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Maharashtra HSC Food Science and Technology study materials
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Maharashtra HSC Food Science and Technology practice questions

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Question 1Introduction to Food Science and Food Constituents

Which macronutrient is the primary source of energy in the typical Indian cereal-based diet and contributes about 70–80% of total energy intake?

  1. Dietary fibre
  2. Fat
  3. Carbohydrate Correct answer.
  4. Protein

Explanation

Cereals such as rice and wheat are rich in starch, and starch is a carbohydrate that the body hydrolyses to glucose for energy. In Indian diets, carbohydrate supplies roughly 70–80% of total calories. Protein and fat contribute much smaller shares, and fibre is largely non-energy-yielding.

Question 2Introduction to Food Science and Food Constituents

A food technologist wants to determine the moisture content of a biscuit sample. Which method is the standard reference procedure used in food analysis laboratories?

  1. Karl Fischer titration
  2. Kjeldahl digestion
  3. Soxhlet extraction
  4. Oven drying at 105 °C to constant weight Correct answer.

Explanation

Hot-air oven drying at about 105 °C removes free water until constant weight, giving the conventional moisture value for most solid foods. Karl Fischer titration is used for low-moisture or heat-sensitive samples. Soxhlet and Kjeldahl measure fat and nitrogen respectively, not moisture.

Question 3Introduction to Food Science and Food Constituents

Which protein fraction of wheat flour is chiefly responsible for forming the gluten network during dough mixing?

  1. Glutenin Correct answer.
  2. Prolamin (gliadin)
  3. Globulin
  4. Albumin

Explanation

Glutenin and gliadin together form gluten, but glutenin provides the elastic, extensible backbone of the network while gliadin contributes viscosity. Among the options given, glutenin is the fraction chiefly responsible for network formation. Albumins and globulins are soluble proteins that do not form gluten.

Question 4Introduction to Food Science and Food Constituents

During gelatinisation of rice starch, what happens to the starch granules when heated in excess water?

  1. They absorb water, swell irreversibly and lose their crystalline order Correct answer.
  2. They shrink and expel bound water
  3. They crystallise into a denser structure
  4. They dissolve completely into simple sugars

Explanation

On heating in water, starch granules take up water, swell and lose birefringence as hydrogen bonds break, and amylose leaches out. This irreversible swelling and loss of crystallinity is gelatinisation. Shrinking, crystallisation and conversion to sugars describe different processes.

Question 5Introduction to Food Science and Food Constituents

Which vitamin deficiency causes night blindness and is a public health concern in Maharashtra?

  1. Vitamin A Correct answer.
  2. Vitamin C
  3. Niacin
  4. Thiamine

Explanation

Vitamin A as retinal is required by rhodopsin in the rod cells of the retina, and deficiency impairs dim-light vision, producing night blindness. Thiamine, vitamin C and niacin deficiencies cause beriberi, scurvy and pellagra respectively, none of which present primarily as night blindness.

Question 6Introduction to Food Science and Food Constituents

Which mineral is essential for the formation of haemoglobin, and its deficiency is the most common nutritional anaemia in India?

  1. Iron Correct answer.
  2. Zinc
  3. Iodine
  4. Calcium

Explanation

Iron is the central atom of the haem group in haemoglobin, so inadequate intake or poor absorption leads to iron-deficiency anaemia. Calcium, zinc and iodine have other roles, such as bone mineralisation, enzyme function and thyroid hormone synthesis.

Question 7Introduction to Food Science and Food Constituents

Which functional property of egg white protein is exploited when it is whipped to form a stable foam in cakes and meringues?

  1. Foam formation Correct answer.
  2. Water binding
  3. Gelation
  4. Emulsification

Explanation

Whipping egg white unfolds ovalbumin and other proteins, which adsorb at the air-water interface and stabilise air cells, forming a foam. Emulsification stabilises oil-water mixtures, gelation sets a solid network on heating, and water binding holds moisture; none of these describes foam formation.

Question 8Introduction to Food Science and Food Constituents

A food sample is analysed by the Soxhlet method. Which constituent is being estimated?

