Dairy Products

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  • Processes used to produce
    • Cheese
      • Made from milk
      • production depends on a number of biological reactions
      • Cheddar cheese manufacture
        • Pasteurized milk placed into stainless-steel vat with outer water -jacket
          • Lactic acid forming bacteria is added with colouring
            • Lactococcus cremoris and Lactococcus Lactis is used
        • Care taken to prevent 'phage' attack as the starter will be inactivated and cheese will be impossible to produce
      • Harder cheese produced by heating curd to higher temperature, cutting finer in milling and applying higher pressure in moulds
      • Soft cheese use different mould, penicillium camembert which produces a white growth
        • shallow moulds and rubbed with salt which allows mould to grow
          • Enzymes from mould act on curd to soft and creamy texture
        • Shelf life is shoft
      • Processed cheese
        • made by emulsifying cheese with green cheese with emulsifying agents (salt, sodium and potassium phosphate and calcium) and water
          • Chopped into small pieces, heated and mix with green cheese, water and emulsifier
            • wrapped metal foil, heating process kills organisms
    • Dried Milk
      • Milk is 87% water
      • Little loss of the nutritive value if done correctly
        • if over heated - vitamin loss, protein damage and encourage browning by the non-enzymic Maillard reaction
          • lactose (reducing sugar) and amino acid lysine have be apart of the cause of browning
        • fine powders - float of surface of water, have poor dispersability and poor wettability
          • Instantisation - the powder is slightly re-wetted so it clumps together. Act like a sponge and absorb the water and disperse in it rapidly
      • must be kept away from moisture and air
        • if moisture level rise to 5% the Maillard reaction take place - white to cream to light brown
      • fat in whole milk powder is liable to oxidative rancidity fairly rapidly (packed without O2). Shorter shelf life that Skimmed
      • Filled milk - skimmed milk with added vegetable oil, then homogenized and dried. Keeps better than whole milk powders
      • Methods
        • used to be made by a roller dryer. the drier consists of a hollow drum, internally heated by steam to which a film of milk adheres and as the drum roatoes the milk dries to powder.
        • Spray drying (newest) produces better solubility, colour and flavor. Milk is concentrated in the evaporator and sprayed whilst still hot (80C) into a chamber where spray meets a blast of hot air (180C) and dries instantly
    • Evaporated and condensed milk
      • Evaporated milk
        • evaporating water from milk to about 70%
        • to improve granular texture sodium citrate, disodium phosphate or calcium chloride is added
        • highly perishable
        • must be homogenized and sealed into cans and heat processed in retorts at 121C for 14mins
      • Condensed Milk
        • Sweetened
        • depends on its sugar content for preservation
        • first pasteurized the goes straight to evaporator
        • sugar syrup added (60-65% sucrose) and whole milk is concentrated under vacuum at 50-55C
          • then cooled and agitated. small crystals added to ensure rapid crystallization of lactse
            • poured into sterilized cans and sealed without further treatment
    • Skimmed milk
      • all fat removed (0.1%)
        • remove fat soluble vitamins so no used to feed babies
      • use a centrifugal seperator
    • Yoghurt
      • milk, concentrate or with added milk powder
        • Acidity and flavor due to growth of micro-organism.
          • Lactobacillus delbreukii
          • Streptococcus thermophiles
            • Equal amounts otherwise bitter/too acid product will result
              • Lactobacillus delbreukii
      • more protein, thiamin and riboflavin than milk
      • types of yoghurt
        • 'Set yoghurt' - fermentation allowed to take place in container which sold
          • mix incubated at 44C for 1.5 hrs then poured into containers - kept warm until yoghurt has fully coagulate. Then cooled to 5-8C consumed in 14 days.
        • 'Stirred yoghurt' fermented in bulk then packed
          • continuous manufacture, incubation at slightly lower temps, so yoghurt becomes thicker. continuous stirring allows no curd formed. fruit and syrup metered into containers then yoghurt mix, cooled and stored.
        • Frozen Yoghurt
          • 'bio' yoghurt claim health advantage wiuth organism Bifidobacteriubifidum which helps stomach problems by colonsing the gut. also produced acetic acid as a flavouring agent and ferments a milder, creamier product.
      • ingredients
        • Whole milk, skim milk, evaporated milk, dried milk, stabilizers and thickeners, fruit flavors, colors and sugar.
          • sugar, stabilizers, colors and flavors-  blend into milk base
        • Low fat yoghurt - fat separated from the milk using a Centrifugal separator
        • Mix is homogenized then pasteurized at 90C fro 30mins or HTST to kill micro-organisms
          • mix cooled to 44C
    • Icecream
      • Emulsion of fat in a solution made up of colloidal and true solutions.
      • Contains very small crystals of ice, air sacs, fat globules, colloidal suspension of casein, stabilizing agents, flavours, colour and sugar solution.
      • Types of Icream
        • Soft ice cream
          • made locally in small batches
          • stabilizers and emulsifiers used, including gelatin, alginates, modified celluloses, carrageen's, pectin's and various gums
            • prevent formation of large ice crystals during freezing = only small crystals
            • Stabilizers give body and improve melting resistance, good texture
          • 11% Skim milk powder, 6% Fat (Veg), 14% Sugar, 1% Stabilizer, 68% Water, Flavoring and Colouring
            • mix together and homogenized then pasteurized. Air whipped into ice-cream as it is frozen (-5C)
          • Less air mixed into product and only increases volume by 50% compared with Hard icream
        • Both should not have more than 15% sugar content as may crystallize out
        • Hard Ice Cream
          • 10% Skim milk powder, 12% Fat (Veg, butterfat), 12% Sugar, 1% Stabilizer, 63% Water, Flavouring and colouring
          • 8% Fat used, anymore and becomes very heavy
          • During freezing, stirred vigorously to incorporate more air than soft icecream
          • ice cream cut into blocks and wrapped then hardened at -40C
        • Water used must be warm to aid dissolution and dispersion of ingredients
        • Homogenized and pasteurized then frozen
      • Sugar content should not exceed 15%
        • may crystallize

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