Plant Pigmentation Lecture 4 PDF

Lecture 4 Plant Pigmentation 1 Allison Morgan 2021  FACILITATOR- Allison Morgan Contact- [email protected] 8768430053 Allison Morgan 2021 2  Plant Pigme...

Lecture 4 Plant Pigmentation 1 Allison Morgan 2021  FACILITATOR- Allison Morgan Contact- [email protected] 8768430053 Allison Morgan 2021 2  Plant Pigments Plant pigments are natural substances in cells and tissues of plants that impart colour. They are important in controlling photosynthesis, growth and development.  Identify the types of Plant Pigments? 1. Chlorophylls 2. Carotenoids 3. Flavonoids (Anthocyanins) 4. Betalains Allison Morgan 2021 3 Chlorophylls  The chlorophylls are characteristic of green vegetables and leaves.  They are green pigments responsible for the colour of leafy vegetable and some fruits eg. Spinach, Lettuce.  Two types of chlorophylls used in food industry as colourants are Chlorophyll a and Chlorophyll b Allison Morgan 2021 4 Carotenoids  Carotenoids are among the most widely distributed pigments and naturally exhibited red, orange and yellow colours.  Carotene is the pigment largely responsible for the colour of butter, cheese, carrots, and cereal grains. Allison Morgan 2021 5 Carotenoids  Carrots, yams, sweet potatoes, papaya, pumpkins, cantaloupe, mangos, tomatoes, bell peppers and oranges are among the fruits and vegetables in which carotenoids can be found. Allison Morgan 2021 6 Flavonoids (Anthocyanins)  Anthocyanins are major polyphenol pigments that largely determine the colors of flowers and fruits. They can be orange, pink, red, blue or purple in color.  They are becoming increasingly popular as food colours replacing synthetic dyes in confectionary, soft drinks, and similar products. Allison Morgan 2021 7 Flavonoids (Anthocyanins)  For example, elderberry, skin of black grapes, purple corn and red cabbage all contain abundant anthocyanin pigments and are utilized as natural food additives. Allison Morgan 2021 8  Anthocyanins Sources Allison Morgan 2021 9 Betalains  These are the pigments responsible for the deep red colour found in vegetables such as beetroot and fruits such as red dragon fruit. Allison Morgan 2021 10 Allison Morgan 2021 11 Effect of heat, acid, alkali, air (aging/storage) on plant pigment Chlorophyll  Based on location in plant tissues, protected from effect of acid. However heating lowers protected effect, and can result in a dirty brown colour when heated at high temperatures.  To prevent browning effect, keep cooking water slightly alkali by adding Sodium Bicarbonate. Allison Morgan 2021 12 Effect of heat, acid, alkali, air (aging/storage) on plant pigment contd. Carotenoids  Generally stable in there natural environment. More soluble in fat than in water so colour does not fade much in response to heat.  Less intense colour under acidic conditions and when exposed to sunlight Allison Morgan 2021 13 Effect of heat, acid, alkali, air (aging/storage) on plant pigment contd. Anthocyanins  Water soluble pigments, heating doesn't change them, but they are red in acidic conditions and blue or purple in alkaline conditions.  Under alkaline conditions, sometimes red cabbage leaves turn blue-purple when cooked, blueberry fruits become green in pancakes and garlic cloves turn green or blue when pickled. Allison Morgan 2021 14 Effect of heat, acid, alkali, air (aging/storage) on plant pigment contd. Betalains  Degraded colour in light and air. Colour is more stable between pH 4 and 6. Below 4 more of a violet colour, above 9 more of a blue colour. Allison Morgan 2021 15  Effect of heat, acid, alkali, air (aging/storage) on plant pigment. Allison Morgan 2021 16 Browning  What causes fruits or vegetables to turn brown once cut?  Enzymes found within the tissue of fruits and vegetables are responsible for helping fruit to ripen and turn brown.  Once cut we release the enzyme-Phenolase. This exposure to air causes an oxidation reaction, and the enzyme to convert phenols also found in cells to melanin which results in the brown colour. This is known as enzymatic browning. Allison Morgan 2021 17 How do we prevent browning and effects on nutrient content?  To prevent browning we need to stop the oxidation reaction from occurring.  This is achieve by denaturing the enzyme. We do this through the use of heat and acids.  Eg Lemon juice can stop enzymes from working properly by changing the pH.  Oxidation also affect nutrients like Vitamin C found in some fruits and vegetables. Once expose to air for prolonged period, the less vitamins it will have available. Allison Morgan 2021 18 Methods of handling and cooking vegetables to retain colour  Processing food always almost alters its nutrient value, colour and texture.  Careful cooking and storage will help to prevent this loss.  