MICROBIAL SPOILGE OF CEREALS

HOW MICROORGNISMS SPOIL THE FOOD.

1. Microbial spoilage of cereals : S. CHITHRALEKA 222125013 II BSC MICROBIOLOGY AND DMLT FOOD MICROBIOLOGY

2. Cereals and cereal products ; Cereals and cereals products : grains, Pastes, bread, cakes, flours etc. Harvested grains - several hundred to several thousand bacteria and molds per gram. Cornmeal and flour. Because of incubation, malts contains high number of bacteria. Cereals are often used in the production of various functional foods, such as bread, breakfast cereal, pasta and noodles.

3. CONTAMINATION : SOURCES : The exterior surface of harvested grains retain some of the natural flora. Environment - air, soil, water, animals. Others - shipping containers and processing equipment. Wheat flour contains a few hundred to a few thousand bacteria per gram, 20-30 bacillus spores per gram and 50-100 molds per gram. Bacillus spores, Coliform bacteria, Micrococcus, Sarcina, Alcaligenes and Serratia. Wet mash grains – acid fermentation by lactic acid and Coliform bacteria – alcoholic fermentation by Yeast.

4. SPOILAGE OF CEREALS ; Major Factor’s of spoilage : Microbial content, moisture level above 12-13 percent, physical damage and Temperature. Common species of molds : Aspergillus, Penicillium, Mucor, Rhizopus and Fusarium. Species of Fusarium and Penicillium are dominant one . Molds produce mycotoxins. Little moisture content – Molds High moisture content - Yeast and bacteria ( Acetobactor species, Bacillus, Lactis and Coliform and Micrococcus. Cause flour dough to develop an odour of acetic acid and esters.

5. PRESERVATION : S torage temperature : 4.4 to 7.2c is recommended for the dry products. Scouring & washing : remove some microorganisms. Milling : most of the microorganisms are removed with the outer portions of the grains during the milling processes especially bleaching reduce no. of organisms.

6. METHODS OF PRESERVATION : Asepsis : improperly sanitized equipments - rope bacteria and the acid –forming bacteria - sourness of dough. bread ,cakes and other baked products may be subject to spoilage by molds should be protected against contamination by mold spores . Mold Spores – Aspergilli, Penicillia, Alternaria, Cladosporium and other genera. Use of heat : the complete baking process destroys all the bacterial cells, yeasts ,mold spores but not spores of rope –forming bacteria.they can survive during heat so unbaked products are kept for short period or kept cool during longer storage of time. Use of low temp. :baked products should be kept under cool conditions or refrigerated in home for the prevention of food spoilage. These can be stored for months in the frozen conditions.

7. Use of chemical products : Sodium and calcium propionate , sodium diacetate and sorbates are used extensively .acidification of dough with acetic acid has been used to combat rope. Use of irradiation : ultraviolet rays have been to destroy or reduce numbers of mold bacteria in dough and proof rooms, on the knives of slicing machine , on the surface of breads ,cakes . ionizing radiations , gamma and cathode rays have been applied experimentally for the preservation of baking goods.

8. Bread spoilage ; Spoilage of bread can be caused by bacteria, yeast and molds. High moisture content And water between 0.94 and 0.97 PH of about 6 with sliced, pre packed and wrapped breads belong to the most susceptible bakery products for mold spoilage.

9. Types of bread spoilage ; Two types : Moldiness Ropiness Another type : Chalky bread

10. BREAD MOLD ; MOLDINESS : The quality of smelling or tasting old or stale or moldy due to growth mustiness, must. Causes : The molds which are prevalent are Rhizopus tolonifer , Penicillium , Aspergillus Niger. Factor’s involved in Moldiness : MOISTURE – The moisture trapped in the bag is absorbed by the fungus and it grows at a faster rate. TEMPERATURE – Most molds grow best between room temperature and 30-37 degree Celsius. However, it does depend a bit on the type mold.

11. PRESERVATION ; Do not allow your bread turn moist. Preserve the bread in its original packaging bag. Use ingredients that contains oil like butter, eggs, milk etc. ( Homemade ) Freezing Will be helpful if prolonged storage is required. Don’t store in room temperature and never keep in refrigerator for extended period.

12. ROPINESS OF BREAD ; Ropiness in bread is usually due to bacterial growth and is considered more prevalent in home made breads. caused by amylase production of certain strains of Bacillus subtilis (B. Mesentericus). Caused by Bacillus subtilis, Licheniformis and other species. First odour is evident, then discolouration and finally softening of the crumb with stickiness and stringiness . Capsultion of Bacillus the ropiness is formed. Yellow to Brown in color which is soft and sticky.

13. PREVENTION : PH Below 5.2 After baking cool down asap. Storage temperature should not exceed 30°C. Sourdough proportion should be increased for safety reasons.

14. CHALKY BREAD ; Chalky bread is another type of spoilage of bread which is caused by growth of yeast. Chalky bread is caused by growth of yeast like fungi Endomycosisfibuligera and Trichosporon variable. This spoilage is characterised by development of White chalk like spots.

15. RED BREAD ; Red bread is caused by pigmented growth of Serratia marcescens . Molds such as Neurospora sitophlia and Geotrichum aurantiacum can also cause red coloration.

16. Bakery Products ; Cakes of all types rarely undergo bacterial spoilage due to their unusually high concentrations of sugars , which restrict the availability of water. The most common form of spoilage displayed by these products is moldiness. Common sources of spoilage molds are any and all cake ingredients, especially Sugar, nuts , and spices . Although the baking process is generally sufficient to destroy these organisms, Many are added in icings , meringues , toppings , and so forth. Also, molds may enter baked cakes from Handling and from the air. On some fruitcakes, growth often originates underneath nuts and fruits if they are placed on the surface of such products after baking. Continued growth of molds on breads and cakes results in a hardening of the products.

17. Growth of molds on the surface of cakes is favored by conditions of high humidity.

18. BREAD STALING ;

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