CARBOHYDRATES IN FOOD ANALYSIS

M.pharm 1 semester notes

1. DEPARTMENT OF PHARMACEUTICAL ANALYSIS R.R JAYARAJ ( M.pharm ) K.K college of pharmacy FOOD ANALYSIS

2. CARBOHYDRATES

3. Carbohydrates are broadly defined as polyhydroxy aldehydes or ketones and their derivatives or as substances that yields one of the compound . Composed of carbon, hydrogen, and oxygen. Carbohydrates include sugars, starches, cellulose, and glycogen. Carbohydrates serves as a primary source of energy and needed for storage and liberation of energy. Carbohydrates are the most abundant organic compounds in the plant world. GENERAL INTRODUCTION

4. They are used as material for  energy storage and production. They exert a protein-saving action Their presence is necessary for the  normal lipid metabolism.  Glucose is indispensable for the maintenance of the integrity of nervous tissue Two sugars, ribose and deoxyribose , are part of the bearing structure, respectively of the RNA and DNA and obviously find themselves in the nucleotide structure as well. They take part in detoxifying processes FUNCTIONS OF CARBOHYDRATES

5. CLASSIFICATION

6. CLASSIFICATION

7. Single sugar unit = monosaccharide ex: glucose = primary animal energy source  Two sugar units = disaccharide ex : lactose = milk sugar 5 units or more = oligosaccharide or polysaccharide ex: amylose = starch CLASSIFICATION

8. Monosaccharides   are water-soluble crystalline compounds . They are aliphatic aldehydes or ketones which contain one carbonyl group and one or more hydroxyl groups . Most natural  monosacharides  have either five ( pentose) or six (hexoses) carbon atoms. Commonly occurring hexoses in foods are glucose, fructose and  galactose , which commonly occurring  pentose  are arabinose and xylose . The reactive centers of  monosaccharides  are the carbonyl and hydroxyl groups.   monosaccharides

9. Oligosaccharides  are formed by short chains of monosaccharidic units (from 2 to 20) linked one to the next by chemical bounds, called glycosidic bounds. The most abundant oligosaccharides are disaccharides, formed by two monosaccharides , and especially in the human diet the most important are sucrose (common table sugar), lactose and maltose. Within cells many oligosaccharides formed by three or more units do not find themselves as free molecules but linked to other ones, lipids or proteins, to form glyco conjugates . oligosaccharides

10. Polysaccharides   are polymers consisting of 20 to 10 7   monosaccharide units. They differ each other for the monosaccharides recurring in the structure, for the length and the degree of branching of chains or for the type of links between units. Whereas in the plant kingdom several types of polysaccharides are present, in vertebrates there are only a small number polysaccharides

11. PROPERTIES OF FOOD CARBOHYDRATES

12. The word hygroscopic means water attracting. Sugar absorbs moisture from air ,when it is exposed to air and are known to be very hygroscopic in nature ,hence sugar should be stored in airtight container. Sugar tend to absorb moisture and sticky when exposed to air. 2 . SOLUBILITY Sugar are soluble carbohydrates. The solubility decreases as the sugars come together ,as often happens in sugar powders or granulates. The sugar arranged in descending order of solubility are fructose , sucrose, glucose, maltose and lactose. This property is important to obtain a particular product when mixture of sugar is used. 1.HYGROSCOPIC NATURE

13. The ability of sugar to dissolve and reform crystals. Sugar is dissolved in a liquid and heated, the liquid evaporates, concentrating the sugar solution . As the solution cools ,the sugar re-form into crystals. Crystals of sugar thus obtained are very desirable in sugar coated preparations like sugar coated nuts and other such as icings and candies. Crystallization depends upon a number of factors include, nature of the crystallizing medium, concentration of sugar in the preparation, temperature ,addition of other ingredients , such as butter, ghee, egg etc. 3.CRYSTALLIZATION

14. When starch is mixed with water and heated the starch granules swell and eventually rupture, absorbing liquid which thickens the mixture. On cooling, if enough starch is used , a gel forms. Gelatinization can take place in different temperature range, commonly it take place at 88⁰C – 90⁰C. Common thickening agents : plain wheat flour, corn flour etc. Two factors affect the qualities of the gel produced. These are the ratio of amylose to amylopectin and the method used to prepare the food . 4.GELATINIZATION

15. Gelation is the method of solidification mainly through freezing is the creation of gel or the solidification of any gelation solution. The gelatin is used for gelation. The gelatin liquid form a thick sugar solution and constantly thickens when freezed . There is no any definite setting point. In some food gel is produced on cooling and in some it may be formed on heating. Gels can either be thermo-irreversible or thermo reversible, it all depends on the type of gelation occurred. EXAMPLE: cooling- gelation in gelatin, heating- egg white. 5.GELATION

16. Viscosity is a fluid’s resistance to flow or fluid thickness. The thicker the liquid, more is its viscosity. The viscosity of a fluid can be measured by 1. Seeing how far a fluid can flow down an incline. 2. Viscometer- measures the force necessary to move through a liquid. 3. Household instruments- measuring how far a liquid can move on a slight incline after a certain amount of time. Measuring of viscosity is to determine how resistant that material is to following 1. Flow down a slight incline very quickly – very little resistance to flow. 6.VISCOSITY