  1. Total ash
  2. Crude fibre
  3. Crude protein
  4. Crude fat Correct answer.

Explanation

Soxhlet extraction uses a non-polar solvent such as petroleum ether to dissolve and extract lipids from the dried sample, giving the crude fat value. Protein is measured by Kjeldahl nitrogen, ash by incineration, and crude fibre by acid and alkali digestion.

Question 9Introduction to Food Science and Food Constituents

Which of the following is an example of a reducing sugar that can reduce Fehling's solution?

  1. Glucose Correct answer.
  2. Starch
  3. Cellulose
  4. Sucrose

Explanation

Glucose has a free aldehyde group that is oxidised while reducing cupric ions to cuprous oxide, so it gives a positive Fehling's test. Sucrose has no free reducing group, while starch and cellulose are polysaccharides that do not reduce Fehling's solution directly.

Question 10Introduction to Food Science and Food Constituents

Which pigment is responsible for the green colour of leafy vegetables, and its degradation during blanching is monitored in food processing?

  1. Chlorophyll Correct answer.
  2. Betalain
  3. Anthocyanin
  4. Carotene

Explanation

Chlorophyll a and b absorb red and blue light and reflect green, giving leaves their colour. During blanching, heat and acids can convert chlorophyll to pheophytin, which is dull olive-brown. Carotene is yellow-orange, anthocyanin is red-purple, and betalain is red-violet.

Question 11Introduction to Food Science and Food Constituents

Which type of fat is characterised by having all carbon atoms in the fatty acid chain joined by single bonds?

  1. Monounsaturated fat
  2. Trans fat
  3. Saturated fat Correct answer.
  4. Polyunsaturated fat

Explanation

Saturated fatty acids contain only single bonds between carbon atoms, so the chain is fully saturated with hydrogen and packs tightly, giving a higher melting point. Mono- and polyunsaturated fats contain one or more double bonds, and trans fats contain double bonds in the trans configuration.

Question 12Introduction to Food Science and Food Constituents

Why is fat added to the dough during preparation of biscuits rather than being omitted?

  1. Fat shortens gluten strands and gives a tender, crisp texture Correct answer.
  2. Fat prevents starch from gelatinising during baking
  3. Fat increases gluten strength and makes the dough tough
  4. Fat acts as a leavening agent producing carbon dioxide

Explanation

Fat coats flour particles and interferes with gluten development, so the gluten network is shortened and the product becomes tender and crisp. Fat is not a leavening agent and does not strengthen gluten; it also does not prevent starch gelatinisation, which proceeds during baking.

Question 13Introduction to Food Science and Food Constituents

Which of the following is a water-soluble vitamin that acts as a coenzyme in energy metabolism and is destroyed by prolonged high-temperature cooking?

  1. Vitamin K
  2. Thiamine Correct answer.
  3. Vitamin A
  4. Vitamin D

Explanation

Thiamine (vitamin B1) is water-soluble and is a coenzyme in carbohydrate metabolism. It leaches into cooking water and is degraded by heat, so it is easily lost during prolonged cooking. Vitamins A, D and K are fat-soluble and are not similarly leached.

Question 14Introduction to Food Science and Food Constituents

Which of the following is an example of a colloidal system present in milk, where fat globules are dispersed in an aqueous phase?

  1. Suspension
  2. True solution
  3. Emulsion Correct answer.
  4. Gel

Explanation

Milk fat is dispersed as tiny globules in the aqueous serum, which is an oil-in-water emulsion stabilised by the milk fat globule membrane. A true solution contains dissolved ions and molecules, a suspension has larger settling particles, and a gel is a structured semi-solid network.

Question 15Introduction to Food Science and Food Constituents

Which of the following is the correct order for the proximate analysis of a food sample?

  1. Moisture, crude fat, crude protein, crude fibre, ash, nitrogen-free extract Correct answer.
  2. Crude protein, moisture, ash, crude fat, crude fibre, nitrogen-free extract
  3. Moisture, ash, crude protein, crude fat, crude fibre, nitrogen-free extract
  4. Ash, moisture, crude fibre, crude protein, crude fat, nitrogen-free extract

Explanation

Proximate analysis conventionally begins with moisture, followed by fat, protein, fibre and ash, with nitrogen-free extract calculated by difference. Moisture is measured first because it affects the mass basis for all other determinations. The other sequences place ash or protein before moisture, which is not the conventional order.

