Fruits & vegetables

Chapter- Fruits & Vegetables

1. FRUITS & VEGETABLES Supta Sarkar HHM/2013/10 M.Sc FN-1 st Yr

2. CONTENT: STRUCTURE & COMPOSITION OF CELL TISSUE CHEMICAL COMPOSITION OF PLANT MATERIAL FRUITS VEGETABLES CASE STUDIES: I. R etention of nutrients in green leafy vegetables on dehydration II. Evaporative cooling system for storage of fruits & vegetables - a review

3. STRUCTURE & COMPOSITION OF CELL TISSUE Fruits & vegetables are composed of both simple & complex cells Simple tissue: -Dermal tissue -Parenchyma tissue Complex tissue: - V ascular tissue (Xylem & Phloem) -Collenchyma tissue & -Sclerenchyma supporting tissue

4. COMPONENTS OF PARENCHYMA CELL

5. CHEMICAL COMPOSITION OF PLANT MATERIAL 1.Carbohydrate: (Simple & complex form) -Complex carbohydrate: Starch( α -1,4) Cellulose( β -1,4) Hemicellulose Pectic substances 2. Protein (<1%) 3. Fat (About 5%)

6. 4. Vitamins 5. Minerals 6. Water (80-90%) 7. Phytochemicals 8. Pigments -Chlorophyll ( green pigment ) -Carotenoids ( yellow , red or orange ) -Anthocyanin ( red , blue or purple ) - Anthoxanthin ( white ) Flavonoids

7. 9. Flavour compounds: Allium Brassica Organic acids (Citric acid, malic acid or tartaric acid) Sulphur containing

8. A plant’s turgor pressure is the pressure that water-filled vacuoles exert on the cytoplasm & the partially elastic cell wall. TURGOR PRESSURE

9. FRUITS

10. FRUITS A  fruit is a part of a  flowering plant  that derives from specific  t issues  of the  flower , one or more  ovaries , and in some cases accessory tissues. Fruits are the means by which these plants disseminate  seeds.  

11. CLASSIFICATION Berries Citrus fruits Drupes Grapes Melons Pomes Tropical & subtropical fruits

12. COMPOSITION & NUTRITIVE VALUE Fruits are very poor source of protein & fat. (Exception: Avocado) Contain high amount of moisture Good source of fibre Not very good sources of calories (Exception: Banana) Higher percentage of sugar

13. Generally poor source of iron (Exception is watermelon, Seethaphul ) Mangoes are excellent source of carotenes. Oranges are fairly good source of carotene.

14. Citrus fruits are good source of vitamin C. If fruits are bruised, peeled, cooked or exposed to air, alkali or copper large amounts of vitamin may be oxidised . Apples give fibre to the diet.

15. Pigments Fruits contain different pigments: Chlorophyll Carotenoids Anthocyanins Anthoxanthins

16. Anthocyanins Enzymes like anthocyanase catalase reactions that result in the loss of colour of anthocyanins . In addition to heat & oxygen various metallic ions can cause undesirable change in colour . The metal iron precipitates anthocyanin. This reaction may cause ‘pin-holing’ of cans.

17. Effect of canning or preserving: C olour deteriorate on storage. Effect of sulphur dioxide: Antimicrobial preservative Potassium metabisulphite at high concentrations 1 – 1.5% causes total irreversible bleaching.

18. Fruits: 70 to 90% water Found in the vacuoles Soluble substances: sugar, salts, organic acids & water soluble pigments. Water

19. The framework of fruit is made of cellulose Forms the wall of plant cell Pectic substances are also found in cell walls & between cells. Act as cementing substance. Pectic substances: protopectin , pectinic acid, pectic acid. Cellulose & pectic substances

20. Change in solubility is influenced by heat. Acid make structures more firm. Alkaline disintegrate the fibre .

21. Volatile compounds: Esters, aldehydes, acids, alcohols, ketones & ethers. Sugars, tannins, acids & mineral salts also affect the flavour of fruits. Flavour constituents

22. Comprised of catechins , leuco-anthocyanins & hydroxy acids. They are present in the tissues of those woody plants while absent in herbaceous plants. Tannins affect the colour & flavour High amount: skin & seeds Polyphenols or Tannins

23. Effects of polyphenols on fruit quality: Undesirable astringency in some fruits & desirable astringency in ciders & wines. Brown discolouration due to oxidation . Undesirable dark coloured complexes with iron due to sequestering action in canned food. Leucoanthocyanins cause development of pink to pinkish brown colour .

