Nutrients and Their Functions

Nutrient : A substance essential for the growth, maintenance, function and reproduction of a cell or organism. OR The essential substances contributed by food are called nutrients.

There are several categories of nutrients, includes carbohydrates, proteins, fats, vitamins, minerals and fibre. 

• The nutrients are classified into two categories: 

Macronutrients: Are those which the body requires in relatively large amounts. The requirement of these nutrients are in grams. Ex: Carbohydrates, fats and proteins. 

Micronutrients: Are required in much smaller quantities by the body. The requirement of these nutrients in milligrams and micrograms. Ex: Vitamins and minerals.

• Functions of Nutrients

Generally three major functions are performed by nutrients. These are,  

1. Supplying energy 
2. Building body tissues
3. Protecting the body from infection and regulating body processes

Each nutrient class has its own function. The nutrients found in foods are carbohydrates, proteins, fats, minerals, vitamins and water. Fabre is also an essential component of our diet. 

Carbohydrates: 

Starch found in cereals and sugar in sugarcane and fruits are examples of carbohydrates in foods.  The main function of carbohydrates is to provide energy needed by our body.  Those not used immediately for this purpose are stored as glycogen or converted to fat and stored and to be utilized for energy supply when needed. 

One gram of carbohydrate provides about 4 kilocalories (4 Kcal). Energy is measured in kilocalories.  One kilocalorie is the amount of heat required to raise the temperature of one kilogram of water by one degree centigrade.

Fats: 

Oils found in seeds, butter from milk and lard from meat, are examples of fats found in foods. Fats provide more than double the energy supplied by carbohydrates, 9 Kcal per gram. This makes them concentrated sources of energy. Foods rich in fat provide satiety and are more palatable. Fat which is not used by the body is stored by a specific tissue called adipose tissue. Adipose tissue is present under the skin and around vital organs and prevent excessive heat loss and keep the body warm.
One of the major functions of the fats is as sources of essential fatty acids. The unsaturated fatty acid cannot be synthesized by the body. The essential fatty acids called linoleic and linolenic acids. Fats are also important as a vehicle for carrying fat-soluble vitamins and also aid in their absorption.

Proteins: 

Casein from milk, albumin in egg, globulins in legumes and gluten in wheat are examples of proteins occurring in foods. About 10 per cent of the total energy is supplied by proteins in the diet. It provide 4 kilocalories/ gram. Protein taken in excess is converted to carbohydrates and fats and is stored in the body. The main function of protein is the building of new tissues and maintaining and repair of those already built. Synthesis of regulatory and protective substances such as enzymes, hormones and antibodies is also a function of food proteins. Protein also fulfil requirement of essential amino acid of human body. Examples are Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine. (Histidine And alanine essential only for  infants only).

Vitamins: These are needed for growth, normal function and processes of the body.

a) The water soluble vitamins:

Folic acid and vitamin B12 are important in formation of normal red blood cells in the bone marrow. The proper functioning of the digestive tract and nervous system also requires sufficient intake of vitamin B12 and B6 Vitamin C is another water-soluble vitamin. Its major functions include its role in collagen formation. Collagen is a protein and it forms a part of connective tissues. Proper synthesis of collagen helps wound healing. B-complex vitamins play a crucial role in the metabolism of carbohydrates, fats and proteins. Vitamins such as thiamin, riboflavin, niacin and folic acid are referred as coenzymes. 

Food Preservatives

 Food Preservatives

Preservatives: substances which when added to food retard, inhibit or arrest the activity of microorganisms.

q  From prehistoric times humans have attempted to preserve food products from the Decay effects of microorganisms. Some food preservatives like salt, nitrites and Sulphite have been in use for many years.

q  Even though newer packaging techniques, processing and storage methods are able to preserve foods without chemical preservatives.

q  Even today these chemicals play a significant role in protecting the food supply mainly because preservation using chemical preservatives is cheaper and more convenient.

Classification of Food Preservatives

Preservatives are classified into two classes, Class I and Class II preservatives.

