DAIRY CHEMISTRY

 

Chemistry of Dairy Products

Compiled by: - Mr. Abhay Pandey

 

Q. What is Auto oxidation?

A. The oxidation of fat or an oil at relatively low temperature such as 100 degree c

 

Q. What is thermal polymerization?

A. The changes taking place in oil and fat at 200-300 degree c in the absence of air.

 

Q. What is thermal oxidation?

A. Oxidation of fat and oil at about 200 degree c in the presence of oxygen.

 

Q. How many phases are there in Auto oxidation?

A. 3- initiation, propagation and termination

 

Q. On auto oxidation oxygen attacks on?

A. Unsaturated bonds

 

Q. Which type of milk is more prone to Auto oxidation (Cow milk or Buffalo Milk?)

A. Buffalo milk(rate of auto oxidation of Buffalo milk is double that of cow milk

 

Q. Refractive index of oil increases during thermal oxidation caused by?

A. Accumulation of conjugated fatty acid.

 

Q. Di electric coefficient of oil decreases during thermal oxidation which is caused by?

A. Polar oxidized components.

 

Q. Conductivity of oil during thermal oxidation increases because of

A. Polar component.

 

Q. Iodine value of oil decreases during thermal oxidation because of?

A. Formation of oxidized fat products.

 

Q. Which human body part contains thiokinase and succinyl dehydogenase enzymes?

A. Liver.

 

Q. Which types of double bond is more prone to Auto oxidation?

A. Non conjugated double bond.

 

Q. Relative rate of oxidation for arachidonic, linolenic, linoleic and oleic acids are in the ratio of ............., respectively.

A. 40:20:10:1

 

Q Between Cis and Trans isomers which is more prone to auto oxidation?

A. Cis

 

Q................ Of the fatty acid distribution of a natural fat reduces the rate of oxidation

A. Randomization

 

Q. Rate of oxidation......... with increase in the temperature.

A. Increases

 

 

Q. Rate of oxidation............ in direct proportion to the           surface area of the lipid exposed to air. 

A. Increases

 

Q.  At  water activity of  about.... , oxidation proceeds very rapidly.

A. 0.1

 

Q.Increasing the water activity to about........ retards lipid oxidation and often produces a minimum rate.

A. 0.3

 

Q.AEF =?

A. AEF= Induction period of treated sample (It)/Induction period of blank (Ib)

    *where, AEF is Antioxidant efficiency factor

 

Q. PF=?

A. PF=(It-Ib) /Ib

     *where PF is Protection factor

 

Q. Which bacteria causes late blowing defect?

A. Clostridium tyrobutyricum

 

Q. Early blowing defect is caused by…….. in SCM?

A. E. Coli

 

Q. Calcium sensitive casein?

A. Alpha s1, alpha s2 and Bita casein

 

Q. Rennet acts on which part of casein?

A. K-casein

 

Q. Rennet enzyme coagulates casein in.....  Steps

A. 2

 

Q.Rennet breaks K-casein in 2 parts named-

A. Para K-casein and glycomarcro peptides

 

Q. Between para K-casein and GMP which has carbohydrates?

A. GMP

 

Q. Between para K- casein and GMP which is the hydrophilic part of K casein

A. GMP

 

Q. How much part of casein is represented by K-casein?

A. 12-15%

 

Q. Rennet enzyme hydroxylases which bond of K-casein?

A. Phe105-met106

 

 

Q. GMP represents how much part of the K-casein?

A. Aprrox 30%

 

Q.GMP represents how much part of the casein

A. 3-5%

 

Q. After the removal of GMP from the surface of casein, zeta potential reduces

A. From - 20mV to-10mV

 

Q. Which mineral is essential for rennet coagulation?

A. Calcium

 

Q. Carbohydrates residue president in GMP?

A. N-acetyl neuramic acid

 

Q. If NaCl is added to the milk, RCT will?

A. Increase

 

Q. Rennet enzyme belongs to which group of enzymes?

A. Aspartic acid proteinase(EC.3.4.23)

 

Q. Molecular mass of calf chymosin?

A. 35,600Da

 

Q. How many amino acids are there in calf chymosin?

A. 323

 

Q. The optimum temperature of milk coagulation by chymosin at pH 6.6 is?

A. 45 degree C

 

Q. The Q10 of enzymatic phase of rennet coagulation is

A. 2

 

Q.  Q10 of second phase of rennet coagulation is

A. 11-16

 

Q Secondary phase of rennet coagulation does not occur below....... Temperature

A. 15 degree C

 

Q. Optimum coagulation temperature for milk coagulation by rennet action

A. 30-32 degree C

 

Q. How much temperature is required for rennet inactivation?

A. More than 55 degree C

 

Q. If milk is heated to 70 degree C than RCT will?

A. Increase ( due to interaction between K-casein and bita lactoglobulin)

 

Q. Which equation describes inverse relation between RCT and enzyme concentration

A. Holter equation

 

Q. Which stage of Rennet coagulation is most affected by pH of milk?

A. Primary stage

 

Q. As pH decreases RCT will?

A. Reduce

 

Q. Addition of calcium less than 50m mol/l will.......... RCT

A. Reduce

 

Q. Addtion of calcium in the milk will.......... The rate of firmimg gel?

A. Increase

 

Q. How many cystine residues are present in K-casein?

A. 2

 

Q.How many cystine residues are present in bita lactoglobulin?