24. Bitterness in fruits: - Limoninoids ( triterpenes ) & - flavanone glycosides (flavonoids) The precursor of limonin in intact citrus tissue combine with acidic pH of fruit The principal bitter tasting flavonoid compound: naringin

25. Post harvest changes & Storage All synthesis of organic compounds halts after harvest but numerous physiological changes continue during storage. Bulbs, roots, tubers & seeds become relatively dormant during storage whereas fleshy tissues undergo ripening after maturation & then continue to senescence. Certain biochemical activities occur.

26. Respiration rate varies with stage of maturity. Based on the rate of respiration prior to senescence fruits are classified as: Climacteric & Non-climacteric fruits. Non-climacteric fruits are best when ripened before harvesting.

27. CLIMACTERIC FRUITS NON- CLIMACTERIC FRUITS Apple Apricot Banana Plum Papaya Mango Tomato Jackfruit Cherry Citrus fruits Figs Grapes Melons Pineapple Strawberry Classification of climacteric & non-climacteric fruits:

28. Cell wall components undergo changes after harvest due to various enzymes Pectin degrade due to pectinesterases & polygalacturonases . Other enzymes: cellulase & hemicellulases .

29. RIPENING OF FRUITS It is genetically programmed highly coordinated physiological process Changes occur due to enzymes: lipase, pectic enzymes, invertase , chlorophyllase & peroxidase Breakdown of chlorophyll( colour changes from green -> yellow or orange red ) Softening of flesh ( protopectin -> pectin, & in over ripe fruits: pectin -> pectic acid)

30. There is decrese in acidity, increase in sugar, increase in volatile substances & increase in essential oil The optimum temperature is about 20°C & relative humidity about 90-95%

31. Each fruit must be stored at its own optimum temperature Proper air circulation must be ensured Commercial storage: Low temperature close to 0°C & relative humidity about 85% is preferred Home refrigerator: Ventilated covered containers Strong flavoured fruits can be stored in tight containers. STORAGE:

32. ENZYMATIC BROWNING Normally the natural enzymatic compounds present in intact tissue do not come in contact with the enzyme phenol oxidases present in some tissues Phenol oxidase enzyme act on polyphenols, oxidising them to orthoquinones Orthoquinones rapidly polimerise to form brown pigments. The optimum pH is between 5 to 7

33. Schematic diagram of enzymatic browning: Cut fruit containing catechins , tyrosine, chlorogenic acid , mono & dihydroxy phenol DOPA ( Dihydroxy Phenyl Alanine) Orthoquinones Melanins polyphenolase polyphenolase polymerised O2 O2

34. Prevention of enzymatic browning : Either by inactivating the enzyme or cutting off the oxygen: Temperature Change in pH Use of antioxidants Prevention of contact with oxygen

35. NON-ENZYMATIC BROWNING Ascorbic acid is responsible for browning Mixture of ascorbic acid & amino acid develop browning more rapidly.

36. VEGETABLES Vegetables are plants or parts of plants.

37. Botanical classification of vegetables: CLASSIFICATION: GROUP EXAMPLES Roots Carrot, beet root, radish turnip, colocasia Tubers Potatoes, sweet potato , tapioca Bulb Garlic, onion, shallots Leaves Cabbage, lettuce, spinach Flowers Plantain flower, cauliflower, neem flower, brocoli Contd ….

38. GROUPS EXAMPLE Fruits Tomatoes, brinjal , lady’s finger, pumpkin, bottle gourd Legumes (pods & seeds) Peas , beans, bengal gram tender, red gram tender Stems Plantain stem, amaranth stem, celery stem Fungi Mushroom Algae Spirulina …Contd.

