CARBOHYDRATES IN FOOD

CARBOHYDRATES

Presented to:Dr. Shivesh SharmaPresented By:Shradha Suyal2015BT01

CARBOHYDRATES consist of C, H and O atoms.

are polyhydroxy aldehydes or polyhydroxy ketones, also called hydrates of Carbon.

most abundant & diverse class of organic compounds.

one of the three major macronutrients found in food.

critical role in proper functioning of the immune system, fertilization, blood clotting & human development.

found in a number of foods like fruits, starchy vegetables ( pea, potatoes), grains, milk, desserts, yoghurt etc .

They serve as

energy source, fuels and metabolic intermediates (starch, fructans, glycogen).

part of the structural framework of RNA and DNA.

structural elements in the cell walls of bacteria and plants, and in the exoskeleton of arthropods (cellulose, chitin, xylans).

cell recognition moities(glycolipids & glycoproteins) as important components of cell membranes, serving as probes through which the cell interacts with its environment.

Protective substances -some plant cell wall polysaccharides are elicitors of plant antibiotics (phtoalexins) E.g In soybean, fragments of pectic polysaccharide (-4-linked dodecagalacturonide) induces synthesis of a protein that inhibits insect & microbial proteinases.- Arabinoxylans have been postulated to inhibit ice formation, thus ensuring winter survival of cereals.

CLASSIFICATION OF CARBOHYDRATES

Monosaccharides: simple carbohydrates, cannot be hydrolyzed further into polyhydroxy aldehyde or ketone unit. Example- glucose, fructose, galactose.

Oligosaccharides: polymers made up of 2 to 10 monosaccharide units joined together by glycosidic linkages. Example- sucrose, lactose, raffinose.

Polysaccharides: polymers with hundreds or thousands of monosaccharide units. They are not sweet in taste ; therefore called non sugars. Are insoluble in water. Can be homopolysaccharides or heteropolysaccharides. Example- cellulose, glycogen, starch.

TYPES OF CARBOHYDRATES IN FOODThree main types : starch (complex carbohydrates) sugar fiber

On nutritional level total carbohydrate includes all three types, which is useful in carbohydrate counting.Counting can be done by either adding up grams of total carbohydrate or adding carbohydrate units .1 carbohydrate unit = 15 g of carbohydrate is a meal planning tool used in diabetes management to help optimize blood sugar level.

STARCH foods rich in starch include peas, potatoes, corn, dried beans, kidney beans, grains like oats, barley, rice. majority of grain products are made from wheat flour like pasta, bread, chapattis. Grain group includes -whole grain -refined grain Grain has three parts:Bran- outer hard shell of the grain, part that provides most fiber & most of the B vitamins & minerals.Germ- next layer, packed with nutrients & fatty acids along with vitamin E.Endosperm- soft part in the center of the grain which contains the starch.

Refined grain contains only endosperm.

SUGAR simple, fast acting carbohydrates. soluble in water. sweet in taste. monosaccharide and disaccharides. can be reducing or non-reducing. two types: - naturally occurring (those in milk & fruits) Example- fructose in fruits, lactose in milk.

-added sugars ( those added during processing of food) Example- saccharin, aspartame.

FIBER common in plant foods; absent in animal products like milk, eggs, meat, poultry etc. it is the indigestible part of plant foods ( fruits, vegetables, whole grains, nuts & legumes) Dietary fiber when consumed, mostly passes the intestines & is not digested. for good health, 25-30 gm of fiber intake per day is required in adults. sources include : -fruits & vegetables (apples, corn, berries) -whole grains, cereals, oats, bread. -nuts (peanuts, walnuts, almonds)

FLAVOUR & COLOUR PRODUCTION BY CARBOHYDRATESFlavor & color reactions of carbohydrate constituents of foods may be classified into:

Enzymatic browning reactionsCaramelizationMaillard reaction Strecker degradation

1.ENZYMATIC BROWNING REACTIONS

Part of natural process of decayWhen food substances are deprived of the protection of water, they get oxidized or chemically dehydrated to reactive intermediates, which polymerize to dull, brown, humic substances.Two types:Oxidative Browning:Oxidases are active & convert functional groups to reactive carbonyl compounds which undergo further non-enzymatic oxidative browning reactions.

Non-oxidative Browning:Glycosyl hydrolases initiate non-oxidative browning in natural products by the release of reducing sugars. It is important in color & flavor development in dates, honey, maple syrup, chocolate & vanilla processing. Reducing sugars undergo a series of reactions even in the absence of oxygen or other oxidants to yield reactive carbonyl compounds.

