BREAD MAKING

1. BREADMAKING

2. Bread is one of the most consumed food products known to humans, and for some people, it is the principal source of nutrition.

4. different from most other food fermentations: -the purpose is not to extend the shelf-life of the raw materials (starting material is much more perishable than the finished product) -none of the primary fermentation end products actually remain in the food product

5. contains carbohydrates, lipids, and proteins, essential vitamins of the B complex and of vitamin E, minerals and trace elements. There are numerous variations of the breadmaking process; tradition, cost, the kind of energy available, the kind of flour, the kind of bread required, and the time between baking and consumption of bread.

6. Principal ingredients Flour The most important characteristics of flour: the quantity and quality of gluten, the water absorption capacity, the diastatic activity. After kneading: cohesive, viscoelastic mass retains the gas formed

7. YEAST • Commercial yeast production in the world: exceeds 1.8 million tons/year. • used by: the baking, brewing and distilling industry • Yeast is also a commercial source of natural flavourings, flavour potentiators and the dietary supplements.

8. first compressed yeasts: in England at 1792 The large-scale commercial production of bread: in the US at 1868, by Charles Fleischmann. yeast strains are developed - to tolerate high sugar - to toleratehigh salt concentrations - to high temperatures used in fermentation

9. Currently: more than 500 species of yeasts, belonging to around 50 genera Saccharomyces: ‘sugar fungus’ S. cerevisiae have been isolated from: breweries, wine, berries, cheese, pear juice, honey, eucalyptus leaves, kefir.

12. Hybrid Strains hybrid yeast strains. rapidly fermenting strains: produce high volumes of CO2 for automated bakeries strains with intermediate activity, for traditional bakeries; and strains which ferment more slowly, for in-store bakeries.

13. Bakers' yeast (S. cerevisiae.) Based on moisture content: compressed (most common), granular, dried in the form of a pellet, instantaneous, encapsulated,frozen, or in the form of a ‘cream.’ Based on maltose adaptation: standard and rapid Tolerance to high osmotic pressure : important in frozen dough.

14. Maintenance of Cultures If used regularly:use agar slopes or broth. slope and broth cultures are subcultured once every 2 months.( contamination risk is high) they are kept at 4–8°C until use.

15. Preservation of Cultures The inclusion of glycerol (5–20%), storage at −20°C are recommended. culture collection centres: extended storage of cultures in liquid N2 at −196°C by lyophilization.

16. Growth Requirements S. cerevisiae is a heterotroph, i.e. requires organic compounds for growth. a mesophile, growing best in the temperature range 25–40°C.

17. Carbon Glucose and fructose are readily utilized, sucrose and maltose are preferred. Other malto oligosaccharides can also be utilized, but less readily. S. cerevisiaecannot utilizepentoses, other hexoses, the disaccharides lactose or cellobiose or the polysaccharides.

18. In industry, the preferred carbon sources are cane or sugar-beet molasses Nitrogen can utilize inorganic nitrogen (ammonium sulphate, ammonium chloride, ammonia. Urea Minerals The major minerals required: phosphorus potassium calcium sodium magnesium sulphur.

19. Oxygen S. cerevisiae possesses a remarkable ability to adapt to varying levels of available O2. very low levels of O2: : shuts off the respiratory enzymes. ( ‘waste’ product is ethanol.) When adequate O2 is available; sugar is converted by the respiratory enzymes to CO2 and H2O

20. Temperature S. cerevisiae has one of the shortest generation times amongst yeasts, 2.0–2.2 h at 30°C. Bakers' yeast production is optimal: at 28–30°C.

21. Cultivation In industry, bakers' yeast is produced in fermentation tanks with a capacity of 200 m3 or more. Tanks, and all connecting tubes, should preferably be made of stainless steel. bubbling compressed air (as a source of O2) into the medium

22. a typical cultivation tank :airlift fermenter. Metabolic heat generation:cooling is necessary. If the depth of the broth>3 m, use of compressed air

23. Yeast broth ; 5 % solid After centrifuge 18% s After rotary vacuum filter 30 %s Compressed yeast 30 % s higher the solid higher the activity

24. Finishing Stages Yeast Cream centrifuged in a continuous centrifuge (with a vertical nozzle) at 4000–5000 g. yeast cream: 20% yeast solids. Yeast cream can be stored at 4°C for a number of days, with good retention of viability.

25. Compressed Yeast from yeast cream by Rotary continuous vacuum filters mixed with 0.1–0.2% of emulsifiers ( monoglycerides, diglycerides, sorbitan esters and lecithin), then extruded cut and packaged ( 500 g) in wax paper or polythene sheet. must be rapidly cooled, and stored at 5–8°C.

