Introduction to food science.pdf

INTRODUCTION TO FO O D SCIENCE FOOD SCIENCE The study of the chemical, physical and microbiological nature of foods and any P R E S E N TAT I O N T I T L E transformation that food undergoes as reflected in its...

INTRODUCTION TO FO O D SCIENCE FOOD SCIENCE The study of the chemical, physical and microbiological nature of foods and any P R E S E N TAT I O N T I T L E transformation that food undergoes as reflected in its characteristics and properties. 2  FOOD SOCIO- P H YS I O LOG I C A L B I O LO G I C A L C U LT U R A L P R E S E N TAT I O N T I T L E Any substance which Any substance Any substance when taken into the when eaten that satisfies the body provides energy, human senses sustains life and builds and repairs tissues and regulates nourishes the as well as bodily processes body. emotional needs 3 FOOD QUALITY A composite of several criteria determined by the stimuli coming from the food itself as well as P R E S E N TAT I O N T I T L E attitudes attached by the consumer to the food; includes nutritional quality, digestibility, palatability, economy and sanitary quality. 4  ASPECTS OF FOOD QUALITY Nutritional Quality - Food are sources of nutrients grouped as water, carbohydrates, proteins, fats, vitamins and minerals Digestibility - Refers to completeness of digestion and absorption; general feeling and after effect feeling of food Palatability factors - Eating quality of a food as judged by the human senses  ASPECTS OF FOOD QUALITY Economy in the use of resources – considers food cost, amount of time, equipment and labor utilized for cooking, serving and storing the food Sanitary quality – free from any other forms of contamination that are hazardous to human health, i.e microbiological, biological, chemical, physical and radiological Food-borne illness/ disorders a. Food intoxication b. Food infection  CHEMICAL COMPOSITION OF FOOD (1)Macronutrients  Carbohydrates, Proteins, Fats, Water (2)Micronutrients  Vitamins and Minerals (3)Non-nutritional components  Pigments, Enzymes, gums, organic acids, tannins, esters, ketones and other flavoring compounds  W AT E R Most common dispersing medium Most abundant compound in food May be present in foods in 5 forms: (1) free water (2) hydrates (3) adsorbed on the surfaces of solids/ crystals (4) absorbed or imbibed within gels and (5) bound water  PROTIEN  Organic compounds composed of amino acids linked by peptide bonds; contains nitrogen  Essential Amino Acids  Non-essential Amino Acids  May be classified as:  Simple  Conjugated  Derived  PROTIEN  Complete Proteins – animal foods such as meat, poultry, fish, shellfish, milk (cheese, yogurt), and eggs  Incomplete Proteins – plant sources (grains) except legumes  PROTIEN FUNCTIONS IN FOOD: (1)Hydration  Can form a gel  Due to gelling ability  Its hydrating ability (2)Denaturation (3)Enzymatic reactions  PROTIEN USEFUL APPLICATION OF ENZYMES IN FOODS:  rennin/ chymosin – aids in cheese production, converting milk to curd  Papain, bromelain, ficin – meat tenderizers  Pectinase, cellulose, hemicellulose, amylase, arabinase – used in fruit juice processing to increase the yield, enhance juice clarity, improve filtration, reduce bitterness, and hasten fruit dehydration  PROTIEN  Invertase – used to facilitate sucrose inversion needed in making confections like soft chocolate centers of candies  Amylase – used to split starch in flour when making bread to produce fermentable sugars to be acted upon yeast  Pectinases- responsible for ripening of fruits by changing protopectin to pectin and pectic acids  Microbial enzymes – responsible for fermentation and proteolysis  PROTIEN Undesirable Reactions of Enzymes in Foods:  Enzymatic Browning – the enzymes act on a phenolic compound in the presence of oxygen to produce brown-colored products  Rancidity of gats and oils as butter, coconut oil, and fat-rich foods like nuts, wheat germ, rice bran, bacon  Maturation of vegetables  Spoilage of foods as in putrefaction of fish and meat or decaying of fruits and vegetables  C A R B O H Y D R AT E S  Synthesized by photosynthesis  Hydrates of carbon and can be expressed as CHO  Based on structure, the two main groups are sugars and polysaccharides  Sugars include the monosaccharides and disaccharides  Monosaccharides (glucose, fructose and galactose)  Disaccharides (sucrose, lactose and ,maltose)  C A R B O H Y D R AT E S  Polysaccharides are further divided into:  Digestible (starch, dextrins and glycogen)  Partially digestible (galactogens, inulin, mannosans, and