etained gas is equal to (quality of the gluten ) The more retained gas, the more bread volume. 35

36. The temperature = ( T he kind of bread and the breadmaking process (28–30 °C) . T he lower the temperature, the longer fermentation time (2–4 h or 1–1.30 h). The RH :60 and 90%, =( formulations and ferm. temp.) There are two phases in fermentation: Bulk fermentation, first fermentation, or first proof (from final kneading to the dividing of the dough) The main fermentation, final proof, or proving.(from molding to baking) Soft flours ;the fermentation time should be reduced. If the relative humidity is < 75%, the skin of the dough will be very dry and will lose its elasticity. The capacity of dough to withstand excessive mechanical work is called dough tolerance. ( dough that ferment slowly are more tolerant. ) TO MANIPULATE FERMENTATION TIME By amount of yeast: y*t/n=x y: percent yeast used normally t: normal fermentation time n: new fermentation time x: percent yeast for new fermentation time 2% yeast 4 h fermentation To reduce 3 h we need 2*4/3=2.66 % yeast needed 36

37. The aim of the bread fermentation is to enable the dough (bread, pizza, cake….) to rise. When the dough is in a hot atmosphere (30-40 ° C), an alcoholic fermentation occurs as yeast or leaven is added and carbon dioxide is released. The CO 2  bubbles produced, alter the dough structure (reorganization of the gluten network). The dough becomes more elastic, the volume increases, the taste changes and the aromas develop. 37

38. Different fermentation methods commonly used: Direct fermentation: The dough is kneaded, proceeded into a “first fermentation”, weighed, rested, moulded and then fermented very quickly (3-4 hours) and baked immediately. This method produces larger size bread, the crumb is very regular and the crust is thin. However, it has poor shelf life, it dries quickly and tends to soften.   Indirect Fermentation: delayed pointing also called mass proving: The dough is mass stored in dough containers or bowls at 6 ° C for a pointing period from 10 to 48 hours (depending on the yeast quantity). The baker can, for example, knead the dough in the afternoon. Fermentation only takes place at night until dawn. The dough pieces will be moulded and baked available in the early morning.   Indirect Fermentation: the slow proving: The dough is kneaded, pierced (only for a very short time), weighed and then molded. The dough pieces are stored for several hours at a temperature generally between 8 to 15 ° C. Depending on the dose of yeast used and room temperature, the proving time varies. . The dough should be firm. This method of slow proving, allows some freedom for the baker. He can anticipate or delay baking the dough the moment to bake.   Indirect Fermentation: frozen controlled proving: The dough is kneaded, proceeded to first fermentation called “benching” (very short), and divided, formed, rested (short term) and shaped. The dough rising is completely blocked at a low temperature (between +2 to +5 ° C) for 24 to 72 hours. The dough has to be firm. A few hours before baking, the dough must rise in temperature (> 15 ° C). The baker may bake several times during the day.   Indirect Fermentation: frozen pre- proved: The dough is kneaded, proceeded to benching or first fermentation, rested and shaped. Unlike the two previous methods, the baker starts proving of the dough at 25 ° c. When  ¾ of proving time has been reached, the dough is blocked at 4 ° C for several hours (12-20h). This technique allows the baker to hot offer bread to their customers. Depending on demand in the shop, dough pieces are thawed, scored and then baked about 30 minutes later. This method requires a firm dough, rich in yeast and improving agents. 38

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41. Flavor development The aroma of fermented materials such as beer, wine, fruit wines, and dough exhibit some resemblance. However, the aroma of bread is distinct from those of the substances mentioned earlier because of the baking process. During baking, the lower boiling point materials escape with the oven gases. Furthermore, new compounds result from the chemical reactions taking place at the high temperature. The flavor compounds found in bread are organic acids, esters, alcohols, aldehydes , ketones , and other carbonyl compounds. The organic acids include formic, acetic, propionic , n-butyric, isobutyric , isocapric , heptanoic , caprylic , pelargonic , capric , lactic, and pyruvic acids. The esters include the ethyl esters of most of these acids as would be expected in their reaction with ethanol. Beside ethanol, amyl alcohols and isobutanol are the most abundant alcohols. In oven vapor condensates, ethanol constitutes 11–12% while other alcohols collectively make up only about 0.04%. Besides the three earlier-mentioned alcohols, others are n- propanol , 2-3-butanediol, and β-phenyl ethyl alcohol. At least one study has found a correlation between the concentration of amyl alcohols and the aroma of bread. Of the aldehydes and ketones , acetaldehyde appears to be the major component of pre-fermentation. Formaldehyde, acetone, propionaldehyde , isobutyraldehyde , methylethyl ketone , 2-methyl butanol , and isovaleraldehyde are others. A good proportion of many of these is lost during baking. 41

