Presentation on theme: "CARBOHYDRATES a)The chemical name, nature and basic characteristics of the following carbohydrates. Students do not need to know the chemical structures."— Presentation transcript:
CARBOHYDRATES a)The chemical name, nature and basic characteristics of the following carbohydrates. Students do not need to know the chemical structures and complex formulae. Sugars monosaccharides glucose fructose disaccharides maltose sucrose lactose. Reducing sugars. Simple polysaccharides starch amylose amylopectin glycogen cellulose
Complex polysaccharides xanthan alginate carrageen guar pectins Fibre Carbohydrates in the diet. b) Fundamental working properties of carbohydrates: sweetening: comparison of the sweetness level of sugars compared with sucrose thickening/gelatinisation importance of hydrogen bonding in gelatinisation retrogradation and syneresis stabilising use of cellulose and gums in stabilising food products browning reactions caramelisation Maillard reaction
THE COMPOSITION OF CARBOHYDRATES Macronutrients Made up of carbon, hydrogen and oxygen 3 main types – sugar, starch and fibre Photosynthesis produces carbohydrates which are found in all plant foods
DIETARY FUNCTIONS OF CARBOHYDRATES Provide energy (sugar & starch) Aids digestion (fibre) Sweetens and flavours food (sugar) Adds bulk to your diet (starch & fibre) Helps to lower blood cholesterol (fibre)
WHAT IS CHOLESTEROL? Cholesterol, a waxy substance produced by the liver and found in certain foods, is needed to make vitamin D and some hormones, build cell walls, and create bile salts that help you digest fat. Your liver produces about 1,000 milligrams of cholesterol a day, which is enough cholesterol for your body’s needs. Too much cholesterol in the body can lead to serious problems like heart disease. It's hard to avoid cholesterol entirely because so many foods contain it.
GOOD VS BAD CHOLESTEROL LDL (low density lipoproteins) cholesterol is known as "bad cholesterol" HDL (high density lipoproteins) cholesterol is "good cholesterol" Most cholesterol is LDL cholesterol, and this is the kind that's most likely to clog the blood vessels, keeping blood from flowing through the body the way it should. HDL cholesterol removes cholesterol from the blood vessels and carries it back to the liver, where it can be processed and sent out of the body
GOOD VS BAD CHOLESTEROL When LDL cholesterol levels are high, cholesterol is deposited on the walls of arteries and forms a hard substance called plaque. Over time, plaque causes the arteries to become narrower, decreasing blood flow. When this affects the blood vessels that supply the muscles of the heart it puts a person at risk of having a heart attack. When it affects the blood vessels that supply the brain it puts a person at risk of having a stroke. Cholesterol may also block blood flow to other vital organs, including the kidneys and intestines. This is why it's so important to start paying attention to cholesterol levels as a teen — you can delay or prevent serious health problems in the future
SUGARS INTRINSIC sugars are found naturally in the cells of fruit and vegetables EXTRINSIC sugars include granulated, caster, Demerara, icing, treacle, syrup and are added to cakes, biscuits, sweets, desserts, sauces, soft drinks and soups. Diets high in extrinsic sugar can lead to tooth decay and obesity. Sugar provides “empty” calories as it contains no other nutrients at all.
Simple Carbohydrates or Sugars Sugary carbohydrates can quickly and easily be broken down and converted into energy very soon after they have been consumed. But that makes your blood sugar levels rise rapidly, giving a boost of energy, but it is quickly followed by a sharp drop of blood sugar levels and therefore a drop in energy levels, which can ultimately leave us feeling more tired than in the first place. Sucrose is the sugar we use to sweeten our hot beverages and it’s present in cakes, pastries, soft drinks and sweets. It is also found in other processed foods, which we may not be aware of. This type of sugar, the unnatural kind, causes tooth decay, mood swings, hunger and lack of concentration. However, the natural sugars found in fruit and milk release energy slowly, contain lower levels of sugar and do not contribute to weight gain. They are also high in fibre and vitamins. Table sugar (sucrose) is made from sugar beet or sugar cane. The beet or cane is collected, crushed and then mixed with water. The liquid is then boiled and sugar crystals are formed.