pentosans)  Indigestible (cellulose, hemicellulose like agar and pectin, lignin)  Polysaccharides commonly used in the food industry are fiber, vegetable gums and pectic substance  C A R B O H Y D R AT E S Soluble vs. Insoluble Fiber: a. Soluble fibers – help lower high blood cholesterol levels and reduce high blood glucose b. Insoluble Fibers – absorb water, thus increasing the softness and bulk of the stool to prevent constipation Foods high in Soluble fiber: dried beans, peas, lentils, oats rice bran, barley and oranges Foods high in Insoluble fiber: whole wheat (wheat bran), rye products  FA T S Organic compounds belonging to water soluble substances called lipids Esters of glycerol and fatty acids Fatty acids are either saturated and unsaturated Fats have a greasy feel Fats are solid on room temperature (composed of saturated fats) Oils are liquid (composed of unsaturated fats)  FA T S lipids do not dissolve in water but dissolve in organic solvents (benzene, chloroform, ether, acetone) Fats are from animal sources, while Oils are from plants (except for coconut, and palm oils which are solid in room temp; fish oils are liquid at room temp.) Three groups of Lipids are: Triglycerides (fats & oils); Phospholipids; Sterols  FA T S TRIGLYCERIDES Saturated fatty acids – present in animal foods (meat, dairy products like milk and butter) and in plant food like coconut, coconut oil and palm oil Unsaturated fatty acids – present in plant foods (olives, olive oil, peanuts, peanut butter, avocado)  FA T S  TRIGLYCERIDES Polyunsaturated fatty acids – present in plant foods (vegetables oils, fish) Omega-3 Fatty Acid or linolenic acid Omega-6 Fatty Acid or linoleic acid  C H E M I C A L D E G R A DAT I O N O F FA T S  Rancidity  Oxidative Rancidity  Antioxidants  Hydrolytic rancidity  Reversion  Smoke Point  Acrolein  Acrylamide  MINERALS Inorganic constituents collectively called as ash. There are 17 nutritional minerals, namely: calcium, P R E S E N TAT I O N T I T L E phosphorous, potassium, sulfur, sodium, chlorine, magnesium, iron, zinc, manganese, copper, selenium, iodine, molybdenum, cobalt, chromium and fluorine. 23  V I TA M I N S Organic compounds classified as either water soluble (B-Vitamins) or fat-soluble vitamins.  NON-NUTRITIONAL COMPONENTS PIGMENTS In plants includes chlorophyll and carotenoids which are fat soluble and flavonoids and tannins (anthocyanins anthoxanthins) which are water soluble. In animals, hemoglobin int blood and myoglobin in the muscle, riboflavin and sepia.  ENZYMES Organic catalyst that are protein in nature Useful applications of enzymes in foods include: Meat tenderizers Sugar inversion  F L AVO R C O M P O N E N T S Substances responsible for the four primary tastes include sugars, acids, aldehydes, esters, alcohols, ketones and sulfuric compounds. Volatile acids – partly responsible for aroma of fruits and some root crops. Non-volatile acids – those do not change to vapor state even when heating.  B R O W N I N G R E AT I O N S O N FOODS Enzymic or non-enzymic reactions encountered in some foods and food products resulting in desirable effects to some and undesirable effects to others.  Non-enzymic purely chemical reactions in nature 1. Caramelization – non-enzymatic browning reaction associated with heating.  B R O W N I N G R E AT I O N S O N FOODS 2. Maillard Browning reaction – non-enzymatic browning reaction between the free aldehyde group in the sugar molecule and the amino group in protein and other compounds found in foods.  Enzymic – biochemical reactions involving enzymes. 1. Oxidation reaction of polyphenols (anthocyanins, tannins, anthoxanthines and flavones) 2. Ascorbic Acid Oxidation (Vitamin C Oxidation)  W AY S O F R E D U C I N G O R PREVENTING BROWNING REACTIONS IN FOODS 1. Prevention of contact with air or oxygen such as wrapping or soaking in water 2. Use of salt 3. Use of acid 4. Blanching 5. Refrigeration 6. Use of anti-oxidants  DISPERSION Combinations of dispersed particles scattered throughout a dispersion medium resulting in a homogenous or heterogeneous mixtures May be gas, liquid or solid; dispersion medium is usually liquid or solidified liquid. Categories of dispersion: true solutions, colloidal dispersion and suspension  TYPES OF DISPERSION  True Solution – a homogenous mixture which looks transparent, exhibits high osmotic pressure and consists of very small particles invisible under an ultra-microscope.  Colloids – two phased systems in which the particles are visible in an ultra-microscope and do not have osmotic pressure.  