42. Baking Bread is baked at a temperature of about 235°C for 45–60 minutes. As the baking progresses and temperature rises, gas production rises and various events mentioned below occur: At about 45°C,the undamaged starch granules begin to gelatinize and are attacked by alpha-amylase yielding fermentable sugars. Between 50 and 60°C, the yeast is killed. At about 65°C, the beta-amylase is thermally inactivated. At about 75°C, the fungal amylase is inactivated. At about 87°C, the cereal alpha-amylase is inactivated. Finally, the gluten is denatured and coagulates stabilizing the shape and size of the loaf. 42

43. Physical–Chemical Changes During Baking There are three phases depending on the temperature the dough reaches: 1. Oven spring (enzyme active zone) (from 30 to 60 or 70 °C); ( due to 57 % gas expansion, 39 % decrease in gas solubility and 4 % increased yeast activity). 2. Gelatinization of starch (55–60 °C) to no higher than 90 °C. 3. Growing and aroma formation above 100 °C. 43

44. 44 T Y P E S O F O V E N

45. Cooling Bread cooling is a mass and heat transfer unit operation . T he main goal of cooling is to decrease the internal temperature of the baked bread from 93–97°C (200–208°F), at depanning or coming out of the oven, to 32–43°C (90–110°F). This step allows the finished product to achieve optimum keeping quality and comply with legal moisture limit of 38 %. Bread can be cooled either: Manually  by placing on cooling racks after depanning (ambient or natural cooling) Automatically  using racks, trays, or continuous conveyor belts (or spirals in wholesale breadmaking operations). 45

46. Bread cooling time is a function of the size and shape of the loaf as well as the oven baking profile. Denser and bigger pieces require longer cooling times (slowing conveyor speed while  maintaining other cooling variables). Cooling variables that require adequate control include: Cycle time (related to conveyor speed in continuous operations in spiral conveyor coolers) Relative humidity and temperature Air flow (convection cooling) Quality considerations Inadequate cooling can negatively impact the quality of the baked product as well as the overall bakery operation. Effects of excessive or insufficient cooling include: Excessive cooling (overcooling): The internal temperature is too low The finished product is drier and firmer with brittle, harsh eating qualities (crumbly) The dryness and loss of moisture contributes to a faster loaf staling Insufficient cooling ( undercooling ): Bread sidewalls will be weak and may collapse while passing through the slicer Slices will be ragged and may tear due to excessive moisture remaining in the loaf and the crumb being too soft Gumming up of the slicer blades thus increasing downtime Pilling of the crumb Excess moisture due to condensation in the wrapper, thus encouraging mold growth Vacuum cooling It is a relatively new technology which is characterized by its ability to reduce the difference between ambient atmospheric pressure and water vapour pressure. The vacuum system uses pumps which remove the gases and water vapour from the cooling chamber, creating a partial vacuum or zone of very low manometric pressure. This accelerates the vaporization of free moisture from the product. Vacuum cooling is a rapid method that is suitable for products that are unstable and prone to collapse as they cool. Vacuum cooling allows bakeries to avoid the dependence on prevailing atmospheric conditions, achieving consistent results and uniform cooling at all times. Equipment required for this purpose must be isolated and sealed from the surrounding area and may be batch- or tunnel-type. 46

47. 47 Bread Cooling process

48. Packaging 48

49. Staling It is a process that involves loss of aroma , loss of crumb softness , and development of crumbliness. It is a term which indicates decreasing consumer acceptance of bakery products caused by changes in crumb other than those resulting from spoilage organisms . 49

50. Retardation of staling 50

51. Ropiness Bacterial spoilage of bread : initially unpleasant fruity odor, followed by enzymatic degradation of the crumb that becomes soft and sticky because of the production of extracellular slimy polysaccharides Primarily Bacillus subtilis and occasionally Bacillus Licheniformis , Bacillus pumilus , and Bacillus cereus Prevention The bread crumb should have a pH of below 5.2. And after baking the bread should be allowed to cool down as soon as possible. 51

52. Conclusion Food technology permits that consumers have a big variety of foods available and, as consequence, they have a more varied and balanced diet. Perhaps the main advantage of food technology is that after processing foods are safer from a microbiological point of view than fresh or unprocessed foods. The main advantage of novel technologies is that they permit to extend the shelf-life and guarantee safety of fresh foods without affecting taste, appearance and nutritional properties. 52

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54. 54 Thank you