1. Water
Water content is very influential on the quality of food because it can affect the appearance, texture, and taste of our food. Even dry foods, such as dried fruit, flour, and seeds, contain a certain amount of water. Water plays a role in food substances and metabolic wastes, as a reaction medium that stabilizes the formation of biopolymers, and so on.
All foodstuffs contain water in varying amounts, be it animal or plant foods. For example, fresh vegetables and fruits have 90-95% water content, 85-90% milk, 70-80% fish, 70-75% eggs, and 60-70% meat.
Reduction of water, in addition, aims to preserve it as well as to reduce the volume and weight of food so as to facilitate and save packing. Some types of grain traded in the market have a certain moisture content, for example, rice with a moisture content of about 14% or soybeans with a moisture content of about 8%. At this water content, rice and soybeans have a longer shelf life and shelf life compared to their fresh state at a higher water content.
Water in food is found in the form of free water and bound water. Free water is easily removed by evaporation or drying, while bound water is very difficult to remove from food even by evaporation.
2. Carbohydrates
Carbohydrates are the main source of calories for humans. As much as 60-80% of calories obtained by the human body come from carbohydrates. This is especially true for the nations of Southeast Asia. Besides being the main source, it also has an important role in determining the characteristics of food ingredients, such as taste, color, texture, and others. For the human body, most carbohydrates are obtained from daily food ingredients, mainly from plants (plants). The formation of carbohydrates from plants through the process of assimilation or photosynthesis, which occurs through the leaf surface that sucks air (CO2), along with water absorbed by the roots, is carried to the leaf tissue.
Chlorophyll is a green dye (pigment) that absorbs energy from the sun and causes plants to form carbohydrates from CO2 and water. Carbohydrates (starch) will be transported to storage places, namely in fruits, roots, and tubers.
According to the size of the molecule, carbohydrates can be grouped into three groups, namely:
a. Monosaccharides, which are carbohydrates with the simplest molecular structure, consisting of 5 or 6 C atoms. Included in this group are carbohydrates found in plants and fruits that taste sweet.
b. Oligosaccharides, are polymers of 2 to 10 monosaccharides, which are usually found in sugarcane or beet juice.
c. Polysaccharides are polymers consisting of more than 10 monosaccharide monomers. Usually found in plant starches such as cereals and tubers.
a. Monosaccharides
Monosaccharides are the final product of the complete breakdown of the most complex carbohydrates in the digestive process. In the human body, monosaccharides are directly absorbed by the walls of the small intestine, then enter the bloodstream. The important monosaccharides are glucose, fructose, and galactose.
Glucose, also known as dextrose, is found in many fruits and vegetables. All carbohydrates in the body will eventually be converted into glucose. Fructose or levulose is found with glucose in fruits and vegetables, especially honey. Galactose has only been found to come from the breakdown of disaccharides.
b. Oligosaccharides
Oligosaccharides are polymers with polymerization degrees of 2 to 10 and are usually water-soluble. Oligosaccharides consisting of two monosaccharide molecules are called disaccharides, and if they consist of three monosaccharide molecules, they are called trioses.
There are three important disaccharides, namely sucrose, maltose, and lactose. The digestion of sucrose (sucrose or cane sugar) will be broken down into glucose and fructose. Maltose is found as an intermediate product of the decomposition of starch. Maltose will be broken down into two glucose molecules. Lactose is abundant in milk, in the body it will be broken down into glucose and galactose.
c. Polysaccharide
Polysaccharides are a group of carbohydrates that have a more complex molecule, consisting of many monosaccharide molecules. Polysaccharides in foodstuffs function as texture reinforcements (cellulose, hemicellulose, pectin, and lignin) and as energy sources (starch, dextrin, glycogen, and fructans). This texture-strengthening polysaccharide cannot be digested by the body but is a dietary fiber that can stimulate digestive enzymes.
Polysaccharides are polymers of monosaccharide molecules that can be straight or branched and can be hydrolyzed with specific enzymes that work. The results of hydrolysis will produce oligosaccharides and can be used to determine the molecular structure of polysaccharides. Some of the important polysaccharides are starch, glycogen, and cellulose.
1) Starch
Starch is a very important source of energy because most carbohydrates are in the form of starch. Dextrin is an intermediate in the breakdown of starch. The molecule is simpler when compared to flour molecules and is easily soluble in water, easy to digest so it is good for baby food. Starch is also the main food reserve in plants, is actually a mixture of two polysaccharides namely amylose and amylopectin.
The two fractions can be separated with hot water. The soluble fraction is called amylose and the insoluble fraction is called amylopectin. The number of amylose molecules is about 20% of the total starch, consisting of 70 to 350 glucose units linked together to form straight chains. The amylopectin molecule consists of up to 100,000 glucose units linked together to form a branched-chain structure.
