UPMSP Vocational Dairy Technology key terms

The amount of acid in a milk sample measured by titrating with standard alkali to a colour endpoint, expressed as percent lactic acid; it indicates freshness and bacterial souring.

A rapid quality test in which methylene blue dye is added to milk and the time taken to lose colour shows the level of microbial activity and keeping quality.

A laboratory method that counts viable bacteria in milk grown on nutrient agar under set time and temperature, giving a colony forming unit value per millilitre.

A test that estimates bacteria of the coliform group in milk or water, used as an indicator of faecal contamination and poor plant hygiene.

The number of body cells, mainly white blood cells, present per millilitre of milk; a high count signals udder infection such as mastitis and poorer milk quality.

An inflammation of the udder tissue usually caused by bacterial infection, which raises somatic cell count, alters milk composition and reduces yield and shelf life.

Traces of veterinary drugs left in milk after treating a sick animal, which are illegal above set limits because they harm consumers and stop starter cultures from working.

The lowering of milk's freezing point below that of pure water due to dissolved lactose and salts; the value is used to detect added water in milk.

An instrument that measures the freezing point of a milk sample precisely, so that added water or adulteration can be detected from the freezing point depression.

The ratio of the mass of a milk sample to the mass of an equal volume of water, commonly measured with a lactometer and used with fat content to detect watering.

A calibrated floating hydrometer designed to read the specific gravity or density of milk at a stated temperature, helping to screen for added water.

A standard volumetric test in which sulphuric acid and amyl alcohol are added to milk in a Gerber butyrometer, then centrifuged, to read fat percentage directly.

A graduated glass tube with a bulb and stopper used in the Gerber fat test, in which separated fat collects in the neck for direct percentage reading.

The lipid portion of milk, mainly triglycerides, present as globules covered by a milk fat globule membrane; it carries flavour, vitamins and the value of butter and ghee.

A thin layer of phospholipids and proteins surrounding each fat globule in milk, which keeps globules apart and protects the fat from enzyme attack.

A process that forces milk under high pressure through a narrow valve, breaking fat globules into tiny ones so the cream does not separate and the texture becomes smoother.

The removal of fat-rich cream from whole milk, usually by a centrifugal separator, leaving skim milk behind; it is the first step in making cream, butter and ghee.

The mechanical agitation of ripened cream that causes fat globules to clump together and form butter grains, releasing buttermilk as a by-product.

A fat-rich dairy product made by churning cream, containing roughly 80 percent milk fat with water, salt and non-fat solids; it must be stored cold to prevent rancidity.

Clarified butter fat prepared by melting butter and boiling off moisture and curd, leaving a nearly pure fat with a long shelf life and characteristic cooked flavour.

A measure of the volatile fatty acids released from a fat sample under standard conditions, used to check the purity of ghee and detect adulteration with other fats.

A heat treatment that kills disease-causing bacteria in milk while causing minimal change in flavour; common forms are the holder method and the high temperature short time method.

Ultra high temperature treatment, heating milk briefly above 135 degrees Celsius and packing it aseptically so it keeps for months without refrigeration.

Filling sterile milk into pre-sterilised containers in a sterile environment, preventing recontamination and allowing long ambient storage of UHT products.

An enzyme test that confirms pasteurisation was effective, since alkaline phosphatase is destroyed by correct heating and its presence suggests underpasteurisation or raw milk contamination.

A selected preparation of live bacteria such as lactic acid bacteria added to milk to begin fermentation, control acidity and produce curd, yoghurt, cheese and cultured butter.

A group of bacteria that ferment lactose into lactic acid, lowering pH and preserving milk products; they are the main organisms in starter cultures and fermented milks.

A semi-solid product made by fermenting milk with lactic acid bacteria until casein coagulates; in Indian dairy practice it also means dahi, eaten plain or used to make lassi and chhana.

A soft coagulated product made by adding hot acid to hot milk and draining the whey; it is the base for rasgulla and sandesh and is a close relative of paneer.

An unripened cheese made by acid coagulation of hot milk, pressing the curd to remove whey; it is firm, sliceable and widely used in Indian cooking.

A preparation of the enzyme chymosin, traditionally from calf stomach, that coagulates milk casein in cheese making by cleaving kappa-casein and destabilising the micelles.

The main protein of milk, present as calcium phosphate stabilised micelles; it coagulates with acid or rennet and forms the structural base of cheese, paneer and casein products.

The pH at which a protein carries no net charge and is least soluble; for casein it is about 4.6, the point at which acid coagulation of milk is complete.

The force applied in the homogeniser valve, commonly around 150 to 200 bar, which determines how finely fat globules are broken and how stable the emulsion becomes.

Clean-in-place equipment that circulates cleaning and sanitising solutions through pipes, tanks and fillers without dismantling, using controlled flow, temperature and time.

The alkaline cleaning stage in dairy plants using sodium hydroxide solution at controlled temperature to remove fat and protein deposits from equipment surfaces.

The overall programme of cleaning and disinfecting plant, equipment and personnel to reduce microorganisms to safe levels and prevent contamination of processed milk products.

A drying method in which concentrated milk is atomised into hot air, evaporating water rapidly to produce fine milk powder particles with good solubility.

A dried dairy product made by removing nearly all water from milk, usually by evaporation followed by spray drying, giving a long shelf life and easy transport.

A preserved product made by evaporating part of the water from milk and adding sugar, which lowers water activity and stops microbial growth in the sealed can.

The removal of water from milk by boiling under vacuum at reduced temperature, concentrating solids before drying or condensing while limiting heat damage.

The increase in volume of ice cream caused by air incorporated during freezing, expressed as a percentage of the mix volume; it affects texture and cost.

The blended, pasteurised and homogenised mixture of milk, cream, sugar, stabiliser and emulsifier that is aged, frozen and whipped to make ice cream.