Bread spoilage and staling

Types of spoilage, Causes of Bread Staling, How to Prevent Spoilage and Bread Staling

1. Bread Spoilage and Staling Submitted by : HABIB-UR-REHMAN PFTF18M006 Institute of Food Science and Nutrition University of Sargodha, Sargodha

2. Contents Bread Spoilage Types of Bread Spoilage Moldiness Ropiness Chalky Bread Bread Spoilage Bread Staling Types of Bread Spoilage Introduction 1. Moldiness Characterized By Causes of Moldiness Theories explaining bread staling How to prevent Moldiness? Starch Retrogradation 2. Ropiness water migration & Water redistribution Causes of Ropiness Decrease in crumb moisture is caused by How to prevent Ropiness ? Protein-starch interaction 3. Chalky Bread Prevention of staling

3. Bread Spoilage Spoilage of bread  can be caused by bacteria, yeast and molds . Generally, breads  have a relatively high moisture content and water activity between 0.94 and 0.97 at a pH of about 6 with sliced, pre-packed and wrapped  breads  belong to the most susceptible bakery products for mold  spoilage.

4. Types of bread Spoilage Spoilage of bread is usually of two types Moldiness ( the quality of smelling or tasting old or stale or mouldy due to mold growth mustiness , must. staleness - having lost purity and freshness as a consequence of aging .) Ropiness ( Ropiness  in  bread  is usually due to bacterial growth and is considered more prevalent in home made breads .) Chalky Bread ( Another type of spoilage of bread is chalky bread which is caused by growth of yeast.)

5. Causes of Moldiness The molds which are prevalent are  Rhizopuss tolonifer (referred as bread mold), Penicillium expansum , Aspergillus niger . Factors Involved in Moldiness Moisture ( The moisture trapped in the bag is absorbed by the fungus and it grows at a faster rate.) Temperature ( Most moulds grow best between room temperature and 30-37 degrees Celsius. However, it does depend a bit on the type of mould .)

6. How to Prevent bread Mold? Moisture contributes to the faster growth of mold. Hence, do not allow your bread to turn moist. It is always better to preserve the bread that is brought from the store, in its original packaging bag . If you are making bread at home, use ingredients that contain oils, like butter, eggs, milk, etc. This will allow the bread to stay fresh for longer period. Never store the bread at room temperature or in the refrigerator for extended period. Freezing will be helpful if prolonged storage is required .

7. Causes of R opiness The chief causative organism is Bacillus subtilis  or B. licheniformis .  In ropiness , the hydrolysis of bread flour protein (gluten) takes place by proteinases . Starch is also hydrolysed by amylases, which encourage ropiness . The manifestation of ropiness is development of yellow to brown color and soft and sticky surface. It is also accompanied by odor.

8. How to prevent Ropiness ? The bread crumb should have a pH of below 5.2. After baking, the breads should be allowed to cool down as quickly as possible. The storage temperature should not exceed 30°C. If ropiness has been determined in bread, the sourdough proportion in production should be increased for safety reasons.

9. Causes of Chalky Bread Chalky Bread is caused by growth of yeast like fungi  Endomycosisfibuligera  and  Trichosporonvariable . This spoilage is characterized by development of white chalk like spots.

10. Bread Staling Bread staling is a complicated process that involves loss of aroma, changes in mouth feel, 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.

11. Introduction Bread staling is a complex phenomenon that originates from multiple physico -chemical events ( amylopectin retrogradation , water loss and redistribution and gluten-starch interactions and gluten transformations) that are not yet completely elucidated. ( Curti , et al, 2011).

12. Characterized by : It is usually characterized by loss of aroma. changes in mouth feel. development of crumbliness. toughening of the crust. firming of the crumb. loss of moisture and flavor. loss in product freshness.

13. Theories explaining bread staling The main causes of bread staling are thought to be: S tarch retrogradation water migration and redistribution Protein-starch interaction Gluten transformations

14. Starch R etrogradation Retrogradation is a reaction that takes place in gelatinized starch when the amylose and amylopectin chains realign themselves causing the dissolved starch difficult to re-dissolve . Starch undergoes swelling or gelatinization when heated in the presence of water – Starch gelatinization.

15. water migration Water migration and Redistribution The migration of water in cellular solid foods during storage has been found to cause loss of crispness. Migration of water occurs within bread and from bread to the environment causing bread to firm.

16. Water redistribution Water migration and Redistribution When bread is stored with crust. Water migrates from crumb to the crust The crumb firms. Loss of crispiness The crumb moisture content and water activity decreased. Decrease in freezable water 

17. Decrease in crumb moisture is caused by: Incorporation of water into the starch crystalline structure Loss of water to the surrounding environment Moisture migration from crumb to crust reduces the level of plasticizing water of the biopolymer networks and contributes to crumb firmness at longer storage times

18. Protein-starch interaction Bread firmness is thought to result from glucan chains of partially leached amylose and amylopectin attached to swollen starch granules forming hydrogen bonds with other starch granules and, to a smaller extent, with gluten fibrils. The distribution of water is shifted from gluten to starch, thereby changing the nature of the gluten network during starch retro gradation. (Gray & Bemiller , 2003)

19. Gluten transformations Gluten is the composite of a gliadin and a glutenin , which is conjoined with starch in the endosperm of various grass-related grains. There is considerable uncertainty about the role of protein in bread staling. One of the main problems with gluten-free breads is their texture and their rapid staling

20. Gluten transformations High protein breads shows lower extent of retro gradation and hence staling. Waxy wheat flour blends have been also found with the ability to retard staling of breads. Protein is thought to retarded bread staling by diluting starch and hence reducing starch retrogradation . Addition of bacterial protease to sourdough has been found to increase bread firmness and staling indicating that proteins actually are important in retarding bread staling

21.   Prevention of staling Enzymes – Heat stable Alpha Amylases Shortenings Emulsifiers- Surface active agents Reheating - Temperature 70-80 Degrees C Packaging Soy addition Malting and Fermentation Incorporation of high fiber flour