Fresh fruits and vegetables have enzymes that can cause loss of colour, nutrients, and flavour changes. These enzymes must be inactivated to prevent such reactions. Allison Morgan 2021 19 Steaming  Steaming vegetables help to mitigate the loss of water soluble vitamins, colour and maintains texture.  Best done by placing vegetables over steam and not directly in water. Allison Morgan 2021 20 Roasting  Dry methods of cooking, such as roasting or grilling, is great at preventing nutrient, flavour and colour loss.  Be sure to coat vegetables with a thin layer of oil to help their surfaces heat more quickly, allowing them to cook faster.  Dry cooking methods also remove moisture, helping create a richer, more intense flavor than other cooking methods. Allison Morgan 2021 21 Blanching  Enzymes are deactivated by blanching.  Blanching is exposure of vegetables to boiling water or steam for a short period of time  Vegetables are then rapidly cooled in ice water to prevent them from cooking. Blanching is essential for preparing good quality frozen vegetables.  Also destroy microorganisms on surface of vegetables. Allison Morgan 2021 22 Freezing  Freezing is a quick and convenient way to preserve fruits and vegetables at home.  You can produce frozen fruits and vegetables of high quality and maximum nutritional value  Blanch vegetables to deactivate enzymes  Limit air during freezing Allison Morgan 2021 23  Gelatin  Gelatin is formed from the partial hydrolysis of collagen and is also allowed as a component of microcapsules for flavorings and for soft capsules in the pharmaceutical industry.  Gelatin formulations in the food industry use almost exclusively water or aqueous polyhydric alcohols as solvents for candy, marshmallow, or dessert preparations.  It is soluble in aqueous solutions, forming a flexible, clear, oxygen-permeable film Allison Morgan 2021 24 Gelatin  In its pure form, it's a pale yellow, odorless, and almost tasteless substance.  Once dry gelatin is mixed with water and other ingredients, it can form some very appealing foods with a pleasant mouthfeel.  Gelatin is produced by boiling collagen obtained from animals. Collagen is the most abundant protein in the animal and human body and is found in connective tissue, which connects and supports other tissues. Allison Morgan 2021 25 Gelatin  Gelatin is sold in a powder form or as sheets called leaves.  When the solid product is added to hot water, a liquid mixture known as a colloid forms. This mixture thickens as it cools and eventually turns into a gel.  Gelatin has many useful functions beyond the kitchen.  It's used to forming gel caps for medications, for example. It's also used in a variety of cosmetics, hair treatments, and crafts. Allison Morgan 2021 26 Gelatin  To disperse dried Gelatin pulverized add boiling water and stir, granular- soak for short.  As a solution of Gelatin cools it becomes more viscous.  When gelation occurs the dispersion of colloidal gelatin becomes an elastic solid. Must be chilled before gel forms. Allison Morgan 2021 27 Uses of Gelatin in Foods  Gelatin is used to make gelatinous desserts, gummy candies, and many yogurts as well as some marshmallows.  It's also added to certain meats to prevent them from drying out and to give them an attractive glaze.  Stocks and consommés form gels as they cool. In canned meats, gelatin absorbs juices released from the meats as they are processed under pressure. Allison Morgan 2021 28 Uses of Gelatin in Foods contd.  Stabilizer to prevent growth of large crystals in ice cream.  Increases viscosity of cream that is too thin to whip. Allison Morgan 2021 29 Gelatin  Amount of liquid needed to gel liquid varies from 1 to 2%.  Too much gelatin gives a stiff rubbery gel.  Gel should be firm enough to hold its shape yet tender and quivery. Allison Morgan 2021 30 Bureau of Standards (BSJ) national standards for fruit and vegetable preservation  BSJ is the statutory body in Jamaica established by the Standards Act of 1969 to promote and encourage standardization in relation to commodities, processes and practices.  They have several regulations that food processors must be guided by when manufacturing food. Allison Morgan 2021 31 Bureau of Standards (BSJ) national standards for fruit and vegetable preservation contd.  The Jamaican Standard for Processed Food (JS 36 1991) is the general standard that applies to most processed food, however based on product type, there may be specific standards for e.g. for fruit and vegetable juice drinks and fruit nectars, there is The Jamaican Standard Specification for fruit and vegetable juice and drinks and fruit nectars ( JS CRS 27 2010).  N.B. a copy of JS CRS 27 2010 has been uploaded to Moodle for additional reading and referencing.  It’s essential that food manufacturers meet the specification standards as stipulated by the BSJ in order for their facility and product to be compliant. Allison Morgan 2021 32