39. Classification based on nutrition: 1. Green leafy vegetables 2. Roots & tubers 3. Other vegetables

40. Most of the pigments occur in plastids Some of the water soluble pigments are dissolved in the vacuoles The chief pigments: -Fat soluble -Water soluble PIGMENTS

41. WATER INSOLUBLE PIGMENTS CHLOROPHYLL Present in chloroplasts 2 chlorophylls: -Chlorophyll-a: Intense blue green -Chlorophyll-b: Dull Yellow green Occurs in the ratio: 3a:1b

42. CAROTENOIDS Groups of yellow, orange, red & fat soluble pigments They are present as α -carotene, β -carotene, γ -carotene, xanthophyll & cryptoxanthin β -carotene is valuable in the synthesis of vitamin A

43. WATER SOLUBLE PIGMENTS Flavonoids: -Anthocyanin: Red to purple - Anthoxanthins : C olourless or white ANTHOCYANIN: In the vacuoles Anthocyanidins are anthocyanins without sugar in their structure They are pelargonidin (red), cyanidin (reddish blue), delphinidin (blue).

44. ANTHOXANTHINS

45. ORGANIC ACIDS Formic, Succinic, Citric, Acetic, Malic, Fumaric , Tartaric & Benzoic acid The concentration is lower in vegetables than fruits Tomatoes & vegetables with concentration of acid have pH 4 - 4.6 Most vegetables have pH of about 5 – 5.6

46. ENZYMES Composed of protein Destroyed by heat & chemicals 2 types of enzymes: -Hydrolytic enzymes - Oxido Reductases Example: Papain, Anthocyanase , Peroxidases, Phenolases , Glycosidases

47. FLAVOUR COMPOUNDS The natural flavours of vegetables are due to mixture of aldehydes, alcohol, ketones, organic acids& sulphur compounds Astringent taste is due to phenolic compounds & tannins. Strong flavour due to sulphur containing compounds as in Allium & Cruciferae vegetables

48. Flavour components in sulphur containing vegetables Vegetables Precursor Reaction with treatment Final volatile compound Garlic Alliin S-2-propenyl ( allyl ) cysteine sulphoxide Cutting / crushing results in allicin formation. This undergoes non-enzymatic decomposition to disulphide & thiosulphinate Disulphide further decomposes to a complex mixture of mono- sulphide & tri- sulphide –characteristic flavour Onion S-1-propenyl cysteine sulphoxide Cutting/ crushing results in formation of sulphenic acids which is unstable & undergoes rearrangement Thiopropanal -S-oxide- lachry matory factor Brassica family- cabbage, cauliflower S-methyl-cysteine sulphoxide & thioglucosides Cooking Dimethyl sulphides & isothiocyanates - give off- flavour

49. CHANGES DURING COOKING Water content Carbohydrates (Cellulose & pectic substances) Protein

50. LOSS OF NUTRIENTS DURING COOKING Mechanical losses Solvent action of water Oxidation & chemical decomposition

51. 1.CHLOROPHYLL Effect of putting in hot water Effect of prolonged cooking & acid Effect of canning Effect of sodium bicarbonate Effect of freezing Effect of copper Effect of calcium salt EFFECT OF COOKING ON PIGMENTS

52. Effect of heat & oxidation Effect of cooking in fat 2.CAROTENOIDS

53. FLAVONOIDS 1.ANTHOCYANINS: Effect of pH Effect of metal Effect of method of cooking Effect of tap water Effect of pickling

54. 2. BETALAINS Effect of pH 3.ANTHOXANTHINS Effect of pH Effect of metal Effect of cooking on sulphur containing vegetables Bitter compounds in vegetables

55. STORAGE OF VEGETABLES Loss of moisture Flavour gets impaired because of enzyme action & conversion of sugar to starch Mature vegetables deteriorate less in storage than immature vegetables STORAGE: In covered containers or plastic bags in refrigerator

56. Factors affecting storage life Loss of water Respiration Microbial spoilage

57. FUNGI MUSHROOM : Umbrella shaped with a central stalk & a cap called pileus . Devoid of chlorophyll Low calorie Rich in protein Less fat

58. ALGAE SPIRULINA: Nutrient dense food Rich in protein, B-carotene & γ - linolenic acid Better than 1 soya protein, egg protein or milk protein.