17. 2. Lot of force to move through a liquid, it has a lot of resistance to flow. • A fluid will be more resistant to flow the more internal friction it has. • Many food industries check for vicosity . There is an acceptable range of vicosity if it is not in the range then it will not be sold. CONTINUED

18. Colloidal are formed when one substance is dispersed into another, but does not combine to form a solution. There are many types of colloidal systems based on the state of two substances mixed together. GEL,SOLUTION, FOAM AND EMULSIONS. Most colloidal are stable, but the two substance may separate over a period of time because of an increase in temperature or by physical force. Sometime will be unstable when frozen or heated, especially if they contain emulsion of fats and water. 7.COLLOIDAL PROPERTY

19. Sol and gel both are liquid loving colloids Sol- solid particles are dispersed in liquid phase when, the mixture is heated or cooled the sol changes to gel, which resembles solid rather than a liquid. continued

20. OIL+ WATER= EMULSION Emulsion is unstable. The two liquids are immiscible. A stable emulsion is formed when two immiscible liquids are held stable by a third substance called as an Emulsifying agent. There are two type of emulsifying agent, HYDROPHILIC (water loving) and HYDROPHOBIC ( water hating). Emulsion may be 1. oil-in-water(o/w) – small oil droplets in water(milk) 2. water-in-oil(w/o) – small water droplets in oil (butter ) 8.EMULSION

21. When small bubbles of gas dispersed in a liquid they form foaming . EXAMPLE : egg white foam, as air bubbles get incorporated . If egg white is heated, protein coagulates and moisture is driven off. This form a solid foam . 9.FOAMING

22. METHOD OF ANALYSIS

23. Carbohydrate content can be measured after all other components are measured But! This can lead to erroneous results Instead , Directly measure the carbohydrate content METHODS OF ANALYSIS

24. Monosaccharide and Oligosaccharides Prior to Analysis: Sample Preparation Amount of preparation depends on the nature of the food Aqueous solutions require little preparation But! Physically Associated or Chemically Bound need to be isolated Method of Isolation depends on the : 1. Carbohydrate type 2 . Food Matrix Type 3. Purpose of the Analysis CONTINUED

25. Example: Sample Preparation

26. 1. Boil a defatted sample with 80% alcohol solution • Mono & Oligo – soluble in alcoholic solutions • Poly & Dietary Fibers – insoluble 2. Separate the component by filtering the boiled solution • Filtrate and Retetnate 3. The two fractions are dried and weighed Note! • Filtrate may contain small molecules (Amino acids, Organic Acids, Pigments , Vitamins, Minerals) Have to be remove prior analysis by treatment of Clarifying Solutions or Ion-Exchange Resins • Alcohol can be removed by evaporation under vacuum Extracting Low Molecular Weight Carbohydrate

27. 1.Chromatographic and Electrophoretic methods 2. Chemical methods 3. Enzymatic methods 4. Physical methods 5. Immunoassays METHODS OF ANALYSIS

28. Most powerful analytical techniques Analysis of Type and Concentration of Mono and O ligo Commonly used to separate and identify carbohydrates 1. Thin Layer Chromatography, TLC 2. Gas Chromatography, GC 3. High Performance Liquid Chromatography, HPLC Carbohydrates are separated base of their differential absorption characteristics Chromatographic Methods

29. Carbohydrates are separated by electrophoresis after being derivitized –make them electrically charged Solution of derivitized carbs is applied to a gel and a voltage is applied across t he carbohydrates are then separated base of their size The smaller the size – faster it moves in an electrical field Electrophoretic Methods

30. These methods are used to determine Mono & Oligo because most of them are reducing sugars Concentration of carbohydrates can be determined: 1. Gravimetrically (Gravimetric Methods) 2. Spectrophotometrically (Colorimetric Methods) 3. Titration Methods Note! Non-reducing carb can be determined but they have to be hydrolyzed CHEMICAL METHODS

31. They base on the ability of the enzymes to catalyze specific reactions These methods are rapid, highly specific, sensitive to low concentrations Little sample preparation is required – Liquid Foods – can be tested directly – Solid Foods – dissolved in water Two commonly used methods 1. Allow the reaction to complete and measure the concentration of the product Concentration of the product – Concentration of the Initial Substrate 2.Measure the initial rate of the enzymes catalyzed reaction Rate - Substrate Concentration Enzymatic Methods

32. These methods rely on being a change in physiochemical characteristics as its carbohydrate concentration varies Commonly Used 1. Polarimetry 2. Refractive Index 3. Infrared 4. Density Physical method

33. Specific for low molecular weight carbohydrates • Developed by 1. Attaching the carbohydrate to a protein 2. Injecting it into an animal 3. Animal develops antibodies specific for the carbohydrate molecule 4. Antibodies are extracted and used for determining the concentration of the carbohydrate Immunoassays are extremely sensitive, specific, easy to use, and rapid Immunoassays

