Food Science

Rancidity: The chemical deterioration of the fats caused by the uptake of oxygen or water (hydrolysis). The development of off-flavour due to oxidation of fats is called rancidity. The unpleasant taste and odour is due to the formation of peroxides.

Antioxidant: Any substance that reduces oxidative damage by scavenging free radicals/electrons. Antioxidant is a substance which prevents oxidation of foods caused by oxygen, thus prolongs their shelf-life, wholesomeness & palatability. or Any micronutrient that neutralizes the action of free radicals. A number of phenols (Hydroquinone, pyrogallal) and naturally occurring substances like ascorbic acid, glutathione, tocopherol (Vit E) are used as antioxidants. In the production of dehydrated potato product, BHT (Butylated Hydroxy Toluene), BHA (Butylated hydroxyl anisole), propyl gallate are used as antioxidents and KMS (Potassium metabisulphite) is used as antioxidant in preserving fruit juices.

Blanching: Heats treatment of vegetable in boiling water or steam for 2-5 mint to inactivate enzymes and to destroy peroxides. It is also known as scalding, par boiling or pre-cooking. The blanching operation usually takes place at 85 to 90 ^oC but below 100^oC. The produce after blanching is cooled immediately.

Blanching indicator: Peroxidase and catalase enzymes are used as indicator of sufficient blanching. These are most heat resist enzyme of plant origin.

Brining: The process of preservation of vegetables in a salt solution of suitable concentration for certain period of time is called brining.  Hot brine of 1-3% concentration is used for covering vegetables and is filled at 79 – 82^oC, leaving a head space of 0.3 – 0.5 cm.

Brix: A measure of the total soluble solids in fruit/ vegetable juice, calibrated in terms of pure sucrose i.e. 1⁰Brix = 1% sucrose measured with a refractometer.

CIPC: CIPC also called chloropropham is applied as thermal fog. CIPC is a sprout suppressant in potatoes.

Critical Control point: Any step at which biological, chemical or physical factors can be controlled.

Curing: A post harvest treatment of tuber and bulb crops by exposing them to relatively high temperature and high humidity to facilitate the drying of upper skin and suberization of the outer tissue, periderm formation and healing of injured surface reduces the moisture loss through transpiration, prevent microbial attack, and reduce rotting and results more shelf life.

CUT-OUT: Examination of canned product to determine their quality, whose measurements are made of their weight of drained solids and the weight, density and TSS of the syrup or covering liquid i.e. brine is called Cut Out. The syrup / brine which is added to the product will be diluted by the water content present in the potato or other commodity and will generally cut out from original brine strength of 2% to 1%.

Dehydration: A drying process where moisture of food is removed by artificially produced heat under controlled conditions of temperature, relative humidity (RH) and air flow. Synonymous of dehydration is desiccation. Loss of water from the body due to loose motions is also called dehydration.

Double seaming machine: It is a machine used for sealing of the cans. This operation is done after can flanging. It is also called double can seamer (Plate 5).

Embossing: It is used in can end covers. It is process of giving impression of prints on covers. It is the process to raise the surface of into bosses. It is the coding of can’s end with the coding machine.

Enzymatic browning: Potatoes have a tendency to turn brown when damaged or when cut, surfaces are exposed to air and this is due to enzymatic reactions. The formation of brown colour is due to the action of the enzyme phenol (also known as polyphenol oxidase, tyrosinase or catechoase) on phenolic substances. Normally, the phenolic substrates are separate from phenolase in the intact tissues and browning does not occur. When foods containing such substances are cut and exposed to air rapid browning of the cut surface takes place. Polyphenols (in cells) + oxygen in cells cause browning after cutting or bruising only.

Equilibrium relative humidity (ERH): It is defined as neither percentage of relative humidity at which the moisture content of the sample is in equilibrium and results neither loss nor gain of the moisture content by the sample. In ERH, the stage at which the product just becomes lumpy is called Critical point. A point which has 5% lower RH than the critical point is called Danger point. A portion of curve between danger point (D) and critical point (C) is called Safety range.

Exhausting: Removal of air from the head space of filled container either by heat treatment or mechanical method is called exhausting. It is removal or air from within and around food, jars and canners. Blanching exhausts air from the food tissue.

Flavonoids: These are 15-C compounds (C₆-C₃-C₆) consisting, of the two aromatic rings linked by an aliphalic three carbon chain and often synthesized in the chloroplasts. The hydroxylation pattern and degree of polymerisation of the C6-C3-C6 unit result in different polyphenolic compounds. The major flavonoids are anthocyanins, flavonols and flavones. These are white and cream coloured plant pigments of potatoes.

Food additive: Food additive is defined as a substance or a mixture of substances other than the food stuff incorporated in food either directly or indirectly as a result of any phase of production, processing, storage or packaging to improve or maintain the nutritional value, enhance quality, consumer acceptability and facilitate the preparation of materials e.g., acid, alkali, bleaching agents, emulsifying & sterilizing agents, flavours, colours, nutrient supplements, clarifying agents, humectants, chemical preservatives etc.

Glucose oxidase: Glucose oxidase is an enzyme that breakdown glucose and help in prevention of non enzymatic browning reactions. Glucose is breakdown to gluconic acid by Glucose oxidase

Heat processing:  The fundamental principle of preserving food by application of heat is called heat processing. It is a heat treatment to which the foods are subjected after hermetic sealing in containers is called heat processing.

Hermetically seal container: it is an absolute airtight container seal, which prevents entry of air or microorganisms into packed foods.

