ICAR AICE-JRF/SRF Fermented Milks Technology: practice questions

1 · Classification of fermented milks worldwide · medium

Which fermented milk is classed as yeast-lactic?

1. Acidophilus milk
2. Kefir
3. Cultured buttermilk
4. Yoghurt

2 · Classification of fermented milks worldwide · medium

Under the Codex standard, what applies to a fermented milk that is heat-treated after fermentation?

1. It must be re-inoculated with live culture before it is sold
2. The requirement for viable starter organisms does not apply
3. It may no longer be described as a milk product of any kind
4. It must still contain at least 10^7 cfu/g of live starter

3 · Process steps and their effect on texture · hard

Mechanistically, why does heat-denatured beta-lactoglobulin improve yoghurt texture?

1. It binds kappa-casein, adding strands and water-binding sites to the gel
2. It hydrolyses kappa-casein so that the milk clots as in cheese making
3. It converts lactose to galactose, which raises viscosity in the gel
4. It chelates calcium so that colloidal calcium phosphate stays intact

4 · Process steps and their effect on texture · medium

Why are milk powders deaerated or given hydration time before yoghurt making?

1. Powder must ferment for some hours before inoculation
2. Air is needed for culture growth and must be added
3. Hydration time is needed to denature the whey proteins
4. Undissolved powder and air cause grainy texture

5 · Dahi, misti dahi, shrikhand and lassi · medium

Buffalo milk dahi is typically firmer than cow milk dahi because buffalo milk has:

1. Higher casein, fat and total solids
2. More lactose but much less protein overall
3. Lower casein and fat
4. No whey proteins at all

6 · Kefir, koumiss and yeast-lactic fermented milks · medium

Packaged kefir is reported to swell its packs during retail storage. The most likely cause is:

1. Mould growth on the inside of the lid
2. Coliform contamination from the plant's water supply
3. Continuing yeast activity producing carbon dioxide
4. Post-acidification by Lactobacillus bulgaricus

7 · Cultured buttermilk and sour cream · hard

Which organisms in a buttermilk culture convert citrate to diacetyl?

1. L. lactis biovar diacetylactis and Leuconostoc mesenteroides subsp. cremoris
2. Lactobacillus acidophilus and Bifidobacterium animalis subsp. lactis
3. Kluyveromyces marxianus and Saccharomyces cerevisiae
4. Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus

8 · Skyr, labneh and other concentrated fermented milks · medium

Which method concentrates fermented curd continuously by centrifugal force?

1. A nozzle separator of the quark type
2. A plate heat exchanger
3. A homogeniser run at very high pressure
4. A cloth bag hung overnight

9 · Probiotic fermented milks · hard

Why are cultures without L. bulgaricus (such as acidophilus–bifidus–thermophilus cultures) used for some probiotic yoghurts?

1. L. bulgaricus raises the pH and lets spoilage bacteria grow
2. L. bulgaricus is a pathogen and is banned from probiotic products
3. L. bulgaricus cannot grow in milk without added probiotics
4. L. bulgaricus post-acidification harms probiotic survival

10 · Fruit preparations and flavouring · medium

Why must fruit preparations for yoghurt be heat-treated and filled aseptically?

1. They get no further heat, so contaminants would spoil the yoghurt
2. Heat treatment converts fruit sugars into lactic acid before use
3. Heat treatment is needed to activate the yoghurt culture in the fruit
4. Aseptic filling is needed to keep the fruit pieces from sinking