Question 16Introduction to Food Science and Food Constituents

A food processor wants to reduce the Maillard browning in a dried milk powder. Which change in processing conditions would most effectively slow the reaction?

  1. Increase water activity to near 0.9
  2. Increase storage temperature
  3. Add more reducing sugar to the powder
  4. Lower storage temperature and keep water activity low Correct answer.

Explanation

The Maillard reaction between reducing sugars and amino groups is accelerated by heat and by water activities in the intermediate range. Lowering temperature and keeping water activity low slows both the reaction rate and molecular mobility. Raising temperature, raising water activity or adding reducing sugar would all increase browning.

Question 17Introduction to Food Science and Food Constituents

Which of the following is NOT a fat-soluble vitamin?

  1. Vitamin C Correct answer.
  2. Vitamin D
  3. Vitamin A
  4. Vitamin E

Explanation

Vitamin C is water-soluble and is not stored in body fat, so excess is excreted in urine. Vitamins A, D and E are fat-soluble and are absorbed with dietary lipids. The question asks for the exception, which is vitamin C.

Question 18Introduction to Food Science and Food Constituents

Which enzyme is used in the food industry to hydrolyse starch into glucose syrups?

  1. Lipase
  2. Protease
  3. Amylase Correct answer.
  4. Pectinase

Explanation

Amylases cleave the glycosidic bonds of starch, producing dextrins, maltose and glucose depending on the enzyme type and conditions. Lipases act on fats, proteases on proteins, and pectinases on pectin. Therefore amylase is the enzyme used for starch hydrolysis.

Question 19Introduction to Food Science and Food Constituents

Which of the following best explains why vitamin C is easily lost during the preparation of cut vegetables?

  1. It is water-soluble, heat-labile and sensitive to oxidation Correct answer.
  2. It is bound tightly to cellulose and cannot be absorbed
  3. It is converted to vitamin A during cooking
  4. It is fat-soluble and leaches into oil

Explanation

Vitamin C (ascorbic acid) dissolves in water, is destroyed by heat and is readily oxidised, especially when cut surfaces expose it to air and to ascorbate oxidase. Cutting, washing and prolonged cooking therefore cause substantial losses. It is not fat-soluble, not bound to cellulose, and not converted to vitamin A.

Question 20Introduction to Food Science and Food Constituents

Which of the following is a characteristic of dietary fibre that explains its role in lowering blood cholesterol?

  1. It is digested and absorbed in the small intestine
  2. Soluble fibre binds bile acids and increases their excretion Correct answer.
  3. It is completely hydrolysed by salivary amylase
  4. It provides a concentrated source of energy

Explanation

Soluble fibres such as beta-glucan and pectin trap bile acids in the gut and increase their faecal excretion. The liver then uses cholesterol to synthesise new bile acids, lowering blood cholesterol. Fibre is not digested or absorbed in the small intestine, is not an energy source, and is not hydrolysed by amylase.

Question 21Introduction to Food Science and Food Constituents

Which of the following statements about water activity (aw) is correct?

  1. Water activity measures the availability of water for microbial growth and chemical reactions Correct answer.
  2. Water activity is measured in units of grams of water per gram of food
  3. Water activity increases as food is dried below its monolayer value
  4. Water activity is the same as moisture content on a dry basis

Explanation

Water activity is the ratio of the vapour pressure of water in the food to that of pure water at the same temperature, and it reflects the fraction of water available for microorganisms and reactions. It is not identical to moisture content, does not increase on drying, and is dimensionless.

Question 22Introduction to Food Science and Food Constituents

In the context of food constituents, which of the following is a function of phospholipids such as lecithin in foods?

  1. Acting as a water-soluble vitamin
  2. Serving as the principal energy storage carbohydrate
  3. Providing the main structural protein of muscle
  4. Acting as an emulsifier at oil-water interfaces Correct answer.