Inversion: The conversion of dextrorotatory sucrose into a levorotatory mixture of glucose and fructose.

Invert sugar: A mixture of dextrose and laevulose found in fruits or produced artificially by the inversion of sucrose.

Low acid foods: These are the foods having pH > 4.6 and processed above 100⁰C. The acidity in these foods is not sufficient to prevent the growth of the bacterium Clostridium botulinum.

Lye peeling: Peeling of fruits (peach, apricot,  orange etc) and vegetable (carrot, sweet potato etc) by dipping them in boiling lye solution (caustic soda) of 0.5-2% strength for short period (<30 second - 2 minutes) depending on the maturity and nature of fruits and vegetables to loose the skin from the flesh underneath to facilitate easy peeling.

Maillard reaction: The reactions between (i) nitrogenous compound and sugars (ii) nitrogenous compound and organic acids (iii) sugars and organic acids (iv) among organic acids themselves are known as maillard reaction. It may be independently causing browning of products which is of great important to food preservation techniques. It is difficult to control and also known as non enzymatic browning. Maillard reactions occur between reducing sugars, proteinaceous materials; is a major quality problem in dried and concentrated fruit products.

Non enzymatic browning: Non-enzymatic browning reactions are responsible for the colour and flavor of foods. Roasting of potatoes, toasting of biscuits, baking of breads and cakes produces a golden brown colour. Sometimes this reaction produces a desirable flavor (the chocolate flavor of cocoa beans) at other times the reaction is responsible for browning in foods. On heating the sugars undergoes ring opening, enolisation dehydration, and fragmentation into unsaturated carbonyl compounds. Heat induced browning reactions can be divided into two groups maillard reaction and carmalizaton.

Non-reducing sugars: Recuing sugars which are locked up in a glycosidic linkage are said to be non-reducing e.g. sucrose, maltose. Or When two or more monosaccharides are linked together through their aldehyde or ketone group so that their reducing groups are not free.

Peroxide value: The rancidity of the oil due to oxidation of the fatty acid is determined in term of peroxide value. It is also called lea value.

pH: It is a quantitative measure of strength of the acidity or alkalinity of a solution, defined as the negative logarithm (-log¹⁰) of the hydrogen ion concentration [H⁺] in moles/litre: pH = −log₁₀ [H⁺]. A measure of acidity or alkalinity which is expressed as the negative log of the hydrogen ion conc., pH of 7.0 is neutral, less than 7.0 is acidic and more than 7.0 is alkaline.

Polyphenol oxidase: An enzyme causing oxidation of phenols or polyphenols which maybe the principal reaction in enzymatic browning. Removal of O₂ by blanching or sulphiting of materials or deaeration of juice can help to prevent the activity of this enzyme.

Processing: The heating of the foods for preserving is known as processing. However in the canning, processing means heating or cooling of the canned foods to inactivate bacteria. Fruits are processed at a temperature of 100^oC while non acidic vegetables are processed at 115-121^oC.

Reconditioning: The exposure of the cold stored potatoes or onions to a temperature of 22±2^oC for 2-3 weeks prior to processing is known as reconditioning. It helps conversion of sugars formed during cold storage into starch and thus prevents non-enzymatic browning. For prolonged winter storage the potatoes are kept in the darkness at low temperature (4-5^oC) and high RH (80-90%). However, this favours a slow breakdown of the potato starch to sugar. For the manufacture of potato chips, high sugar content would result in excessive browning upon frying, which can be avoided by a reconditioning treatment. Reconditioning helps in using up the sugars and their conversion back to starch.

Reducing sugars: Sugars possessing a free aldehyde or ketone group e.g. maltose, glucose etc. Reducing sugars in many cases are responsible for undesirable browning during processing.

Refractometer: It is an instrument for measuring refractive indices of food commodities for determination of total soluble sugars. Or Refractometer is an instrument used to determine the refractive index of liquids. It is employed as a production line tool. Total soluble solids are estimated by this instrument. It requires 2-3 ml of the sample for estimation.

Soxhtec: It is an apparatus used for the estimation of the oil in the food sample. In this apparatus a small amount of the sample is required as compared to soxhlet apparatus. Petroleum ether is used as solvent during estimation of oil content  

Starch: It is an insoluble crystalline substance in the natural form. Starch is a long chain molecule of glucose polymer. Starch is a straight chain molecule of amylose having 200-10000 subunits of glucose & amyl pectin. Starch is also seen in branched form i.e., minimum of 2000-200,000 glucose units. The ratio between the amylase and amyl pectin in a particular species /type is genetically controlled by amyl pectin comprising of 60-95%.

Suberization: It is the process of developing of secondary skin for protecting potatoes against rotting/ microbial spoilage. It is process of conversion of the cell walls into corky tissue by infiltration with suberin.

Sulphitation: Treatment of the prepared and blanched potatoes with potassium metabisulphite solution either by dipping or spraying for sufficient time. Generally 0.2% KMS solution helps to achieve all benefits.

Sweating: The process for equalization of the moisture content of the dried products is called sweating. Sweating is the equalization of moisture to a desired level of the dried fruit and nuts before packaging.

Thermal fogging: The volatile chemicals can be applied as a vapour which is circulated in a confined space containing the crop. Some chemicals need to be heated to aid circulation and this process is thermal fogging. CIPC also called chloropropham is applied as thermal fog.

Value addition: It is process by which a fresh commodity is altered in such a way that it offers great convenience for handling, transportation, storage and consumption. It may or may not involve processing or addition of various additives but must definitely add to its nutritional value and economical returns.