FOOD MICROBIOLOGY
- 1. CONTAMINATION, SPOILAGE & PRESERVATION SUGAR & SUGAR PRODUCTS
- 2. CONTAMINATION • Latin word contaminat = “made impure.” • Contaminate = pollute • Contaminate something = impure or hazardous.
- 3. SPOILAGE • The action or process of spoiling of perishable goods. • Spoiled food = damaged/ injured food undesirable for human consumption • Food spoilage causes:- Physical injury Enzyme activity Microbes
- 4. PRESERVATION • The action of preserving something. • Food preservation – action of preserving food in order to maintain it as desirable for human consumption.
- 5. CONTAMINATION Sucrose Maple sugar • Honey Candy Honey
- 6. SUCROSE
- 7. Contaminating sources • Sugarcane • Soil • Handlers • Transportation • Air • Debris/ fine particles on the sides/ joints of troughs at the plant • Industrial equipments & machines
- 9. Contaminants • Slime producers, like species of Leuconostoc and Bacillus; representatives of the genera Micrococcus, Flavobacterium, Alcaligenes, Xanthomonas, Pseudomonas, Erwinia, & Enterobacter. • A variety of yeast, chiefly in the genera Saccharomyces, Candida, & Pichia. • A few moulds.
- 10. Stages when organism gets added • Bagging of raw sugar • Sugar refining • From equipment • From flume & diffusion battery waste
- 11. Microbial action Cutting of cane Extraction Clarification Result • Sucrose inversion • Sugar destruction
- 12. MAPLE SUGAR
- 14. Contaminants • Enter between its flow & being boiled & concentrated • A moderate amount of growth - improve flavor and color • The sap often stands under conditions that favor excessive growth of micro organisms and hence spoilage. • Mostly psychrotrophic, G - rods + yeasts + molds • Bacterial count - <10,000/ml
- 15. Prevention of contamination • Paraformaldehyde taphole pellet • Plastic tubing
- 16. HONEY
- 19. Contaminats • Streptococci/ enteric bacteria – rare • Common isolates – lysosome + • Antibiotics- streptomycin, neomycin • C. botulinum – infant botulism • Gluconobacter & Lactobacillus – present during maturation of nectar to honey
- 20. CANDY
- 21. Contaminating sources MICROBIAL LOAD – 0-2 MILLION BACTERIA/ PIECE
- 22. Classification of candies & confectionaries • Cold processed • Hot processed
- 23. Result of contamination • Food poisoning outbreaks • Salmonellosis
- 24. SPOILAGE • Osmophilic/ xerotolerant microbes • Principle spoilage flora : Saccharomyces spp. & certain moulds. • Bacterial spoilers – Bacillus spp. & Leuconostoc spp. • Sugar concentration ∞ 1/micrbial load
- 25. SUCROSE • At each processing stage it get more n more purified • Sugar concentration increases – crystallization – sugar crystals + molasses • Purity ∞ 1/micrbial load
- 26. Raw sugar cane juice • Low sugar content • Good source of accessory foods for microbes • Readily deteriorates • Spoilages until clarification Gum/ slime : L. mesenteroids/ L.dextranicum Levan : Bacillus spp. (mostly); yeasts/ molds(rarely)
- 27. Sugar in storage • Liquid sugar :- i. 67 – 72 brix sugar ii. support yeast’s growth (Saccharomyces, Candida & Rhodotorula) & molds from air. • Absorption of atmospheric moisture at surface – microbial growth – product deterioration. Preservation : circulation of filtered sterile air
- 28. Molasses & syrups • Microbial spoilage – not common • Tough to heat sterilize • Canned one’s : spoiler’s osmophilic yeasts • Exposure to air – air left in containers – spoilage before sealing • Acidic one’s – hydrogen swells on storage
- 29. SL. NO. SPOILAGE TYPE CAUSATIVE AGENT 1 Ropy or stingy sap Enterobacter aerogenes (mostly), Leuconostoc (responsible) 2 Cloudy, sometimes greenish sap P. fluorescens + Alcaligenes spp. + Flavobacterium spp. 3 Red sap Colored by pigments of red bacteria, e.g. Micrococcus roseus, /of yeasts / yeast like fungi, 4 Sour sap (a group o spoilages without marked color change but have a sour odor) Variety kinds of bacteria or yeasts 5 Moldy sap Molds
- 30. Honey • ≤ 25% moisture • 70 – 80 % sugar • Sugars : glucose(mostly) & levulose • Ph : 3.2 – 4.2 • Chief spoilers : Zygosaccharomyces, such as Z. mellis, richteri, or nussbaumeri, or Torula (Cryptococcus) mellis. • Penicillium spp. and Mucor spp. have develop slowly.
- 31. Special theories for initiation of growth of yeast/ causes of spoilage of honey • Honey- hygroscopic- surface dilution- yeasts multiplication & adaptation to high sugar concentrations. • Crystallization of glucose hydrate from honey- lowers sugar concentration in solution • Long standing- yeast’s gradual adaption to high sugar concentrations.
- 32. Factors effecting microbial growth in honey • Critical moisture content of yeast – 21% • Degree of sucrose inversion to by bees • Available N content
- 33. Honey fermentaion • Slow, lasts for months • Chief products : CO2, alcohol, & non-volatile acids (give off-flavor) • Usually accompanied by darkening & crystallization
- 37. Candy • Not subject to microbial spoilage - high sugar & low moisture content. • Exceptions - soft fondant/ inverted sugar centered chocolate- burst or explode. • Yeast growth develops a gas pressure - disrupt the entire candy/ push out some of sirup or fondant through a weak spot in chocolate coating. • Often this weak spot is on the poorly covered bottom of the chocolate coating.
- 38. PRESERVATION • Storage conditions: keep out vermin -the sugar remains dry. • Can or sugar beet - stored in a controlled atmosphere. • Fungal growth inhibition by 6% CO2 & 5% O2. • During sugar manufacturing the refining processes reduce microbial load present
- 39. • Chemical preservatives used in sugar refining. • Care to avoid buildup of organisms and their spores during processing. • Numbers may be reduced by irradiation with UV/ heat + H2O2 • Chocolate bursting - prevented by a uniform, thick chocolate coating & use of fondant/ other filling.
- 40. • Sirups and molasses - stored at cool T. • The boiling process (evaporation of maple sap to maple sirup) kills the important spoilage organisms. • Honey crystallization: heat to at least 71 C, hold there for 5 minutes, and cool promptly to 32.2 to 38 C. • Molasses & sirups : high osmotic P (∞ degree of sucrose inversion). Mold growth prevented by complete filling of container & reduced by their periodic mixing.
- 41. REFERENCES • Dennis C. Westhoff, William C. Frazier – Food Microbiology – fourth edition - The McGraw Hill companies – NewDelhi- pg.no. : 187 – 195. • James M. Jay– Modern Food Microbiology – third edition – AVI book publications– usa- pg.no. : 193, 244-245
- 42. HIMA HARIDASAN