Explanation

Phospholipids are amphiphilic molecules with a hydrophilic phosphate head and hydrophobic tails, so they orient at oil-water interfaces and stabilise emulsions. Lecithin from soy or egg is widely used as an emulsifier. They are not structural proteins, energy-storage carbohydrates or vitamins.

Question 23Introduction to Food Science and Food Constituents

Which of the following changes occurs during retrogradation of cooked rice on cooling?

  1. Fat crystallises and forms a white bloom
  2. Starch granules absorb more water and swell further
  3. Amylose chains reassociate and the rice becomes firm and less digestible Correct answer.
  4. Proteins denature and form a rigid gel

Explanation

On cooling, amylose chains in gelatinised starch reassociate through hydrogen bonding into ordered crystalline regions, making the product firm and harder to digest. This is retrogradation, which is distinct from further swelling, protein gelation and fat bloom.

Question 24Introduction to Food Science and Food Constituents

Which of the following is an example of an intrinsic factor that affects the bioavailability of a mineral from a meal?

  1. Presence of phytate in whole cereals Correct answer.
  2. Colour of the serving plate
  3. Amount of water consumed with the meal
  4. Time of day the meal is eaten

Explanation

Phytate in whole cereals and legumes chelates minerals such as iron, zinc and calcium, reducing their absorption and hence their bioavailability. Water intake, meal timing and plate colour do not chemically interfere with mineral absorption.

Question 25Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

In food systems, 'bound water' is best described as water that is

  1. the water removed first during hot-air drying of a food
  2. the water that forms the continuous phase of an emulsion
  3. held tightly by hydrogen bonding to macromolecules and does not freeze readily Correct answer.
  4. free in capillaries and easily expressed by pressing the tissue

Explanation

Bound water is associated closely with hydrophilic groups of proteins and polysaccharides through hydrogen bonding, so it has reduced mobility and does not freeze at the usual freezing point. It is not available as a solvent for solutes to the same extent as bulk water. This distinction matters for microbial stability and for drying behaviour.

Question 26Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Water activity (a_w) of a food is defined as

  1. the ratio of the vapour pressure of water in the food to that of pure water at the same temperature Correct answer.
  2. the freezing point depression of the food divided by that of pure water
  3. the total moisture content expressed as a percentage of dry matter
  4. the mass of water per unit mass of the food multiplied by 100

Explanation

Water activity is the equilibrium ratio of the water vapour pressure above the food to that of pure water at the same temperature, and it is numerically close to the relative humidity of the surrounding air at equilibrium. It reflects how much water is available for microbial growth and chemical reactions, not how much water is present. Moisture content alone does not predict stability.

Question 27Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Most spoilage bacteria stop multiplying when water activity falls below approximately

  1. 0.60
  2. 0.99
  3. 0.75
  4. 0.91 Correct answer.

Explanation

Most spoilage bacteria require a water activity above about 0.91, and this is why foods must be dried or salted well below that level for bacterial stability. Yeasts and moulds tolerate lower values, with xerophilic moulds growing near 0.65. The 0.60 value is the general lower limit for any microbial growth.

Question 28Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Which change occurs when a starch dispersion is cooled after gelatinisation?

  1. Amylose chains reassociate into ordered regions, causing retrogradation and syneresis Correct answer.
  2. Amylopectin is hydrolysed to maltose by residual acid
  3. Starch granules absorb water and swell irreversibly for the first time
  4. The gelatinised starch converts entirely to resistant starch within minutes

Explanation

On cooling, linear amylose molecules reassociate through hydrogen bonding into ordered crystalline regions, a process called retrogradation that can expel water as syneresis. Amylopectin retrogrades much more slowly because its branched structure hinders alignment. Retrogradation is responsible for staling of cooked rice and bread.

Question 29Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

A food technologist wants to thicken a sauce without sweetness and without gelling on cooling. The most suitable hydrocolloid is

  1. modified waxy maize starch Correct answer.
  2. sucrose
  3. gelatin at refrigerated temperature
  4. high-methoxyl pectin with added calcium

Explanation

Modified waxy maize starch is based on amylopectin, which gives viscosity and resistance to retrogradation without sweetness and without forming a firm gel on cooling. Sucrose would add sweetness, and high-methoxyl pectin plus calcium sets a gel. The choice balances the functional requirement of thickening with stability.