34. Test objective Molisch test To identify the carbohydrate from other macromolecules lipids and proteins Benedict's test Benedict's reagent is used as a test for the presence of reducing sugars. Barfoed’s Test To distinguish between reducing monosaccharides , reducing disaccharides and non reducing disaccharides. Bial’s Test To distinguish between pentose monosaccharide and hexose monosaccharide Seliwanoff's Test To distinguish between aldose and ketone sugars

35. EFFECTS OF FOOD PROCESSING ON DIETARY CARBOHYDRATES

36. Low molecular weight carbohydrates: During wet heat treatment, as in blanching, boiling and canning of vegetables and fruits, there is a considerable loss of low molecular weight carbohydrates (i.e. mono- and disaccharides) as well as micronutrients, into the processing water . The loss of glucose and fructose at boiling will be higher than that of sucrose. Dietary fibre No leaching of dietary fibre into the processing water has been reported with blanching, boiling and canning of carrots, green peas, green beans and Brussels sprouts. T here was a 40% loss of dietary fibre (mainly insoluble) with boiling. Carbohydrate loss through leaching

37. Maillard reactions Non-enzymatic browning reactions ( Maillard reactions) occur between reducing sugars and amino groups in foods at processing and in storage. These reactions are temperature dependent and most extensive at intermediate water activities. When a non-reducing disaccharide such as sucrose is replaced by, for example, high fructose corn syrup containing glucose and fructose, Maillard reactions occur much more rapidly and extensively . Starch heat-induced effects Gelatinization refers to the irreversible loss of the crystalline regions in starch granules that occur upon heating in the presence of water. The temperature range during which the crystalline structure of the starch granule is lost is dependent on the water content, and on the type of starch.

38. Retrogradation Gelatinized starch is not in thermodynamic equilibrium. There is, therefore, a progressive re-association of the starch molecules upon ageing . This recrystallization is referred to as retro gradation, and may reduce the digestibility of the starch Par-boiling During par-boiling of rice, the kernels are subjected to a pre-treatment involving heating and drying. This process reduces the stickiness of the rice, possibly by allowing leached amylose to retrograde and/or form inclusion complexes with polar lipids on the kernel surface. Parboiling also affects the final cooking properties of the rice.

39. Starch texturization In pasta products, gluten forms a viscoelastic network that surrounds the starch granules, which restricts swelling and leaching during boiling. Dietary fibre Milling and peeling During milling of cereal grains to refined flours the outer fibre -rich layers are removed, resulting in a lower content of total dietary fibre . This reduction is due mainly to a decrease of insoluble fibre

40. Heat-treatment Processes involving heat-treatment may affect the dietary fibre in different ways. An increased temperature leads to a breakage of weak bonds between polysaccharide chains. Also glycosidic linkages in the dietary fibre polysaccharides may be broken . Hydration properties (swelling, water-holding and water-binding capacity) Most raw materials containing cereal fibres are ground for better acceptance of the final product and this process can affect hydration properties. Swelling and water-binding capacity of pea hull fibres are decreased by grinding, whereas the water-holding capacity was slightly increased .

41. DIGESTION,ABSORPTION AND METABOLISM OF CARBOHYDRATES

42. Carbohydrates are most commonly consumed as polysaccharides (e.g. starch, fibre or cellulose) or disaccharides (e.g. lactose, sucrose, galactose ) and therefore need to be broken down into their simpler monosaccharide forms which the body can utilise . The digestion process of polysaccharides such as starch will begin in the mouth where it is hydrolysed by salivary amylase. The amount of starch hydrolysed in this environment is often quite small as most food does not stay in the mouth long. Once the food bolus reaches the stomach the salivary enzymes are denatured. As a result, digestion predominantly occurs in the small intestine with pancreatic amylase hydrolysing the starch to dextrin and maltose. Enzymes classed as glucosidases on the brush border of the small intestine break down the dextrin and maltase, lactase and sucrase convert the other disaccharides into their two monosaccharide units . Digestion

43. Absorption & transport The monosaccharide units, glucose, galactose and fructose are transported through the wall of the small intestine into the portal vein which then takes them straight to the liver. The mode of transport varies between the three monosaccharides and is described in brief below. Both glucose and fructose are absorbed relatively quickly, depending on what other nutrients are eaten at the same time. For example a meal or food containing protein and fat causes the sugars to be absorbed slower than when consumed on their own.

44. Carbohydrates are used in pharmacy: For the preparation of simple syrup(sucrose) As diluent and binders for the preparation of tablets (lactose and starch) For the preparation of infants’s food (starch and dextrin) For the preparation sterile I V solution (dextrose) In antidiarrheal drugs (pectin) Starch, sugar, gums& pectins are used as thickening agents in making jams, cakes , cookies, noodles and variety of other foods In food industry both fast releasing and slow releasing carbohydrates are used. Adding fibrer to foods increase bulk APPLICATION OF CARBOHYDRATES IN FOODS

45. Starch, sugar, gums& pectins are used as thickening agents in making jams, cakes , cookies, noodles and variety of other foods In food industry both fast releasing and slow releasing carbohydrates are used. Adding fibrer to foods increase bulk S imple sugars are used as sweetening agent, consisting agent and browning.

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