FOUR COMMON TYPES OF C OLLOIDA L SYSTEM IN FOOD S (a) Sol – a liquid gel; dispersed phase is solid and the dispersing medium is liquid like (b) Gel – solidified sol like custards, gelatin, jellies (c) Emulsion – liquid dispersion in another liquid with wich is immiscible like oil-in-water emulsion (oil is dispersed in water) (d) Foam – gas dispersed in a liquid or solid medium; e.g. liquid foams (beaten egg whites, whipped cream), solid foams (marshmellows, gelatin, sponge and meringues)  TYPES OF DISPERSION Suspension – mixtures which may separate on standing and will not gel; consist of large particles scattered in the liquid.  H E AT I N C O O K I N G HEAT  A form of energy due to the vibratory or kinetic movement of molecules; its intensity (hotness) is measured by degrees Centigrade or Celsius and degrees Fahrenheit  H E AT I N C O O K I N G COOKING  The process and techniques of using food or combinations of food as to achieve a product which is edible, palatable, aesthetically pleasing, nutritious and microbiologically safe with the application or removal (by freezing) of heat.  GENERAL METHODS OF COOKING (a)Moist Heat – Cooking food with water or liquids like boiling, stewing (b)Dry Heat – cooking food with little or no liquids at all like frying, broiling, grilling, baking  M O D E S O F H E AT T R A N S F E R 1. Conduction – the direct transfer of heat via metals or any heat conducting materials containing the food. Copper has the highest rate of conductivity while glass is the poorest. 2. Convection – transfer of thermal energy from electricity, gas or solid fuel to the vapor molecules of the air which in turn heat the food or the utensil it comes in contact with.  M O D E S O F H E AT T R A N S F E R 3. Radiation – transfer of heat from a red coil of the griller, toaster or stove to the food 4. Microwave – heat transfer that uses electromagnetic waves generated by the magnetron. Microwaves are radiated energy and have longer wavelengths than infra-red waves  PH IN FOOD  Refers to the acidity and basicity of food  Applications of pH in food preparation and processing  Gel formation in jellies occurs at pH 3.2  A dough with pH 5 results in good volume and texture  Biscuits with pH 7 are crispy and cream-colored  PH IN FOOD  Applications of pH in food preparation and processing  Acidic foods are pasteurized while basic foods are usually sterilized  Acidic pH is not conductive for the growth and survival of many types of microorganisms  Acids contribute to sourness of foods PHYSIC O - C HEM IC A L C HA NGES IN FOOD Sensory attributes of food include appearance, shape, color, aroma, consistency/ texture, flavor, etc.  E F F E C T O F H E AT T R E AT M E N T Protein – heat causes coagulation and eventual denaturation of protein in foods like meat, fish, eggs, poultry, e.g: scrambled or fried egg Fats – fats can be removed or absorbed/ over heating results in the formation of acrolein which is the characteristic flavor of burnt oil.  E F F E C T O F H E AT T R E AT M E N T Starch – with water when heated results in an increased in viscosity in the process called gelatinization (moist cooking) and therefore, is useful for thickener or binder. Sugar – sucrose added to water raises boiling point. At 160 degrees Celsius, the sucrose concentration is 100%; at above 160 degrees Celsius, sugar melts and sucrose changes color from white to brown, a characteristic of caramelized sugar. Crystallization is a process when, in the presence of a nucleus, small crystals of sugar are formed during candy-making  EFFECT OF COLD Temperature change of food from room to cold to frozen affects both the functional and eating qualities of food such as difficulty on separating egg white from the yolk; meat improves in tenderness and flavor when frozen.  EFFECT OF ACID Chlorophyll changes into undesirable olive-green color; too acidic jelly will result in syneresis; viscosity and texture are affected such as vinegar and citric acid reduce the thickness of the hot starch paste and the firmness of the cooled paste.  PHYSIC A L A ND M EC HA NIC A L T R E AT M E N T 1. Agitation and stirring - 2. Whipping or beating – introduces air into a mixture resulting in tenderness and greater stability as foam cakes 3. Kneading – allows the alignment of the gluten network resulting in tenderness in baked products and allows gas produced by the yeast during fermentation to get trapped in the gluten network which is responsible for the volume of the bread when baked. T H A N K YO U