Question 30Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

In the Maillard reaction, the initial condensation occurs between

  1. two amino acids joined by a peptide bond
  2. a fat-soluble vitamin and a peroxide radical
  3. a carboxyl group of a fatty acid and a hydroxyl group of glycerol
  4. a carbonyl group of a reducing sugar and an amino group of an amino acid or protein Correct answer.

Explanation

The Maillard reaction begins when the carbonyl group of a reducing sugar condenses with the free amino group of an amino acid, peptide or protein to form a glycosylamine, which rearranges and later produces brown pigments and aroma compounds. Non-reducing sugars such as sucrose do not react unless hydrolysed first. The reaction is favoured by heat and intermediate water activity.

Question 31Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Which sugar is a non-reducing disaccharide?

  1. Lactose
  2. Sucrose Correct answer.
  3. Maltose
  4. Cellobiose

Explanation

Sucrose is formed from glucose and fructose linked through both anomeric carbons, so it has no free reducing group. Lactose, maltose and cellobiose all retain a free anomeric carbon on the glucose unit and therefore reduce alkaline copper solutions. This property explains why sucrose does not brown by the Maillard route until it is hydrolysed.

Question 32Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

A sample of honey is tested and gives a positive Benedict's test. The most likely reason is the presence of

  1. starch
  2. glucose and fructose Correct answer.
  3. cellulose
  4. sucrose only

Explanation

Benedict's test detects reducing sugars, and honey contains substantial free glucose and fructose, both of which reduce copper(II) to red copper(I) oxide. Sucrose is non-reducing and would not respond, and starch and cellulose are polysaccharides that are not detected by this test. The result therefore confirms the presence of reducing monosaccharides.

Question 33Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Essential amino acids are those that

  1. cannot be synthesised by the human body in adequate amounts and must come from the diet Correct answer.
  2. contain sulphur in their side chains
  3. are synthesised in the body from other amino acids and are never limiting
  4. are only found in animal proteins

Explanation

Essential amino acids cannot be made by the human body at a rate sufficient to meet needs and must be supplied by food. Their presence in adequate proportions determines protein quality, which is why cereals and pulses are often combined. Sulphur content and animal origin are unrelated to the essential classification.

Question 34Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

The isoelectric point of a food protein is the pH at which

  1. the net electrical charge on the protein is zero and solubility is minimal Correct answer.
  2. peptide bonds are hydrolysed most rapidly
  3. the protein carries the maximum net negative charge
  4. the protein is fully denatured and coagulated

Explanation

At the isoelectric point the positive and negative charges on the protein balance, giving zero net charge, so electrostatic repulsion between molecules is minimised and they aggregate and precipitate. This principle is used in isoelectric precipitation of casein at about pH 4.6. Solubility is lowest, not highest, at this pH.

Question 35Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Casein is precipitated from milk for cheese making by acidification to approximately

  1. pH 8.2
  2. pH 2.0
  3. pH 6.7
  4. pH 4.6 Correct answer.

Explanation

Casein has an isoelectric point near pH 4.6, so acidification of milk to that pH causes the micelles to lose their stabilising charge and aggregate into a curd. Fresh milk is near pH 6.7, well above this point, which is why it must be acidified. Lactic acid bacteria or added acid accomplish the shift.

Question 36Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

During heating of milk, the whey protein that denatures and binds with kappa-casein, affecting rennet coagulation, is mainly

  1. alpha-casein
  2. proteose peptone
  3. bovine serum albumin
  4. beta-lactoglobulin Correct answer.

Explanation

Beta-lactoglobulin is the major whey protein and is heat-labile; on heating it unfolds and interacts through disulphide bonds with kappa-casein on the micelle surface. This interaction hinders rennet action and reduces curd firmness in heated milk. Alpha-casein is a micellar protein and is not the principal heat-reactive whey fraction.

Question 37Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Which statement correctly distinguishes fats from oils at room temperature?