1. Class I Preservatives

q  Class I preservatives are also called as natural preservatives. They are common salt, sugar, dextrose (glucose), spices, vinegar or acetic acid, honey, and vegetable oils.

q  There is no restriction to the addition of Class I preservatives to any food.

  

2. Class II Preservatives

q  Class II preservatives are also called as Synthetic or Artificial preservatives. Use of more than one Class II preservative in a food is prohibited unless specified under the Rules.

q  The use of Class II preservatives is restricted to only certain foods and the amount of the preservative which can be added to these foods is also specified under the FSS Rules. The presence of a Class II preservative in any food has to be declared on the packaging of the food.

q  It includes Benzoic acid, sulphurous acids, nitrates or nitrites, sorbic acid, potassium and calcium salts, calcium or sodium propionates, lactic acid, sodium or calcium propionate, methyl or propyl parahydroxy benzoic acid, sodium diacetate and sodium potassium and calcium lactate and Nisin.

Class I Preservatives

Salt (sodium chloride):

q  Salt has been used as a preservative since the beginning of recorded history. Pickling of fruits and vegetables and salting of fish and meat are widely practiced.

q  The antimicrobial activity of sodium chloride is essentially related to its ability to reduce water activity (aw) and create unfavorable conditions for microbial growth. As the water activity of the external medium is reduced, microbial cells are subjected to osmotic shock and rapidly lose water through plasmolysis. These results in cells die or remain dormant.

q  Other possible mechanisms include limiting oxygen solubility in the medium and toxicity of chloride ions.

q  The inhibitory effect of sodium chloride is dependent on several factors particularly pH. As acidity increases, less sodium chloride is required to inhibit microbial growth.

q  Sodium chloride intolerant bacteria are inhibited by concentrations as low as 1%. Some bacteria like the lactic acid bacteria used in producing lactic fermented vegetables can tolerate from 6–15 % sodium chloride.

q  In general, food borne pathogenic bacteria are inhibited by a water activity of 0.92 or less which is equivalent to sodium chloride concentration of 13%. That’s why for salt curing, sodium chloride concentration of about 13% is commonly used. 

Acetic acid:

q  Synthetic vinegar (dilute acetic acid) and brewed vinegar are widely used as acidulants and antimicrobials. Use of Vinegar in pickles are common in our country.

q  Acetic acid is more effective against yeasts and bacteria than molds. Acetic acid is also more effective at lower pH. Generally, 1-2 % acetic acid is sufficient to inhibit most of the organisms.

Sugar and spices:

q  The main function of sugar is to reduce the water activity of the medium thus inhibiting the growth of microorganisms.

q  Many chemical substances in spices (terpenes) have been shown to have antimicrobial properties.

Class II Preservatives

Benzoic acid and benzoates:

q  Benzoic acid is found naturally in cranberries, plums, prunes, cinnamon, cloves and most berries. It is a strong antimycotic agent. Most yeasts and molds can be controlled using 0.05–0.1% benzoic acid. Control of many bacteria requires much higher concentration.

q  Benzoates are most effective at low pH (pH 2.5–4.0). Benzoic acid is permitted in several products like squashes, syrups, crushes, fruit juices, jams, jellies, marmalade, beverages, pickles and tomato products. Benzoic acid and its sodium and potassium salts have been generally recognized as safe (GRAS).

Sulphur dioxide and Sulphites:

q  Sulphur dioxide and its various salts have a long history of use dating back to the times of the ancient Greeks. They have been used extensively as antimicrobials and to prevent enzymatic and non-enzymatic browning in a variety of food products.

q  Sulphur dioxide is a colorless, nonflammable gas with a suffocating odor. It dissolves readily in water to produce sulphurous acid (H2SO3). Sulphur dioxide and sulphites are permitted for a number of products like fruit pulps, squashes, syrups, crushes, cordials, wines, RTS beverages, and dehydrated fruits and vegetables.

q  Sulphur dioxide is also used as an anti-browning agent. Fruits are exposed to fumes of burning Sulphur before drying to prevent browning and also insect and microbial attack. Sulphite solutions are also used as dip solution for vegetables before drying or dehydration.

q  Sulphur dioxide and several sulphites have GRAS status. Sulphites cannot be used in meats and in foods that are sources of the vitamin thiamine. As sulphites have strong bleaching action on plant pigments like anthocyanins, they should not be used for preserving such products.

