Presentation on theme: "FST 403:FRIUTS AND VEGETABLE TECHNOLOGY FIRST SEMESTER: 20111/2012 Lecturer: Prof. F.O.Henshaw"— Presentation transcript:
FST 403:FRIUTS AND VEGETABLE TECHNOLOGY FIRST SEMESTER: 20111/2012 Lecturer: Prof. F.O.Henshaw Mobile phone:
COURSE OBJECTIVES FST 403: A compulsory core course for the B.Sc Food Science and Technology programme At the end of the course students should have: –Acquired an understanding of the nature and properties of the food commodity class, Fruits and vegetables –Acquired an understanding of the post harvest physiological changes in fruits and vegetables –Been exposed to various processing and preservation technologies appropriate for fruit and vegetables –Acquired the required skills in post harvest handling and storage of different fruits and vegetables –Developed critical thinking in relating post harvest handling to quality of fresh and processed fruits and vegetable products
COURSE OUTLINE 1Classification of Fruits and Vegetable 2Structure of Fruits and Vegetables 3Chemical Composition 4Post harvest Physiology 5Storage of fresh fruits and vegetable *Controlled Atmosphere *Modified Atmosphere 6Pretreatment methods: Blanching,sulphiting
7Preservation Technologies Freezing Canning Dehydration sun drying mechanical drying Osmo dehydration 8Fruit and Vegetable Products Fruit juice and Drinks Fruit leather
9Sugar Preserves jam, jellies and marmalade 10Fermented vegetables Pickles,
COURSE REQUIREMENTS 75% attendance of Lectures condition to qualify to seat for final examination. Distribution of course grade Take home assignment 10% In Class Quiz 20% Final Examination 70%
CLASSIFICATION FRUITS: Botanically, are mature ovaries and seed bearing parts of plants Include: grains, legumes, nuts Cucumbers, olives, mangoes, peppers, tomatoes, citrus, bananas grapes, strawberry, pineapple,
The course however does not include fruits of the grass family such as Cereals, nor the Legumes and nuts The succulent, high moisture and generally sweet fruits and consumed raw as dessert rather than main meals.
Vegetables: are all other parts of plant which are edible Include; roots, stems, tubers, leaves etc These are generally consumed, processed in one form or the other and part of main meal.
This course does not include the starchy roots and tubers This class of commodity (Fruits and Vegetable) have the following characteristics: high moisture content highly perishable
Post harvest changes in Fruits and vegetable can be desirable e.g Ripening of fruits, which leads to changes necessary for optimum eating quality, colour change, taste and flavour development
Structure of Fruits and vegetables Fruits and Vegetables are made of Simple and Complex cells –Simple cells Dermal tissue Parenchyma tissue Dermal tissue is the single layer outside surface of leaves, stem, roots, etc
Parenchyma tissue form majority of the plant tissue and is where the basic molecular activity take place: Synthesis –Storage of carbohydrate (Photosynthesis) occur.
Chemical composition Water Carbohydrates Organic acid Fiber Pigments Vitamins Minerals Pectic substances
Food Carbohy drate ProteinFatAshWater Cereals wheat flour, white rice, milled, white maize, whole grain Earth vegetables potatoes, white sweet potatoes Vegetables carrots radishes asparagus beans, snap, green peas, fresh lettuce Fruit banana orange apple strawberries
Phytochemicals: non nutrient plant chemicals Beneficial in disease prevention Subject of Scientific research on effects on human health
Structure of chlorophyll
Chlorophyll –green pigment in plant found in the chloroplast, it is responsible for photosynthesis Fat soluble Structurally a porphyrin ring containing magnesium at the center Displacement of magnesium from the center leads to irreversible pigment change Change to a gray-green called pheophytin conversion to pheophytin is favoured by acid Phbut does not occur easily under alkaline condition
Other factors that can cause colour change; –Heat of cooking –Change in pH –Minerals ( zinc and copper) Carotenoids –Red, orange, and yellow pigments in fruits and vegetables –Occur in chloroplast along with chlorophyll,where the chlorophyll dominates –Also in chromoplasts without chlorophyll
Carotenoids are responsible or the colour of tomatoes, peppers, citrus, carrots. E.g beta –carotene- orange colour, structurally an unsaturated hydrocarbon, the conjugated double bonds are responsible for the colour Beta-carotene is a precursor of vitamin A (retinol), cleaved by enzyme in the intestinal mucosa to yeild vitamin A Lycopene- red-orange colour of tomatoes and water melon,
Xanthophylls: yellow orange colour Derivatives of carotene Reponsible for colour of yellow maize (cryptoxanthin) Are vitamin A precursor Carotenoids are fairly stable, resistant to to heat, pH changes, water leaching since they are fat soluble carotenoids may undergo autoxidation due to large nos of double bonds Can lead to off-flavour Antioxidants are usually applied to prevent oxidative changes
Structure of carotenoids
Flavonoids:- group of compounds, pigments and colour precursors –Water soluble –E.g; Anthocyanins: red, blue-red, purple pigments such as in blueberries, cherries, raspberries, plums and grapes –structrally
Structure of Anthocyanin
Structure of e.gs of Anthoxanthin
Harvesting, handling and Postharvest changes Different harvest regimes for Fruits and vegetables Appropriate maturity stage required for optimum quality Respiration continue after harvest i.e taking in O 2 and giving off CO 2, heat and moisture mechanical damage during harvesting hastens respiration rate and spoilage
Ripening: major post harvest change in fruits Ripening pattern vary, 2 categories –Climacteric ripen after harvest –Non Climacteric ripen before harvest Climacteri c Non- Climacteric Apples Banana Mango Peach Plum Pawpaw avocado Citrus Cherry Pineapple melon strawberry
Ripening involves biochemical changes Enzymic, hormonal Leading to colour changes, flavour development and optimum eating quality
Storage of fresh produce must seek to control post harvest changes Controlled storage conditions ca extend the shelf life of produce –Modified atmosphere packaging: Principle is to replace the internal atmosphere of fresh produce by flushing with nitrogen or carbon dioxide and this will lead to extension of shelf life
After flushing the material is sealed in a package to prevent oxygen entry Normal air composition (78%, Nitrogen; 20% oxygen and 0.03% carbon dioxide) is modififed within the package to: –Reduces respiration –Retards growth of aerobic organisms
Controlled atmosphere storage: Principle is similar to MA storage involve modification of the gas composition. Reducing oxygen and increasing carbon dioxide in the store Combined with low temperature.