Different measurements in food science
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This document discusses different measurement techniques used in food science, including density, phase change, pH, osmosis, surface tension, and colloidal systems. It provides definitions and examples for each measurement. Density is defined as mass per unit volume and is represented by the Greek letter p. Phase changes refer to changes in state, such as freezing or boiling water. pH is defined as the negative logarithm of hydrogen ion concentration and is measured using a pH meter. Osmosis and reverse osmosis describe the diffusion of solvent molecules across a semi-permeable membrane, with or against a concentration gradient. Surface tension is the force per unit length at a liquid's surface. Colloidal systems have particle sizes between true
Different measurements in food science
- 1. FOOD SCIENCE AND NUTRITION DIFFERENT MEARUREMENTS USED IN FOOD SCIENCE-DENSITY,PHASE CHANGE,pH,OSMOSIS,SURFACE TENSION,COLLOIDAL SYSTEMS.
- 2. DENSITY: A MATERIAL’S DENSITY IS DEFINED AS ITS MASS PER UNIT VOLUME. HYDROMETER IS AN INSTRUMENT USED FOR DETERMINING THECDENSITY OF A LIQUID. REPRESENTED BY THE GREEK LETTER “p”. P=m/v SI UNIT OF DENSITY IS KILOGRAM PER CUBIC METER
- 3. PHASE CHANGE: • PHASE CHANGE REFER TO A CHANGE IN MATTER FROM ONE STATE TO ANOTHER. • THE MOST FAMILIAR PHASE CHANGES ARE SEEN IN THE DIFFEENT STATES OF WATER,SUCH AS FREEZING LIQUID WATER TO CREATE ICE OR BOILING LIQUID WATER TO CREATE A GAS. • THE HEAT PLAYS MAJOR ROLE IN CHANGING MATTER FROM ONE PHASE TO ANOTHER
- 5. pH: • pH IS DEFINED AS THE NEGATIVE LOGARITHIMIC OF H+ ION CONCENTRATION. • pHSCALE RANGES FROM 0 TO 14 IN THE SCALE. • pH HAS DIRECT ROLE IN PROLONGING SHELF LIFE OF PRODUCTS. • THE pH METER MEASURES ACID CONCENTRATION. • Yeast-4-4.5pH,moulds- 4pH,bacteria-7pH.
- 6. pH:
- 7. CLASSIFICATION OF FOODS ON THE BASIS OF pH: A)LOW ACID FOODS:pH OF 5 AND HIGHER. THIS INCLUDES PEAS,MAIZE,CORN,CAULIFLOWER,POTATO,SPINACH,BEANS etc. B)MEDIUM ACID FOODS:pH OF 5 TO 4.5.THIS CLASS INCLUDES MEAT AND VEGETABLE MIXTURES,SOUPS,SAUCES,FISH CARROT,OKRA,CABBAGE etc. C)ACID FOODS:pH OF 4.5 TO 3.7.THESE INCLUDE INCLUDETOMATOES,PEARS,PINEAPPLE,BANANA,MANGO etc. D)HIGHLY ACIDIC FOODS:pH IS 3.7 AND BELOW.THIS INCLUDES PICKLES,CITRUS JUICES,RHUBARB,PRUNE,CHUTNEYetc. The pH above 4.5 required processing at a temperature of 118-121°c to keep it fit for cinsumption and avoids microbial activity.
- 8. OSMOSIS: IF TWO SOLUTIONS OF DIFFERENT CONCENTRATIONS ARE SEPERATED BY A SEMI-PERMIABLE MEMBRANE WHICH IS PERMIABLE TO THE SMALLER SOLVENT MOLECULES BUT NOT TO THE LARGER SOLUTE MOLECULES ,THEN THE SOLVENT WILL TEND TO DIFFUSE ACROSS THE MEMBRANE FROM THE LESS CONCENTRATED TO THE MORE CONCENTRATED SOLUTION.THIS PROCESS US CALLED OSMOSIS. EXAMPLES: OSMOSIS ARE WHEN PLANT ROOTS ABSORB WATER FROM THE SOIL AND OUR KIDNEYS ABSORB WATER FROM OUR BLOOD
- 9. REVERSE OSMOSIS: • REVERSE OSMOSIS IS THE PROCESS OF OSMOSIS IN REVERSE.TN REVERSE OSMOSIS THERE IS A NEED TO ‘PUSH’ THE LIQUID THROUDH THE REVERSE OSMOSIS MEMBRANE BY APPLYING PRESURE THAT IS GREATER THAN THE NATURALLY OCCURRING OSMOTIC PRESSURE WHEREAS OSMOSIS OCCURS NATURALLY WITHOUT ENERGY REQUIRED. • EXAMPLE:WHEN PRESSURE IS APPLIED TO THE CONCENTRATED SOLUTION, THE WATER MOLECULES ARE FORCED THROGHT THE SEMI-PERMIABLE MEMBRANE AND THE CONTAMINANTS ARE NOT ALLOWED THROGH.