Sorbic acid and sorbates:

q  Sorbic acid and its sodium, potassium and calcium salts are collectively known as sorbates. Sorbic acid is present in some berries like berries of the mountain ash berry (rowanberry). Sorbates inhibit most of the species of yeasts and molds. Several species of bacteria are also inhibited by sorbates.

q  Sorbates are permitted for only a few fruit and vegetable products. They include jams, jellies, marmalades, glazed or candied fruits, fruit bars, fruit juice concentrates and prunes. Some of the other products include cheese, flour confectionary, smoked fish, preserved chapattis and fat spreads. Sorbic acid and potassium sorbate have GRAS status.

Nitrites:

q  Nitrites have been used in meat curing for many centuries. For meat curing, nitrite is used along with a mixture of salt, sugar, spices, and ascorbate. Nitrite contributes to the development of the characteristic color, flavor, and texture improvement and preservative effects.

q  Nitrites are white or pale-yellow hygroscopic crystals. Sodium nitrite is quite soluble in water. Nitrite has a strong inhibitory action against Clostridium botulinum and several other microorganisms. It is more effective below neutral pH (below 7.0). 

Antibiotics:  Biologically derived antimicrobials:

These substances are allowed for food use only in recent years. Nisin and Natamycin have been permitted in some foods.

Nisin

q  It is a polypeptide produced by Steptrococcus lactis (now called lactococcus lactis). Nisin has a narrow spectrum affecting only gram-positive bacteria, and it generally does not inhibit gram-negative bacteria, yeasts or moulds.

q  The antimicrobial action of nisin is pH dependent, it increases as the pH decreases. It is effective at very low concentrations i.e. 0.04-2.0 ppm. Nisin has been permitted in packaged coconut water and canned rasagolla.

Natamycin:

q  It is produced by the bacterium Streptomyces natalensis. Natamycin is primarily effective against yeast and moulds and is ineffective against bacteria, viruses and actinomyces. Natamycin is also effective at very low concentrations i.e. 5-10 ppm. Natamycin has been permitted for surface treatment of hard cheese

 

 

Eco-friendly Packaging:Today's Need

     Usage of non-biodegradable materials for the various packaging applications has raised environmental pollution concerns. Food packaging accounts for the biggest growing sector within the synthetic plastic packaging market domain. Large amounts of different materials, like paper, glass and plastics, are used globally to manufacture packaging materials and more than two thirds are used in the food sector alone. This amount is growing unceasingly as a result of changes occurring in habits of food preparation and consumption, as well as the positive development of various areas and markets in the world. The packaging industry consumes the highest volumes of plastics produced globally and is the main source supplying waste plastics into the environment at an alarming rate. This can be attributed to single use plastics and the increase of on the go snacks and readymade meals that imply the once-off use of durable plastic packaging material. As a result, there is increasing need for eco-friendly sustainable packaging materials with the desired physical, mechanical and barrier properties for food packaging.

 

  

Biodegradable Food Packaging

The food packaging industry is now in pursuit of biodegradable packaging that is lightweight  for reducing materials use, waste and as well as transportation costs. Plastics from biopolymers are promising to fulfill this requirement. Biodegradation is a process of defragmentation, initiated by heat, moisture, and/or microbial enzymes, which transforms larger molecular substances into smaller compounds. It can also be simply defined as a process by which substances are broken down by living organisms. 

Due to the increasing environmental concerns created by excessive plastic accumulation, interest has shifted towards the development of such packaging materials that not only improve performance but are also easy to recycle and reuse i.e., “bio-plastics”.  According to the European Bioplastics organization, bioplastics can be defined as plastics based on renewable resources or as plastics which are biodegradable and/or compostable polymers. Bioplastics are derived from different renewable sources such as vegetable oil, corn starch, potato starch, fibers obtained from pineapple, jute, hemp, henequen leaves and banana stems and also from used plastic bottles and other containers using microorganisms.