Various kinds of starch are not the same in nature depending on the length of the C chain, as well as whether the molecular chain is straight or branched. The role of the ratio of amylose and amylopectin is seen in cereals, for example in rice. The smaller the amylose content or the higher the amylopectin content, the more sticky the rice will be
2) Glycogen
Glycogen is a carbohydrate reserve in the body that is stored in the liver and muscles, is an "animal starch", is soluble in water (vegetable starch is not soluble in water). When it reacts with iodine it will produce a red color.
Glycogen is a polymer whose molecular structure is almost the same as that of amylopectin. Glycogen has many branches (20-30 branches) that are short and tight, while amylopectin has only about 6 branches. Glycogen has a molecular weight (BM) of about 5 million and is the largest molecule in nature that is soluble in water. The number of glycogen reserves are very limited, when needed by the body, it is converted back into glucose.
3) Cellulose
Cellulose is another polysaccharide consisting of long chains of glucose units. The basic structure is similar to starch but the glucose units are bonded in a different way. Humans do not have enzymes capable of breaking this bond and therefore, humans cannot use cellulose as food, but it is useful in the mechanism of the digestive system.
Cows and other ruminant animals can break down and use cellulose as an energy source because they have bacteria that can break down cellulose in their rumen (the first of the four stomach parts of cows). This explains why cows can use grass and dry forage as food while humans cannot.
Cellulose is a long fiber that together with hemicellulose, pectin, and protein, forms a network structure that strengthens plant cell walls. In the process of ripening, storage, or processing, the cellulose components undergo changes so that there is a change in texture.
The long cellulose bonds can form the volume of food, causing a feeling of fullness, and condense the remnants of nutrients that are no longer absorbed by the intestinal wall. The properties of cellulose are as follows: give shape or structure to plants, are insoluble in cold or hot water, cannot be digested by human digestive juices so that they cannot produce energy but are useful in the mechanism of digestive organs, can be broken down into glucose or certain enzymes.
The cellulose derivative known as carboxymethyl cellulose (CMC) is often used in the food industry to get a good texture. For example, in the manufacture of ice cream, the use of CMC will improve the texture and the lactose crystals formed will be smoother. CMC is also often used in foodstuffs to prevent retrogradation.
4) Hemicellulose
If the components that makeup plant tissue are analyzed and separated, the lignin will be separated at first and the remaining compound is holocellulose. Furthermore, it turns out that holocellulose consists of cellulose and other compounds that are soluble in alkali. From the results of the hydrolysis of hemicellulose, it is estimated that the monomer units that form it are not the same. The main building blocks of cellulose are D-xylose, pentose, and other hexoses.
The difference between hemicellulose and cellulose is that hemicellulose has a low degree of polymerization and is easily soluble in alkali but difficult to dissolve in acid, while cellulose is the opposite. Hemicellulose is not long fiber-like cellulose, nor is the combustion temperature as high as cellulose. The result of hydrolysis of cellulose will produce D-glucose, while hemicellulose will mainly produce D-xylose and other monosaccharides.
One of the easy and inexpensive analytical methods to estimate the carbohydrate content in foodstuffs is by means of a rough calculation (proximate analysis) or also called carbohydrate by the difference in the following way.
% carbohydrates = 100% - % (protein + fat + ash + water)
3. Protein
Protein is one of the most important food substances for
survival of a creature. In addition to functioning as fuel in the body, it also functions as a building block and regulator. Protein is a source of amino acids that contain elements C, H, O, and N which are not owned by fat or carbohydrates. Protein molecules also contain sulfur (S) and phosphorus (P) and there are also types of proteins that contain metal elements such as iron and copper.
In every living cell, protein is a very important part. In most body tissues, protein is the largest component after water, with a weight of approximately 50 percent of the dry weight of cells in tissues such as liver and meat, while in fresh textiles it is about 20%.
Basically, proteins are formed by amino acid units that form "polymers" so that they are long compounds. Amino acid molecules have an amino group (-NH2,) which is basic, and a carboxyl group (-COOH) which is acidic. This situation allows amino acids to react both with acids and bases, as well as other reagents. The amino group of an amino acid can react with the carboxyl group of another amino acid by removing one molecule of H2O and forming a peptide bond (-CO-NH-). The two amino acid molecules that form a peptide bond are called dipeptides. The free amino and carboxyl groups of the dipeptide can react again with other amino acids to form polypeptides,
The value of protein quality depends on the amino acids it contains, which are the smallest part of protein substances.