- 10. OSMOSIS AND REVERSE OSMOSIS:
- 11. SURFACE TENSION: IT IS DEFINED AS THE DRAGGING FORCE IN THE GIVEN LIQUID PER UNIT LENGTH. T=F/L F=force per unit length,T=suface tension,L=length over which the force acts. Surface tension is expressed in newton per meter SPECIFIC GRAVITY: IT IS THE RATIO OF DENSITY OF A SUBSTANCE TO THE DENSITY OF REFERENCE MATERIAL.WHICH MEANS IT IS EXPRESSED AS MULTIPLES OF DENSITY OF OTHER STANDARD MATERIALS USUALLY WATER FOR SOLID MATERIALS AND AIR FIR GASES.
- 12. EXAMPLE: AN OBJECT WITH A SPECIFIC GRAVITY LESS THAN 1 WILL FLOAT IN WATER;WHILE A SPECIFIC GRAVITY GRATER THAN 1 MEANS IT WILL SINK. IT IS THIS WHICH ALLOWS,FIR EXAMPLE,A BALLOON FILLED WITH HOT AIR TO FLOAT IN RELATIONTO THE REST OF THE AIR. IT IS EXPRESED AS THE THE DIMENSIONLESS QUANTITY AND IS ALSO CALLED AS RELATIVE DENSITY. SPECIFIC GRAVITY =density of material/density of water(for solids). SPECIFIC GRAVITY=densityof gas/density of air(forgas) Density of water at 0°c is 1000Kg/m3 and at 50°c it is 987kg/m3. Aur has density of 1.29kg/m3 at 0°c and the value is 0.94kg/m3 at 100°c.
- 13. Colloidal systems: THE COLLOIDAL SYSTEMS OR COLLOIDAL DISPERTIONS ARE INTERMEDIATE BETWEEN TRUE SOLUTIONS AND SUSPENTIONS. In other words ,the diameter of the dispersed particles in a colloidal dispertion is more than that of solute particles in a true solution and smaller than of suspension. In a true solution as sugar or salt in water the sow partices are dispersed in the solvent as single molecules or ion.thus the diameter of the dispersed particles ranges from 1A°to 10A°.
- 14. COLLOIDAL SYSTEMS: • On the other hand in a suspention as sand stirred into water,the dispersed particles are aggregates of millions of molecule.the diameter of these particles isof the order of 2000 or more. Hydrophilic colloids make water unavailable. • When the diameter of the particles of a substance dispersed ina solvent ranges from about 10A°to 2000A°.the system is termed a colloidal solution, colloidal dispertion or simply a colloid. • A system with at least one dimension of the dispersed particles in the range 10A°-2000A°,is classed as a colloidal dispertion.
- 15. TYPES OF COLLOIDAL SYSTEM: • A Collidal systemis made of two phases. • The substance distributed as the collidal particles is called dispersed phase. • The second continuous solution of copper in water, copper particles are dispersed is called dispersed medium. • Example for a colloidal solution of copper in water,copper- dispersed phase,water-dispersion medium
- 16. FOAM,SOLS, EMULSIFICATION: FOAM:A colloidal system with aliquid or solid continuous phase and a gaseous dispersed phase. SOLS:Sols are colloidal systems in which a solid is dispersed in a liquid.these are sud divided into two classes. A)Lyophilic sols (solvent loving):these are those in which the smdispersed phase exibits a definite affinity of the medium or solvent.EXAMPLES:dispertions of starch gum and protein in water. B)lyophobic sols (solvent hating):these are those in which the dispersed phase has no attraction for the medium or the solvent EXAMPLE:sulphur in water EMULSIFICATION:creation of an emultion by the duspersion of one immiscible liquid in the form of small droplets in a second immiscible liquid.there are two typesof foid emulsions :oil-in-water and water-in- oil