 

Natural polymers or polymers derived from biomass

The natural polymers are derived from animal, marine, and agricultural sources, which include the polysaccharides, such as starch, cellulose, chitosan, gums etc., proteins like plant derived proteins (zein, gluten, soy, etc.) and animal extracted proteins (casein, collagen, gelatin, etc.) and lipids including cross linked triglycerides. By nature most of these polymers are hydrophilic and crystalline in nature, which create several problems while processing in moist food packaging. However they have excellent gas barrier properties which make them acceptable for their utilization in food packaging.

a)       Starch: Starch is the most abundant commonly used renewable raw material and easy biodegradable natural resource. It is obtained from seeds, corn, wheat, rice, potato, sweet potato, and cassava. Starch is usually used as a thermoplastic and constitutes a substitute for polystyrene (PS). It is plasticized through destructuration in presence of specific amounts of water or plasticizers (glycerol, sorbitol) and heat and then it is extruded. Starch is an attractive material for packaging applications because of its relatively low cost, availability, and biodegradability. Starch having poor resistance to moisture and their poor mechanical property restricts their use. Therefore to improve these properties starch is blended with various biopolymers and certain additives.

b)      Cellulose: Cellulose is the most abundant natural polymer and is derived by a delignification from wood pulp or cotton linters. Cellulose is very difficult to use in packaging because it is hydrophilic and crystalline in nature possessing poor mechanical properties in its raw form. Therefore, it must be treated with chemicals like NaOH, H2SO4, CS2, etc. to produce cellophane having excellent mechanical characteristics. Cellulose derivatives can be produced by derivatization of cellulose from the solvated state, via esterification or etherification of hydroxyl group. Cellulose derivative forms are used for films or edible coatings are Hydroxypropyl cellulose, hydroxypropyl methylcellulose, Carboxymethyl cellulose or Methyl cellulose.  Incorporation of hydrophobic compounds is one method for increasing the moisture barrier, such as fatty acids into the cellulose ether matrix to develop a composite film.

c)       Chitosan or chitin: Chitosan or chitin, is the second abundant polysaccharides resource after cellulose found in nature. It naturally appears in the exoskeleton of arthropods and in the cell walls of yeasts and fungi. It is produced commercially by chemical extraction processes from prawns and crabs wastes. Chitosan is obtained from deacetylation of chitin, and different factors (e.g. alkali concentration, incubation time, and chitin to alkali ratio, temperature and chitin source) can affect its properties. Chitosan forms films without the addition of additives, exhibits good carbon dioxide and oxygen permeability, as well as excellent mechanical properties and antimicrobial properties which reduces the oxidation process and is beneficial for increasing the shelf life and quality of food products.

d)      Proteins: Proteins are complex structures made up of amino acids and can be obtained from plant (wheat gluten, corn, zein, soy protein etc.) and animal (casein, whey, keratin, gelatin, etc.) sources. They are highly desirable to modify the required characteristics of packaging materials due to the presence of unique side chain in their structure. Due to the renewable nature, biodegradability and their excellent gas barrier properties proteins and protein based materials find their use in many industrial applications. But they are adversely affected by their hydrophilic nature like starch-based polymers. Therefore, they need to be blended with other polymers or must be chemically or micro-biologically modified.

i.         Casein is a milk derived protein, when processed with suitable plasticizers at temperature of 80-100 ⁰C, form materials with mechanical performance varying from stiff and brittle to flexible and tough performance. Casein films have an opaque appearance. Irrespective of its relatively high price, it is used today for bottle labeling because of its excellent adhesive properties.

ii.       Gluten plastics exhibit high gloss and show good moisture resistance under certain conditions. They do not dissolve in water, but absorb some water on immersion.

iii.    Soya proteins are commercially available as soya flour, soya concentrate and soya isolate. Soya protein isolate (SPI) may be used to prepare edible and biodegradable packaging films. The films obtained from SPI exhibit excessive friability, so their performance is limited. In order to improve them, they must be modified by the addition of a plasticizer, such as glycerol.