SUGAR DOES NOT CAUSE DIABETES A very common misunderstanding is that sugar causes diabetes. If you have diabetes, you do need to watch your sugar and carbohydrate intake to properly manage your blood sugar level. However, if you do not have diabetes, sugar intake will not cause you to develop the disease. The main risk factors for Type 2 diabetes are a diet high in calories, being overweight, and an inactive lifestyle. BROWN SUGAR IS NOT BETTER FOR YOU THAN WHITE SUGAR The brown sugar sold at grocery stores is actually white granulated sugar with added molasses. Brown sugar contains minute amounts of minerals. But unless you eat a gigantic portion of brown sugar every day, the mineral content difference between brown sugar and white sugar is absolutely insignificant.
STARCH Starch is found in cereals (wheat, barley, rice, oats, maize and rye) bread, potatoes, pasta and root vegetables They are filling and provide you with many other nutrients: for example, cereals contain the Vitamin B complex
Starchy Carbohydrates Starchy carbohydrates can be found in most grains, cereals, potatoes, brown rice, bread, pasta and certain fruits and vegetables. They are basically many sugar molecules joined together in a chain. Due to the more complex chemical structure, starchy carbohydrates are not broken down or digested as quickly or easily as sugary carbohydrates. This is much better for the body, as there are no surges in blood sugar levels and the energy provided from these foods is released at a slow and steady rate, meaning that energy levels should stay more or less the same all day. Complex carbohydrate foods are often lower in fat than simple carbohydrate foods and also contain plenty of vitamins and fibre, which are essential nutrients for the body.
White or refined carbohydrate has undergone a process to remove the bran from the grain. A typical example is bread. White bread has had the bran (the fibre) and germ removed.. It is the same with white pasta, white rice and sugary cereals. Many people prefer refined carbohydrates for their taste and texture, however; they have essentially had most of the goodness and natural fibre removed from them. But they are still better for you than sugary carbs. Unrefined carbohydrates such as wholemeal bread, wholegrain cereals and wholemeal pasta are generally heavier in texture, more filling, more natural, they contain more fibre, vitamins and minerals, leave you feeling fuller for longer, and are definitely healthier for you. It is always a better choice if you are trying to lose weight or trying to be healthy to choose unrefined carbohydrates as opposed to refined carbohydrates. What is the difference between white and brown carbohydrates?
NON-SUGARS (not sweet) SIMPLE POLYSACCHARIDES STARCH Root vegetables Seeds Unripe fruit Rice Potatoes Cereals CELLULOSE/FIBRE/NSP Skins of fruit & vegetables Bran Wholegrain cereal products
NON-SUGARS (not sweet) COMPLEX POLYSACCHARIDES PECTIN Orchard fruits Berries used in jam, gels and jellies Citrus Fruits Seaweed Carrageenan GUMS Used as thickeners, stabilisers and emulsifiers
FIBRE Fibre (or non-starch polysaccharides – NSP) is the cellulose found in the outer skins and flesh of fruit and vegetables Fibre can be split into 2 different groups
SOLUBLE FIBRE Found in the flesh of fruit and vegetables, oats, beans and lentils. Digestion partially breaks it down to form a gel-like substance that coats the digestive tract. This helps to speed up digestion, helping to lower blood cholesterol levels and prevent cancer and other digestive problems.
INSOLUBLE FIBRE Found in the outer skins of fruit and vegetables, cereals and wholegrain food products. The body cannot digest insoluble fibre. It acts as a bulking agent, absorbing the end-products of digestion to allow waste products to be removed from the body
FIBRE Too little fibre (soluble or insoluble) in your diet can lead to digestive problems such as: constipation diverticular disease (inflammation of the digestive tract) appendicitis haemorrhoids.
REDUCING SUGARS Sugars which contain a potential aldehyde group, for instance glucose, maltose and lactose. Some sugars such as fructose contain a ketone group but are still reducing sugars. Tests for by their ability to break down Fehling’s solution. How are they used in the food industry ? Anyone who can find out will win a prize!
THE MAILLARD REACTION http://www.5min.com/Video/Learn-about- the-Maillard-Reaction-83227082