Amino acids are divided into essential and non-essential amino acids. Essential amino acids are amino acids that are needed by the body but cannot be synthesized by the body, so they must be found in the daily diet. Non-essential amino acids are amino acids that can be formed in the body, so they do not absolutely have to be found in food. Essential amino acids, including leucine, isoleucine, lysine, tryptophan, phenylalanine, methionine, threonine, and valine. Non-essential amino acids include arginine, cysteine, glycine, histidine, serine, and tyrosine.
Arginine is not essential for children nor for adults but can improve the growth of infants, while histidine is essential for children but not essential for adults.
The functions of proteins include: forming body tissues, replacing cells that have been damaged and worn out, making milk, enzymes, and hormones, making blood proteins, maintaining the acid and alkaline balance of body fluids and blood vessels, and providing energy.
Protein also functions as a calorie provider, if the amount of carbohydrates and fat is not sufficient for the body's needs. If the protein does not contain enough essential amino acids, so it cannot be used to build body tissues, the protein can be oxidized to produce energy.
Based on the source of protein can be divided into two parts, namely: animal protein derived from animals such as milk, fish, meat, eggs, cheese, liver, and so on.
Vegetable protein derived from plants is found in nuts such as soybeans, peanuts, and their processed products (eg tofu and tempeh), green beans, kidney beans, and so on. Animal protein is of higher value than vegetable protein because animal protein is more complete in its essential amino acid content and its composition is close to the protein value of the human body, while vegetable protein is of lower value, except for protein from nuts and their processed products.
4. Fats and Oils
Fat molecules consist of the elements carbon, hydrogen, and oxygen (C, H, and ).
O). Besides carbohydrates, fat is the second source of energy for the human body. One gram of fat produces 9 calories so that as a source of calories it is actually more beneficial, it also dissolves vitamins A, D, E, K so that it can be absorbed by the walls of the small intestine, and provides essential fatty acids. Essential fatty acids cannot be made by the human body, must be taken from food, and serve to protect the body's delicate organs. Fat energy means greater than carbohydrate (4 calories) and protein (4 calories) molecules. Fats give food a savory and smooth taste and can keep you full for longer. Based on its shape, some fats are in solid form and some are in liquid form.
Liquid fats are easier to digest than solid fats. There are also fats that when heated just a little already melt, such as butter.
Based on the source, fat is divided into 2 (two) groups, namely:
a. fats derived from plants such as coconut oil, peanut oil, corn oil, margarine, and so on;
b. fat derived from animals such as beef fat, goat fat, lard, butter, fish oil, and so on.
Based on their chemical bonds, fats are divided into 2 (two) groups:
a. fatty glycerides consisting solely of fatty acids and glycerol;
b. substances that in addition to containing fatty acids and glycerol also contain other substances such as phosphorus, glycogen, and so on.
Pure fat will be broken down into fatty acids and glycerol by the presence of enzymes in the body. Pure fats must be present in the diet for various reasons, among others, to dissolve various vitamins and to obtain certain types of essential fatty acids. Essential fatty acids cannot be made by the body, must be taken from food, and serve to protect the body's delicate organs. Some examples of essential fatty acids, namely oleic acid, linoleic acid, linolenic acid, and arachidonic acid are mainly found in plant fats. Non-essential fatty acids include butyric acid, palmitic acid, caproic acid, and so on.
Substances that contain fat for example fat bond with phosphorus salts called phospholipids, fat bonds with glycogen called glycolipids, fat bonds with chromatin called chromolipids, and steroids.
The fat content in each food is different. In the food industry, fat is often added for a specific purpose. The function of fat in food processing is as a heat-conducting medium (cooking oil, shortening or white butter, lard fat, butter, and margarine) besides the addition of fat is intended to add calories, improve the texture and taste of foodstuffs (eg confectionery), dissolve vitamins A, D, E, K so that it can be absorbed by the walls of the small intestine, and provide essential fatty acids.
The average human needs 34 -1 gram of fat per kilogram of weight body. Almost 20 - 25% of daily caloric needs are obtained from fat. In countries with cold climates, everyone's need for fat is more This is because fat provides higher calories so that it can protect the body from the cold climate around it.
Animal fats contain quite a lot of sterols called cholesterol, while vegetable fats contain phytosterols and contain more unsaturated fatty acids, so they are generally in liquid form. Animal fat in solid form (fat) usually comes from land animal fats such as milk fat, lard, beef fat. Marine animal fats for example whale oil, cod liver oil, herring oil, while liquid vegetable fats are divided into 3 groups, namely:
a. drying oil which will form a hard layer when it dries in the air (paint oil);
b. semi-drying oil (corn oil, cottonseed, sunflower);
c. non-drying oil (coconut oil and peanut oil).
Vegetable fats that are in solid form are cocoa oil and palm kernel oil. People who eat fat more than they need move the body less, then the fat is stored in the body as a reserve, causing people to become fat.
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