The cheapest protein, keratin extracted from waste streams such as hair, nails and feathers. Keratin the most difficult protein to process due to its structure and a high content of cysteine groups. On the other hand, whey proteins, byproducts from the cheese industry, are widely employed as edible films and coatings. Several lipid components like fatty acids, natural waxes, resins and vegetable oils are generally incorporated in the films to provide hydrophobicity so that moisture barrier properties can be improved.

 Synthetic polymers

They are produced from classical chemical synthesis from bio-based monomers. In this category, polylactic acid (PLA) is one of the most commercially available and exploited bioplastics.

a)       Polylatic acid (PLA): PLA one of the most promising and biodegradable polyester made from renewable resources such as corn, sugar beets, and potato starch for commercial use as a substitute for high density polyethylene (HDPE) and low density polyethylene (LDPE), polystyrene (PS) and polyethylene terephthalate (PET). It is obtained by conversion of corn, or other carbohydrate sources, into dextrose, followed by fermentation into lactic acid. Through direct polycondensation of lactic acid monomers or through ring-opening polymerization of lactide, PLA pellets are obtained. The processing possibilities of this transparent material are very vast, ranging from injection molding and extrusion over cast film extrusion to blow molding and thermoforming. PLA is becoming an advancing alternative as a green food packaging material because it was found that in many circumstances its performance was better than synthetic plastic materials. PLA comes in the form of films, thermo-formed cups and trays, containers and coatings for paper and paper boards etc.

Applications of bioplastics in food packaging

Among the extensively used bio-based plastics, PLA is widely used. Moreover, the bioplastics nowadays have found applications for both short-shelf life products like fresh fruits and vegetables and long shelf life products, like potato chips and pasta.

Food Colour : Importance and Extraction

 Food Colour

Color is an appearance property attributable to the spectral distribution of light. The human eyes are sensitive only to electromagnetic vibrations in the wavelength range of 400 (380) to 760 nm this region of spectrum is known as visible region. The mixture of all colors of different wavelengths in the visible region is known as white light. The approximate wavelength range of different colors are illustrated in below figure.

Importance of Food Colors

Marketing strategy of food by major manufacturers are greatly influenced by color. Color affects almost everything one does in life is the statement given by Downham and Collins i.e., from purchasing items for one’s home, his/her clothing, or their food, decisions are made while giving color the at most importance. Their hypothesis is that all individuals are sensitive to the color of food. Appetites are also influenced and stimulated by color; color may sometimes discourage eating certain foods and diminish the desire for that food.

Colors also suggest the flavors that are anticipated when eating or drinking. Bright orange colored drinks imply the flavor of orange. Simillarly, a bright red colored drink may hint at strawberry or cherry or beetroot flavor. Dull colors of orange or red drinks may indicate a lesser quality of nutrients and so are not as appealing. From past 20 to 30 years many food industry are being processed to create visually appealing food that tastes good that can be used by common man. This briefs out the importance of color to food choices.

 

v  Color is added to food for the following reasons:

a)        To Replace Color Lost During Processing,

b)        To Enhance Color Already Present,

c)        To Minimize Batch-To Batch Variations, And

d)       To Color Otherwise Uncolored Food.

 

v  Food colors are divided into four categories:

1)        Natural Colors:Natural colors are pigments made by living organisms. Usually, pigments made by modification of materials from living organisms, such as caramel, vegetable carbon and Cu-chlorophyllin, are also considered natural though they are in fact (except for carbon) not found in nature.

2)        NatureIdenticalColors:Nature-identical colors are man-made pigments which are also found in nature. Examples are β-carotene, canthaxanthin and riboflavin. 

3)        Synthetic Colors:Synthetic colors are man-made colors which are not found in nature., these are often azo-dyes.