26. Active Dry Yeast (moisture content of 4.0–8.5%. ) Active dry yeast is stored at room temp. produce thin strands or small particles,then dried. Generally, a tunnel drier is used, taking 2–4 h with the air inlet temp. at 28–42°C.

27. continuous drying or fluidized-bed drying (airlift drying), is also available. Emulsifiers such as sucrose esters or sorbitan esters (0.5–2.0%) are mixed to facilitate rehydration. Antioxidants (butyl hydroxyanisole(BHA) at 0.1%), added to prevent undesirable oxidative changes. 1 g compressed yeast = 0.4-0.45 g dry yeast

28. Rehydration: X g yeast + 4X g water at 37.8-44.5 C T < 32 C …..or T>46 C The glutothione leaches out of yeast and causes to dough become soft and sticky Cell contents ( a acids, vitamins, nucleic acids, coenzymes,glutothione and inorganic salts) leaches out and fermentative power of yeast decreases. heat resistant strains are used: heat resistant strains generally carries low gassing power.

29. pH very tolerant to fluctuations in pH (2–8), but the optimum pH :4 and 6. the pH of dough is 5

30. Production and Retention of Gas Kneading ; air is incorporated into the dough, and air bubbles are formed. These bubbles contain mainly nitrogen;low solubility in water Yeast cannot create new bubbles

31. The more bubbles: finer the grain. CO2 is produced in the aqueous phase, the pH decreases, and this phase becomes saturated with CO2. the dough is leavened and the newly formed CO2 is retained in preexisting bubbles. the quality of gluten is also very important to retain the gas

32. At the pH of dough, most of the carbon dioxide is present as CO2and a small amount of this as CO32− HCO3−, or H2CO3. Only 45% of the total gas produced is retained at the end of fermentation. (lost in initial fermentation, punching, rounding, molding, and final fermentation. )

33. Salt to provide flavor, influence the rheological properties of dough. Higher concentrations of salt inhibit enzymatic reactions and also inhibit the fermentation. salt used: 1–2% (based on flour weight).

34. Optional Ingredients Fat fat increases the shelf-life, produces a finer grain, yields a greater volume of baked foods (10%). The crust is more elastic and softer. The shortening effect ( film between the starch and protein)

35. The shortening effect is greater for fat with a lower melting point than for harder fats. ( hydrogenated vegetable fats) the use of fat requires less water in the formulation.

36. Sugar promotes fermentation, browning of the crust, sweeter taste. dough more stable, more elastic, and shorter, and the baked goods more tender.

37. Milk and Dairy Products Milk, skim-milk powder, whey containing lactose promotes browning, a softer crust, and a longer shelf-life

38. Oxidants improved gas retention. firmer gluten The time of dough maturation is shorter, the oven spring is greater, the volume is large, The oxidant commonly used is ascorbic acid

39. Enzyme Active Preparations Flours with a low enzyme activity: yields breads that do not brown well,stale rapidly. Add fermentable sugars or enzyme active preparations((malted flour, malt extract, and bacterial or fungal α-amylases).

40. Emulsifying Agents to make bread softer during storage, staling is delayed. monoglycerides , lecithin

41. steps in breadmaking • Ingredients:flour, water, salt, yeast Mixing: • dough mixer continuous

43. Rules for mixers -use 90 % of maximum capacity designated -also don’t go below half of the maximum capacity designated

44. MIXING DOUGH hydration of proteinto form gluten and the spreading of the gluten over the surface of the free starch granules to form a continuous matrix. if excessive amounts of the starch granules are damaged in milling ; sticky dough results

45. Mixing time(↑) = f of T(↑), absorption level(↑), flour strength(↑), salt addition,use of oxidizing agent, reducing agent(↓), enzyme supplementation (↓), mixer design ( mixing bar area↓ )and speed

46. Stages of mixing 1 – uniform blending 2- pick up stage , 3- clean up stage , 4-development stage 5-overmixing ( let down stage)

47. Heat production during mixing: Due to dehydration Frictional heat keep temp of the dough: ( 25.5-27 C) by adding ice use chilled water refrigeration

48. Dough divider : Divide dough volumetrically lubricated with mineral oil to prevent sticking of dough while dividing

49. Dough divider

50. Rounding: Dough with a rotary motion produces a ball-shaped piece with smooth skin. improves the retention of gas. Dough is less viscous. After rounding, dough needs a floortime (2 to 20 min)