  1. Fats are solid and contain a higher proportion of saturated fatty acids, while oils are liquid and richer in unsaturated acids Correct answer.
  2. Oils are always of plant origin and fats always of animal origin
  3. Fats have lower melting points than oils of the same chain length
  4. Fats contain glycerol while oils contain no glycerol backbone

Explanation

Fats are solid at room temperature because their higher saturated fatty acid content allows tighter packing and higher melting points. Oils are liquid because unsaturated fatty acids introduce kinks that prevent close packing. Both fats and oils are triglycerides, so the glycerol backbone is common to both.

Question 38Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

The iodine value of a fat is a measure of

  1. the free fatty acid content released by lipolysis
  2. the melting point of the fat
  3. the degree of unsaturation of its fatty acids Correct answer.
  4. the amount of moisture present in the fat

Explanation

The iodine value expresses the grams of iodine absorbed by 100 g of fat, which reflects the number of double bonds and hence the degree of unsaturation. A high iodine value indicates a highly unsaturated, usually liquid oil. Free fatty acid content and moisture are measured by separate titrimetric and gravimetric methods.

Question 39Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Hydrolytic rancidity in butter on prolonged storage is caused by

  1. cleavage of ester bonds releasing free short-chain fatty acids such as butyric acid Correct answer.
  2. polymerisation of triglycerides into cyclic compounds
  3. loss of water from the fat crystals
  4. oxidation of double bonds forming hydroperoxides

Explanation

Hydrolytic rancidity results from lipase activity or chemical hydrolysis of the ester bonds in triglycerides, releasing free fatty acids. In butter, short-chain acids such as butyric acid are liberated and give a characteristic rancid odour even in small amounts. Oxidative rancidity is a separate mechanism involving double bonds.

Question 40Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

An antioxidant such as BHA added to an edible oil functions mainly by

  1. absorbing moisture that would otherwise hydrolyse triglycerides
  2. raising the melting point of the oil to improve stability
  3. binding free fatty acids released by lipase
  4. donating hydrogen to lipid radicals and interrupting the chain propagation of autoxidation Correct answer.

Explanation

Primary antioxidants such as BHA and BHT donate a hydrogen atom to lipid peroxyl or alkyl radicals, forming a stable radical that cannot propagate the autoxidation chain. This delays the formation of hydroperoxides and the onset of oxidative rancidity. They do not act on moisture or on hydrolytic rancidity.

Question 41Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Trans fatty acids in partially hydrogenated vegetable oil are formed because hydrogenation

  1. oxidises the oil to hydroperoxides
  2. converts some cis double bonds to the more stable trans configuration Correct answer.
  3. hydrolyses the triglyceride into glycerol and fatty acids
  4. removes all double bonds to give fully saturated chains

Explanation

Partial hydrogenation saturates some double bonds and, as an intermediate, allows remaining cis double bonds to isomerise to the thermodynamically more stable trans form. Trans fats raise LDL cholesterol and are therefore restricted in many countries. Complete hydrogenation would give a fully saturated, hard fat with no double bonds.

Question 42Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Which vitamin deficiency is classically associated with night blindness and xerophthalmia?

  1. Vitamin A Correct answer.
  2. Thiamine
  3. Vitamin D
  4. Vitamin K

Explanation

Vitamin A as retinal is required for the visual pigment rhodopsin, so deficiency impairs dark adaptation and causes night blindness. Continued deficiency leads to xerophthalmia and keratomalacia. Vitamin D, vitamin K and thiamine deficiencies cause rickets, bleeding disorders and beriberi respectively.

Question 43Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Vitamin C is easily destroyed during cooking of vegetables mainly because it is

  1. converted to a provitamin by heat
  2. water-soluble, heat-labile and readily oxidised Correct answer.
  3. insensitive to light and oxygen
  4. fat-soluble and stable to boiling

Explanation

Ascorbic acid is water-soluble, so it leaches into cooking water, and it is readily oxidised to dehydroascorbic acid and further to inactive products, a process accelerated by heat, light, oxygen and copper ions. This is why minimal water and short cooking times preserve it. Its water solubility and oxidisability together explain the losses.