4)        Inorganic Colors: Examples of inorganic colors are titanium dioxide, gold and silver

 

v  Sources of Natural Colour (Pigments)

Pigments are found widespread in nature from the simplest prokaryotic organisms like cyanobacteria and throughout the kingdoms of fungi, plants and animals. Most natural food colorants come from the division Magnoliophyta (flowering plants) of the plant kingdom. However, natural colorants from other sources such as scale insects (cochineal and lac), fungi (Blakeslea trispora and Monascus spp.), and cyanobacteria (Arthrospira spp.) are used today for coloring food.

 

Table : Natural color and their E number

Class	Color	E -number
Chlorophyll	Olive green	E 140
Anthocyanins	Red, purple, blue, pink, magenta	E 163
Carotenoids	Red, orange, yellow	E 160
Betalains	Red, yellow	E 162

 

 

v  

Methods of Extraction of Food Colour (Pigments)

Solvent extraction is the conventional method that is usually followed to extract colors from plant materials. Anthocyanin and betalain pigments, which are water soluble, are extracted from the raw material with water and sometimes with aqueous methanol. For carotenoids extraction, hexane is the solvent of choice and acetone is good choice of solvent for the initial extraction of pigment from the plant material. After thorough extraction of the plant material, the extract is concentrated and subjected to purification steps by using column chromatography. Identification and quantification of the pigment is performed by Spectrophotometry or by high pressure liquid chromatography (HPLC).

 

The current advance techniques that are followed in color extraction are as follows:

1)        High Hydrostatic Pressure (HHP),

2)        Pulsed Electric Field (PEF),

3)        Sonication assisted Extraction,

4)        Gamma Irradiation,

5)        Enzymatic Extraction,

6)        Membrane Technology.

 

High Hydrostatic Pressure (HHP) and Pulsed Electric Field:

Are environment friendly and energy efficient technologies that enhance mass transfer processes within plant or animal cellular tissues, as the permeability of cytoplasmatic membranes can be increased which in turn enhances extraction of valuable cell components. In addition, the decrease in the dielectric constant of water under HHP combined with temperature leads to a decrease in the polarity of the media, contributing to the higher yield of total phenolics and other antioxidants. PEF is reported to enhance mass transfer rates by electroporation of plant cell membranes, improving tissue softness and thus influencing the textural properties. PEF is reported to be an ideal method to enhance juice production, increase the extraction of valuable components better than the yields obtained by enzymatic maceration.

Sonication assisted extraction

Sonication assisted Extraction is one of the most commonly used methods to enhance mass transfer phenomena by cavitation forces, where bubbles in the liquid/solid extraction can explosively collapse and generate localized pressure, causing plant tissue rupture and improving the release of intracellular substances into the solvent.. Its feasibility for the extraction of secondary metabolites such as tea, mint, chamomile and ginseng has been highlighted in many studies.

Gamma Irradiation:

Gamma-irradiation, as a pre-treatment to a plant material, increases cell wall permeabilization, resulting in enhanced extraction of cell constituents in higher yield.

Enzymatic Extraction:

Enzyme assisted extraction of worthy products from plant materials viz., pigments, antioxidants, flavours and phytochemicals is another new technology. Enzyme pre-treatment cannot be a complete substitute for conventional solvent extraction, but can result in increased yield of value added cell components and a reduction in time of extraction and reduction in amount of solvent consumption.

Membrane Technology:

Membrane processing is a fast and emerging technique for the concentration and separation of macro and micro molecules based on molecular size and shape in biotechnology and food processing industries. Advantages of membrane processing are many which include improved product quality with higher yield, utilization of by-products, temperature and pH sensitive products can easily be extracted without alteration and lastly is environmental friendly as no harmful chemicals are being used and less energy is consumed.

Future Perspectives:

The choice of appropriate color to food is very challenging and wrong selection of color may lead to lot of problems viz., lack of consumer appeal and the failure of product. Color suppliers are facing challenges of producing cost effective, good stability, easy to handle, technology for the production of colors. In this aspect, new technologies are welcome with improved benefits over existing technologies.