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FRUITS & VEGETABLES
S U P TA S A R KA R
H H M / 2 0 1 3 / 1 0
M . S C F N - 1 S T Y R
CONTENT:1. STRUCTURE & COMPOSITION
OF CELL TISSUE
2. CHEMICAL COMPOSITION OF PLANT MATERIAL
3. FRUITS
4. VEGETABLES
5. CASE STUDIES:
I. Retention of nutrients in green leafy vegetables on dehydration
II. Evaporative cooling system for storage of fruits & vegetables- a review
STRUCTURE & COMPOSITION OF CELL TISSUE
Fruits & vegetables are composed of both simple & complex cells
Simple tissue: -Dermal tissue -Parenchyma tissue Complex tissue: -Vascular tissue (Xylem & Phloem) -Collenchyma tissue & -Sclerenchyma supporting tissue
COMPONENTS OF PARENCHYMA CELL
CHEMICAL COMPOSITION OF PLANT MATERIAL
1.Carbohydrate: (Simple & complex form)-Complex carbohydrate:• Starch(α-1,4)• Cellulose(β-1,4)• Hemicellulose• Pectic substances2. Protein (<1%)3. Fat (About 5%)
4. Vitamins5. Minerals6. Water (80-90%)7. Phytochemicals8. Pigments -Chlorophyll (green pigment)-Carotenoids (yellow, red or orange)-Anthocyanin (red, blue or purple)-Anthoxanthin (white) Flavonoids
9. Flavour compounds:• Allium• Brassica• Organic acids (Citric acid, malic acid or tartaric
acid)
Sulphur containing
A plant’s turgor pressure is the pressure
that water-filled vacuoles exert on the
cytoplasm & the partially elastic cell
wall.
TURGOR PRESSURE
FRUITS
FRUITS
• A fruit is a part of a flowering plant that derives from
specific tissues of the flower, one or more ovaries, and in
some cases accessory tissues.
• Fruits are the means by which these plants
disseminate seeds.
CLASSIFICATION
1. Berries2. Citrus fruits
3. Drupes4. Grapes5. Melons6. Pomes
7. Tropical & subtropical fruits
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
Generally poor source of iron (Exception is
watermelon, Seethaphul)
Mangoes are excellent source of carotenes.
Oranges are fairly good source of carotene.
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.
Pigments
Fruits contain different pigments:
1. Chlorophyll2. Carotenoids3. Anthocyanins4. Anthoxanthins
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.
Effect of canning or preserving: Colour deteriorate on storage.
Effect of sulphur dioxide: Antimicrobial preservative Potassium metabisulphite at high concentrations 1 – 1.5% causes total irreversible bleaching.
Fruits: 70 to 90% water Found in the vacuoles Soluble substances: sugar, salts,
organic acids & water soluble pigments.
Water
• 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
• Change in solubility is influenced by heat.• Acid make structures more firm.• Alkaline disintegrate the fibre.
Volatile compounds: Esters, aldehydes, acids, alcohols, ketones & ethers.
Sugars, tannins, acids & mineral salts also affect the flavour of fruits.
Flavour constituents
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
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.
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
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.
• 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.
CLIMACTERIC FRUITS NON- CLIMACTERIC FRUITS
AppleApricotBanana
PlumPapayaMangoTomato
Jackfruit
CherryCitrus fruits
FigsGrapesMelons
PineappleStrawberry
Classification of climacteric & non-climacteric fruits:
• Cell wall components undergo changes after harvest due to various enzymes
• Pectin degrade due to pectinesterases & polygalacturonases.
• Other enzymes: cellulase & hemicellulases.
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)
• 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%
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:
ENZYMATIC BROWNINGNormally 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
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
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
NON-ENZYMATIC BROWNING
• Ascorbic acid is responsible for browning
• Mixture of ascorbic acid & amino acid develop browning more rapidly.
VEGETABLES
Vegetables are plants or parts of plants.
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….
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.
Classification based on nutrition:
1. Green leafy vegetables2. Roots & tubers3. Other vegetables
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
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
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
WATER SOLUBLE PIGMENTS
• Flavonoids: -Anthocyanin: Red to purple -Anthoxanthins: Colourless or white
ANTHOCYANIN:• In the vacuoles• Anthocyanidins are anthocyanins without sugar in
their structure• They are pelargonidin(red), cyanidin(reddish
blue), delphinidin(blue).
ANTHOXANTHINS
Anthoxanthins
Flavones
Rutinol
Flavonols
Kaempferol
Flavonones
Naringin
Flavanols
Catechins
Gallocatechins
Leuco-anthocyanin
s
Leuco-cyanidins
ORGANIC ACIDSFormic, 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
ENZYMES
• Composed of protein
• Destroyed by heat & chemicals
• 2 types of enzymes: -Hydrolytic enzymes -Oxido Reductases
Example: Papain, Anthocyanase, Peroxidases, Phenolases, Glycosidases
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
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
CHANGES DURING COOKING
1. Water content2. Carbohydrates
(Cellulose & pectic substances)
3. Protein
LOSS OF NUTRIENTS DURING COOKING
• Mechanical losses• Solvent action of water• Oxidation & chemical
decomposition
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
Effect of heat & oxidation Effect of cooking in fat
2.CAROTENOIDS
FLAVONOIDS
1.ANTHOCYANINS:
Effect of pH Effect of metal Effect of method of
cooking Effect of tap water Effect of pickling
2. BETALAINS Effect of pH
3.ANTHOXANTHINS Effect of pH Effect of metal Effect of cooking on sulphur containing
vegetables Bitter compounds in vegetables
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
FACTORS AFFECTING STORAGE LIFE
• Loss of water
• Respiration
• Microbial spoilage
FUNGI
MUSHROOM:• Umbrella shaped with
a central stalk & a cap called pileus.
• Devoid of chlorophyll• Low calorie• Rich in protein• Less fat
ALGAE
SPIRULINA:• Nutrient dense
food• Rich in protein,
B-carotene & γ-linolenic acid
• Better than 1 soya protein, egg protein or milk protein.
CASE STUDIES:
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
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
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
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
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.
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
CASE STUDY 2
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 & TechnologyMay- June 2013Vol.50, Issue 3PP 429-442
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.
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.
METHOD OF EVAPORATIVE COOLING
Direct cooling systemIndirect evaporative coolingTwo stage system
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
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.
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
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.
CONCLUSION
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
JOURNALS
1. 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
2. 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