Question 44Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

The mineral that is a central component of the haem group in haemoglobin and myoglobin is

  1. iron Correct answer.
  2. zinc
  3. calcium
  4. iodine

Explanation

Iron sits at the centre of the porphyrin ring in haem, where it binds oxygen reversibly for transport and storage. Haem iron from animal foods is absorbed more efficiently than non-haem iron from plants. Calcium, zinc and iodine serve other roles such as bone structure, enzyme catalysis and thyroid hormone synthesis.

Question 45Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Phytate in whole cereals and legumes reduces the bioavailability of minerals mainly by

  1. competing with minerals for absorption carriers
  2. raising gastric pH to alkaline levels
  3. chelating divalent cations such as iron and zinc into insoluble complexes Correct answer.
  4. oxidising ferrous iron to ferric iron

Explanation

Phytic acid carries multiple phosphate groups that chelate divalent cations, especially iron, zinc and calcium, forming insoluble complexes that resist absorption in the intestine. Processing methods such as fermentation, soaking and germination reduce phytate and improve mineral availability. Simple competition for carriers does not describe the main mechanism.

Question 46Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Which amino acid is typically limiting in cereal proteins such as wheat and rice?

  1. Methionine
  2. Leucine
  3. Glutamic acid
  4. Lysine Correct answer.

Explanation

Cereal storage proteins are rich in glutamine and proline but low in lysine, so lysine is the first limiting amino acid for cereals. Pulses, in contrast, are low in methionine but supply lysine, which is why cereal-pulse combinations improve protein quality. Glutamic acid is abundant rather than limiting in cereals.

Question 47Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

The biological value of a protein is highest when the protein

  1. supplies essential amino acids in proportions closely matching body requirements Correct answer.
  2. has the largest molecular weight among available proteins
  3. is consumed together with a large amount of fat
  4. contains the greatest total quantity of non-essential amino acids

Explanation

Biological value measures the proportion of absorbed protein nitrogen retained by the body, and it is highest when the essential amino acid pattern matches requirements closely, as in egg and milk proteins. Molecular size and the amount of non-essential amino acids do not determine retention. Fat intake does not raise protein quality.

Question 48Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

Gelatin sets to a gel on cooling because its structure is

  1. a polysaccharide cross-linked by calcium ions
  2. a partially hydrolysed collagen in which triple-helical junction zones re-form Correct answer.
  3. a globular protein that coagulates irreversibly by heat
  4. a mixture of free amino acids that crystallises

Explanation

Gelatin is obtained by partial hydrolysis of collagen, giving chains that on cooling re-form triple-helical junction zones, trapping water in a thermoreversible gel that melts again on heating. Globular proteins coagulate irreversibly, which is a different behaviour. Gelatin is a protein, not a polysaccharide.

Question 49Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

During storage of a dried food at a water activity of 0.4, lipid oxidation often proceeds faster than at 0.7 because

  1. at 0.4 the food contains no oxygen at all
  2. at 0.7 the fat becomes fully saturated
  3. at 0.4 antioxidants are activated by dryness
  4. at very low a_w, water no longer shields catalytic metal ions and hydroperoxide decomposition is favoured Correct answer.

Explanation

In the low-to-intermediate moisture region, a small amount of water hydrates metal ions and quenches radicals, so removing it increases catalytic oxidation and hydroperoxide breakdown. As a_w rises towards 0.7, this protective hydration increases and oxidation slows, although at still higher values microbial and other reactions dominate. The effect is a well-known feature of moisture sorption isotherms for oxidation.

Question 50Food Chemistry: Water, Carbohydrates, Proteins, Lipids, Vitamins and Minerals

In a food, 'bound water' is best described as water that

  1. is the portion of total water that can be removed by simple draining of the product
  2. is held by hydrogen bonding to macromolecules and other solutes and shows reduced mobility and lowered vapour pressure Correct answer.
  3. is chemically bonded into the structure of carbohydrates and proteins and is unavailable as a solvent
  4. is water added during processing that has not yet equilibrated with the food matrix

Explanation

Bound water is the fraction of moisture associated through hydrogen bonding with proteins, polysaccharides and solutes, so it has restricted mobility, does not freeze readily and exerts a lower vapour pressure than bulk water. It is not a fixed chemical component of the molecule, and it is not simply free water awaiting equilibration. This reduced mobility is why bound water is largely unavailable for microbial growth and chemical reactions.