UPMSP Vocational Dairy Technology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Average total solids of cow milk

About 12–13% total solids, comprising fat, protein, lactose and ash; buffalo milk is higher at 16–17% because of its greater fat and protein content.

Isoelectric point of casein

pH 4.6, the point at which casein carries no net charge and coagulates; this is the basis of acid coagulation in paneer and chhana manufacture.

Clot-on-boiling test

A platform test in which a milk sample is boiled in a tube; visible coagulation indicates acidity above about 0.20% and the milk is rejected at reception.

Methylene blue reduction test

A bacteriological grading test in which methylene blue decolourises faster with higher bacterial load; reduction in under 2 hours indicates poor quality milk.

Psychrotrophic bacteria in stored milk

Cold-tolerant organisms such as Pseudomonas that grow at refrigeration temperature and produce heat-stable proteases and lipases causing spoilage after pasteurisation or UHT.

HTST pasteurisation conditions

Heating milk to 72 °C for 15 seconds followed by rapid cooling; it inactivates alkaline phosphatase, which is the standard indicator of adequate pasteurisation.

Homogenisation pressure and effect

Forcing milk through a valve at 150–250 bar reduces fat globules below 2 micrometres, preventing cream separation and producing a stable emulsion.

Butter legal composition

Butter must contain at least 80% milk fat, no more than 16% moisture and no more than 2% salt; these limits define its standard of identity.

Ghee fat specification

Clarified butter fat must contain at least 99.7% fat and no more than 0.3% moisture; the Reichert-Meissl value is used to confirm purity.

Yoghurt starter organisms

Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, used together at 42–45 °C to ferment milk to pH 4.6 and produce yoghurt.

Paneer manufacture

Hot milk at 85–90 °C is coagulated with citric acid or vinegar, the curd is pressed in a hoop and chilled in water to give a firm product.

Spray drying temperatures

Inlet air at about 180–200 °C and outlet air at 80–90 °C dry atomised milk concentrate to a powder with no more than 4% moisture.

Sweetened condensed milk preservation

Added sucrose at about 15–16% raises osmotic pressure sufficiently to inhibit microbial growth, so the product needs no sterilisation after canning.

Ice cream overrun

The percentage of air incorporated during freezing, calculated as (mix volume minus ice cream volume) divided by ice cream volume times 100; typical values are 50–100%.

Ice cream ageing

Holding the pasteurised and homogenised mix at 4 °C for 2–24 hours so fat crystallises and stabilisers hydrate, improving overrun and texture.

Rennet action on casein

Chymosin cleaves kappa-casein at the Phe105-Met106 bond, destabilising the casein micelle and causing coagulation in cheese manufacture.

Cheddar cheese moisture

Cheddar typically contains 35–36% moisture and about 30% fat; the moisture-in-fat-free-substance value determines its cheese classification.

Somatic cell count significance

A count above about 400,000 cells per mL indicates mastitis; bulk tank limits are typically 500,000 cells per mL and higher counts reduce cheese yield.

Coliform standard in pasteurised milk

Fewer than 10 colony-forming units per mL; higher counts indicate post-pasteurisation contamination from equipment, hands or water.

Bacteriophage in starters

Viruses that infect starter bacteria and cause slow or failed acid production; controlled by strain rotation, sanitised air and rigorous plant cleaning.

DVS starter cultures

Direct vat set freeze-dried cultures added straight to the vat without propagation, reducing contamination and phage risk in fermented milk production.

CIP alkaline wash

A 1–2% sodium hydroxide solution at 70–80 °C circulated to remove milk fat and protein soil from tanks, pipes and pasteurisers during cleaning.

CIP acid wash

A 0.5–1% nitric acid solution circulated after the alkaline wash to dissolve mineral scale and milk stone deposits on dairy equipment surfaces.

Reichert-Meissl value

Millilitres of 0.1 N alkali needed to neutralise volatile fatty acids from 5 g of fat; it is about 28–30 for pure ghee and falls with vegetable fat adulteration.

Maillard reaction in milk

Reaction between lactose and lysine during heating that causes browning and loss of available lysine, especially in UHT milk and dried milk powders.

Gerber fat test formula

Fat percentage equals the butyrometer reading multiplied by 18 and divided by the sample weight; 11.33 g of milk is used with sulphuric acid and amyl alcohol.

Kjeldahl protein factor

Total nitrogen multiplied by 6.38 gives milk protein percentage, because milk protein contains about 15.67% nitrogen on average.

Cryoscopic test for added water

Normal milk freezes at about −0.54 °C; added water raises the freezing point by roughly 0.0054 °C per 1% water, so the shift quantifies adulteration.

Titratable acidity of fresh milk

Fresh milk titrates at 0.14–0.16% lactic acid with 0.1 N sodium hydroxide and phenolphthalein; higher values indicate developed acidity or mastitis.

Filtration versus clarification

Filtration removes visible dirt and cells by passing milk through a filter; clarification uses centrifugal force to remove fine sediment without separating cream.

Hardening of ice cream

Bringing the frozen product from about −6 °C to −18 °C or below in a hardening tunnel or room to set the remaining water as ice and stabilise texture.

Acid versus rennet casein

Acid casein is precipitated by acid at pH 4.6, while rennet casein is coagulated by chymosin; both are washed to remove lactose and then dried.