A. 5

 

Q.  As the casein conc. increases, the rate of aggregation........

A. Increases

 

Q. Formograph is used for?

A. Measurement of RCT

 

Q. Which order of kinetics is followed by syneresis in cheese making?

A. First order kinetics

 

Q. If moisture content of cheese is high, ripening will be?

A. Faster

 

Q. Lower the pH,......... Will  syneresis

A. Higher

 

Q. If cooking temperature is high, syneresis will?

A. High

 

Q.If salt is added to the cheese,  syneresis will

A. Increase

 

Q. Salt is added to various varieties of cheese @

A. Approx  2%salt in moisture

 

Q. Of 1kg salt is added to the cheese how much water will expelled out?

A. 2kg

 

Q Which bacteria is essential for blue veined cheese?

A. Propionic bacteria

 

Q What %of total milk production of india is used for khoa making?

A.7%

 

Q. The higher emulsifying capacity of buffalo milk is due to

A. The presence of higher proportions of butyric acid containing triglycerides 50%

 

Q. Three types of khoa

A. Pindi, dhap, danedar

 

Q. Type of khoa which made from higher acidic milk?

A .Danedar

 

Q. Homogenised milk produces …...... body in khoa than unhomogenised milk

A. Softer

 

Q. On khoa making pH of milk

A. Decreases

 

Q. Cooked flavour in khoa comes from

A. Generation of sulphydryl compound by denaturation of bita lactoglobulin

 

Q. On khoa making soluble calcium content of milk

A. Decreases

 

Q. On khoa making, lactose solution will become......

A. Super saturated

 

Q. The colour of the khoa becomes brown because of the …......... reaction

A. Maillard

 

Q. On khoa making iron content will.......if it is made in iron kadhayi

A. Increase upto 100ppm

 

Q. Shelf life of khoa?

A.5days at room temperaure

 

Q. Preservatives used for khoa preservation

A. Potassium sorbate and potassium metabisulphite

 

Q. Irradiation of khoa extend the shelf life of khoa from... to....

A.5 to 25

 

Q .If storage temperature of khoa is high ,evaporation of water will be

A .High

 

Q. Acidity of khoa …...... with storage

A. Increases

 

Q. Peroxide value of khoa …....with storage

A. Increases

 

Q. Free fatty acid content of khoa …...with storage

A. Increases

 

Q. Tyrosine value of khoa ….... with storage

A. Increases

 

Q. Main resposible micro organism for spoilage of khoa

A. Aerobic spore former and moulds

 

Q. If khoa is stored excessively long period at 5-10 degree C which defect will appear

A. Stale

 

Q. Formation of gel or a voluminous sediment or creamy layer during storage of evaporated milk, defect is called

A. Age gelation

 

Q. The more intense sterilization and the less conc of product, more …... gelation will proceed

A. Slowly

 

Q. The main cause of age gelation is ?

A. Physio chemical change in casein

 

Q. Microorganism responsible for age gelation

A.Bacillus cereus

 

Q .Part of whey protein responsible for age gelation

A. Bita lactoglobulin

 

Q. Part of casein which is mainly responsible for age gelation

A.K-casein

 

Q. Beta lactoglobulin unfold and lose its globular structure above ….... (Temperature)

A.55 degree C

 

Q. Gelation time of UHT milk ….......with severity of heating during pre-heating and sterilization

A. Increased

 

Q. Milk treated by indirect UHT process is …....... stable than milk treated by UHT processes

A. More stable

 

Q. If storage temperature of UHT conc milk increases, gelation time …....

A. Decrease

 

Q. Gelation time is …....... related to SNF content

A. Inversely

 

Q .Additive which increases the shelf life of UHT milk by 6 months

A .Long chain polyphosphate

 

 

Q. How sodium hexametaphosphate retards gelation

A. It chelates the calcium

 

Q. SCM has long shelf life because of ?

A. High concentration of sugar

 

Q. Sugar concentration in the water in SCM

A. 62.5-64.5%

 

Q. Ability of milk to withstand high temperature treatment without any visible gelation

A. Heat stability

 

Q. What is HCT

A. Heat coagulation time is defined as the time that elapses between placing a sample of milk in an oil bath and the onset of visible coagulation

 

Q. Type A milk gives at what pH maxima in HCT pH graph

A. 6.7

 

Q. In HCT pH graph, on what pH type A milk shows minimum HCT?

A. 6.9

 

Q. Calcium ion ….....HCT throughout the pH range 6.4-7.4

A.Reduce

 

Q. Calcium chelators (citrate and phosphate)......... stability

A .Increases

 

Q. Addition of k casein to milk …........stability in the pH range of the HCT minimum, but not at pH values more than the maximum

A .Increases

 

Q. Reducing the level of colloidal calcium phosphate …..... Stability in the region of the HCT maximum

A. Increases

References :-

1. NDRI class notes by Dr. Kamal Gandhi

2. Previous year question papers