•Through ingredients•Contamination at manufacture and handling
•Ingredients added to ice cream mix beforepasteurization normally constitute little microbialcontamination except spores.•However microbial analysis is very important inestablishing the quality of ingredients such asmilk, cream, other dairy products, chocolate,cocoa, eggs, emulsifier and other food additives.
SPCColiformYeast & MouldsThermoduric counts.•Presence of higher bacteria in frozen dairyproducts and ingredients are indicationsof improper sanitation and of processing andhandling conditions
• Bacterial contamination varies with raw milkused, separation process• Inadequate refrigerated storage, Long distanttransport• Usually cream contains high bacterial countsthan the milk from which it is made and suchcream may be a single chief source of bacteria inice cream.
• Best ice cream is made from sweet andunneutralized cream which has not beensubjected to microbial action.• Cream with off flavour if used, will bereflected in the finished product
• The important spoilage organism isPseudomonas fragi which causes unpleasanttaste and taints. The spoilage is usually the resultof chemical changes producing rancid and otheroff flavours. Butter should preferably be stored at–18 to –20 c.
Whole milk/Skim milk:High quality is desirable and it should be freefrom toxin producing microorganisms.• Raw milk should have SPC less than2,00,000/ml•Pasteurized milk SPC should be less than30,000/ml
• Skim milk powder may contain number ofBacillus cereus, though not a major health hazardbut the number should be as low as possible.Bacilli reduce methylene blue rapidly and canproduce clotting in milk; they grow at relativelylow temperature. and in extreme cases causespoilage of the mix.
•Sweetened condensed milk (SCM) and Driedmilk (DM): The bacterial standards intended forice cream manufacturing shouldSCM – SPC 500/mlDM - SPC 50,000/ml and Coliform 90/ml•Condensed milk – Should be stored in mannerthat prevent entrance of insects, bacteria andmould spores.•Dry milk – should be stored in reduced humidityand in places of free from insect & dustcontamination.
• high temperature used in processes like refiningand deodorizing processes. They contain almostno moisture and therefore should contain veryfew organisms indeed.
• Granulated sugar and dextrose, should bealmost sterile. Total count in any sugar should notexceed 200/g.• The most common organism present in smallnumber is Yeasts. Sugar contains only smallnumber of bacteria and is of little importance as asource of bacteria in ice cream. Sugar syrupscontain osmophilic yeasts and moulds may growon the surface if contaminated.
• Tests to be performed:Aerobic spore formers –Thermophiles Mesophilic acid producersAnaerobic thermophilic -H2S and non-H2SproducersYeasts and mouldsColiforms.Thermophilic spores –not more than 125/10g - 150/10gYeasts – not more than 10/10gMoulds – not more than 10/10gFlat sour spores - not more than 50/10g
• Used to maintain smooth texture and body bypreventing formation of large ice crystals.• Stabilizers should not present any problem, butgelatin as an animal products, may be a hazard.The common organism in gelatin is aerobic sporeformer.• Tests for stabilizers: SPC, Coliform, Yeast &Mould, Aerobic spore formers which indicatedegree of unsanitary handling.
• Gelatin should be obtained from reputablesupplies and store as cool & dry.• Gelatin - SPC- not more than 10,000/g andYeast & Mould: not more than 100/g Stabilizersare kept dry and properly protected from dust anddirt, the number of bacteria present tend toreduce as a result of death of organisms.
• Very essential when butter, butter oil orvegetable fats are used to provide surface activematerial in place of natural fat globule membrane.• Homogenization reduces fat globule size andincreases surface area which has to be protected.An emulsifier reduces the energy required tomaintain the integrity of fat globules. Assists inobtaining more uniform and large number ofsmaller, air cells.
• Tests:SPC Coliform, Yeasts & Moulds, ß.haemolytic,streptococci, SalmonellaEgg products – SPC should not exceed 10,000/g
Important source of contamination in ice creamas they are added after mix is pasteurized.• Fruits – canned, fresh and frozen and should beof satisfactory in microbiological standardsparticularly canned fruits.• Fresh & frozen fruits – may contain Yeasts. Nutsmay be infected with moulds.Coconuts may be contaminated withSalmonellae. Walnuts-Mould and parasiticinfection
Tests:visual inspection,SPC,Coliform,ß-haemolytic streptococci,Yeasts & Moulds.Canned / fresh nuts are sterilized in ethyleneoxide & CO2 in1:9 or boiling in sugar solution(50%) followed by drying at 2500C for fewminutes.Coconuts should be heat treated whendesiccated
• Careless handling – defects avoided bymaintaining good management control. Alcoholiccolors add only a fewer bacteria. Flavours havelow counts due to presence of alcohol.Tests: Similar to fruits & nuts.