2.CARAMELIZATION

Involves a complex group of reactions that are the result of direct heating of carbohydrates.Heat hastens the inversion of sucrose to yield reducing sugars which condense to higher oligosaccharide & dextrins.When amino acids do not participate in the heat induced reactions, the complex color & flavor forming reactions of carbohydrates are called caramelization reactions.Brown pigments that characterize caramel & other foods are due to HMF & its precursors.Three commercial types of caramel colors:Acid fast caramel used in cola drinks, made using ammonium bisulphite catalyst.Brewers color found in beer, made form sucrose in the presence of ammonium ions.Bakers color in baked goods, results from direct pyrolysis of sucrose to give burnt sugar color.

3.MAILLARD REACTION

In the presence of amino compounds, the browning of sugars occurs more rapidly, particularly in neutral or alkaline conditions in a sequence of reactions called Maillard reaction.

Browning & aroma formation during cooking, frying, baking or roasting are caused by this reaction.

Lysine is the most reactive amino acid followed by met, arg, trp & his.

Chemical Mechanism: -Carbonyl group of sugar reacts with amino group of the amino acid producing N-substituted glycosylamine & water.-Unstable glycosylamine undergoes Amadori rearrangement, forming ketosamines.-Several ways for ketosamines to react further: (produce water & reductones) (diacetyl, aspirin, pyruvaldehyde & other short-chain hydrolytic fission products) (produce brown nitrogenous polymers & melanoidins)

4.STRECKER DEGRADATION

Involves transamination & decarboxylation reactions.

It is the interaction of -dicarbonyl compounds with -amino acids at elevated temperature.

The reaction yields aldehydes, aminoketones & CO2.

These aldehydes contribute to fruity, ester-like, malty green or honey like aromas in foods.

Aminoketones formed undergoes further reactions to yield pyrazine derivatives. These compounds together with products obtained from dimerization of sugar residues make a major contribution to the characteristic aroma of baking.

CARBOHYDRATE METABOLISMMetabolic pathways involved:Glycolysis the oxidation metabolism of glucose molecules to obtain ATP and pyruvate. Pyruvate from glycolysis enters the Krebs cycle, in aerobic organisms after moving through pyruvate dehydrogenase complex.

The pentose phosphate pathway, which acts in the conversion of hexoses into pentoses and in NADPH regeneration. NADPH is an essential antioxidant in cells which prevents oxidative damage and acts as precursor for production of many biomolecules.

Glycogenesis the conversion of excess glucose into glycogen as a cellular storage mechanism this prevents excessive osmotic pressure build up inside the cell.

Glycogenolysis the breakdown of glycogen into glucose, which provides a glucose supply for glucose dependent tissues.

Gluconeogenesis de novo synthesis of glucose molecules from simple organic compounds. An example in humans is the conversion of a few amino acids in cellular protein to glucose.

HARMS OF EXCESS CARBOHYDRATES

Excess consumption of carbohydrates causes pancreas to continue secreting insulin & body is constantly in fat storage mode. This leads to many health problems. Obesity excess fat storage. Insulin Resistance(Hyperinsulinemia) precursor to Type II Diabetes. High Blood Pressure - Excess insulin forces kidneys to retain Na ions, hence fluid retention increases. Blood retains more fluid hence Blood Pressure rises. High cholesterol Excess insulin causes LDL levels to rise. Heart disease When LDL particles migrate into the walls of coronary artery. Prostrate and Breast Cancer.

CARBOHYDRATE DEFICIENCYCaused by not taking a balanced diet. Acidosis shift from glycolysis to lipolysis & ketogenesis for energy needs. Acidity in blood & tissues rises & causes irreversible cell damage.

Ketosis Prolonged fasting or starvation; Acetyl CoA in liver is used to produce ketone bodies which leads to ketosis.

Hypoglycemia Non availability of glucose ; occurs when blood glucose levels drop under 70 mg/ml. Symptoms include giddiness, fatigue, distress.

Constipation Dietary fiber is an essential component of carbohydrate food. It helps digestion & prevents recto-colon cancer.

Mood swing - Dietary carbohydrate exclusion causes the brain to stop regulating serotonin hormone. Low serotonin supply causes mood swing and depression.

REFERENCESFood Processing and Preservation by B. SivasankarFood Science and Technology edited by Geoffrey Campbell-Platthttp://allnutriments.blogspot.in/2013/03/carbohydrate-deficiency-diseases.htmlhttp://www.diabetes.org/food-and-fitness/food/what-can-i-eat/understanding-carbohydrates/types-of-carbohydrates.htmlhttp://www.humfeldchiropractic.com/the-dangers-of-excess-carbs/http://www.nadyapeche.com/refined-grains-health-risks/https://en.wikipedia.org/wiki/Carbohydrate_countinghttps://en.wikipedia.org/wiki/Maillard_reactionhttps://en.wikipedia.org/wiki/Carbohydrate_metabolism

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