59. CASE STUDIES:

60. Study conducted by Sheetal Gupta, B.S.Gowri , A.Jyothi Lakshmi, Jamuna Prakash Journal of Food Science & Technology September- October 2013 Vol 50, Issue 5 PP 918-925 1. RETENTION OF NUTRIENTS IN GREEN LEAFY VEGETABLES ON DEHYDRATION

61. To investigate the influence of dehydration on nutrient composition of Amaranthus gangeticus , Chenopodium album( bathua ), Centella asiatica ( centella ), Amaranth tricolor( tampala ) & Trigonella foenum graecum (fenugreek) OBJECTIVE

62. The GLV were were steam blanched for 5 min & dried in an oven at 60°C for 10-12hrs. The fresh & dehydrated samples were analysed for selected proximate constituents, vitamins, minerals, antinutrients & dialyzable minerals STUDY METHODOLOGY

63. Dehydration seems to have little effect on the proximate constituents, vitamins, minerals, antinutrient content of the GLV Among the vitamins, retention of ascorbic acid was 1-14%, thiamin 22-71%, total carotene 49-73% & β -carotene 20-69% of their initial content. FINDINGS

64. Dialyzable iron & calcium in the fresh vegetables ranged between 0.21-3.5mg & 15.36-81.33 mg/100g respectively which reduced to 0.05-0.53mg & 6.94-58.15mg/100g on dehydration.

65. Proximate principles were least affected Calcium & total iron content decreased slightly Dialysability of minerals decreased significantly Among the vitamins, ascorbic acid, total & B-carotene were lost significantly while thiamine was retained moderately Changes in the antinutritional factor was not significant. CONCLUSION

66. CASE STUDY 2

67. EVAPORATIVE COOLING SYSTEM FOR STORAGE OF FRUITS & VEGETABLES - A review Study conducted by: Amrat lal Basediya , D.V.K.Samuel , Vimala Beera Journal of Food Science & Technology May- June 2013 Vol.50, Issue 3 PP 429-442

68. EVAPORATIVE COOLING SYSTEM Evaporative cooling is a well-known system to be an efficient & economical means for reducing the temperature & increasing the relative humidity in an enclosure & this this effect has been extensively tried for increasing the shelf life of horticultural produce in some tropical & subtropical countries.

69. PRINCIPLE OF EVAPORATIVE COOLING The wet-bulb temperature as compared to air’s dry-bulb temperature, is a measure of potential for evaporative cooling. The greater the difference in the temperature, the greater is the cooling effect.

70. METHOD OF EVAPORATIVE COOLING Direct cooling system Indirect evaporative cooling Two stage system

71. Evaporative cooling system for short duration: (Scientific storage system) ZERO ENERGY COOLING SYSTEM: Developed at IARI, New Delhi By Roy & Khurdiya (1986) Based on the principle of evaporative cooling

72. ADVANTAGE OF EVAPORATIVE COOLED STORAGE Most suitable for rural application Size can be fitted to the need Better marketablity Retain nutritive value Environment friendly Reduce energy use by 70% Extends shelf life (Reduces surrounding air temperature & increases moisture content) Less expensive & easy to install, operate & maintain.

73. DISADVANTAGE: Requires a constant water supply to wet pad Space required outside home Water high in mineral leave mineral deposit High humidity decreases the cooling capability No dehumidification

74. CONCLUSION Approximately 23-35% of horticultural produce goes waste due to improper post harvest operation & storage Evaporative cooling system is well suited where temperature is high, humidity low, water can be spared & air movement available Zero energy cool chamber could be used for short duration storage in hilly regions.

75. CONCLUSION

76. TEXT BOOKS: 1. Vaclavik,V.A ., Christian,E.W ., Essentials of Food Science , Third Edition, Springer. 2. Srilaksmi , Food Science , Third Edition, 2003, New Age International Publisher, New Delhi. REFERENCE

77. JOURNALS Gupta,S ., Gowri,B.S ., Lakshmi,A.J ., Prakash,J ., 2013, Retention of nutrients in green leafy vegetables on dehydration, Journal of Food Science & Technology, Vol.50(5), PP 918-925 Basediya,A.L ., Samuel,D.V.K ., Beera,V ., 2013, Evaporative Cooling System for Storage of fruits & vegetables, Journal of Food Science & Technology, Vol.50(3), PP 429-442