Fruits & Vegetables PDF

FNSC2001 Intro to Food Science & Technology Fruits & Vegetables Dr. Erika Kwek Food & Nutritional Sciences Programme School of Life Sciences 3943 4403 ∙ erikakwe...

FNSC2001 Intro to Food Science & Technology Fruits & Vegetables Dr. Erika Kwek Food & Nutritional Sciences Programme School of Life Sciences 3943 4403 ∙ [email protected] Definitions Vegetables Edible part of a herbaceous plant (plants with flexible green stems with few to no woody part). Usually grouped according to the part of plant that is eaten (e.g. leaves, stem, roots …). Source: Veggies Grow Fruits Mature ovaries of flowering plants. Defined as “a plant reproductive body” (Britannica) Ovaries contain the seed or seeds that has developed after fertilization. One of the main purposes is to spread the seeds of the plant.  Vegetable-fruits Cucumber, eggplant, pepper, pumpkin, tomato Flowers Seeds Broccoli Beans, peas, corn Leaves Stems and Shoots Spinach, cabbage Asparagus, celery Tubers Bulbs underground enlarged fleshy stems with an underground stems; starch storage organ bulb of food reserve (e.g. potatoes) (e.g. garlic, onion, lily) Roots underground organs (e.g. carrot, radish, beetroot) Classifications of Fruits 1. Simple Fruits 2. Aggregate Fruits 3. Multiple Fruits 4. (Accessory Fruits) Classifications of Fruits (Structure)  *Pistil: female reproductive part of flower (has ovary (potential seeds)). * Carpel & Pistil https://slideplayer.com/slide/13028470/ Female reproductive part of a flower. Carpel: ovary, stigma, style. Pistil: one or many carpels. One carpel Many carpels Fruit development: 1. Fertilization of the carpel 2. Maturing & ripening of flower ovary Classifications of Fruits (Structure) Other Classifications 5. 3. 1. Stone Fleshy Berries Fruits Fruits (Drupes) 2. 4. Citrus Pomes Fruits  1. Fleshy fruit without stone (pit) – Berries *seeds are not hard and large True berries: Simple fruits stemming from one flower with one ovary and typically several seeds. *entire ovary wall in a single flower ripens into a fruit.  2. Citrus “Citrus”: genus of plants (e.g. lemons, mandarins, oranges, lime, grapefruit…) Fruits Typically has sour taste and sharp flavor (high quantity of citric acid and other organic acids). Waxy outer layer needs to be peeled off before eating. Good sources of vitamin C.  3. Fleshy Any fruit that has thick, soft and Fruits succulent tissue (edible part) can be considered ”fleshy fruits”. Fleshy fruits are larger in size. Sometimes seeds are small, soft, and edible along with the flesh. e.g. melons, papaya, etc.  Fruits that has a central “core” seed(s), 4. surrounded by edible flesh, enveloped by tough outer layer. Pomes *Core is usually not eaten. e.g. Apples and Pears 5. Stone Fruit that has pulp on the outside and inedible large, hard ”stone” in the middle. Fruits e.g. plums, cherries, (Drupes) peaches, walnuts, mangoes https://www.healthline.com/nutrition/eat-the-rainbow https://www.mdpi.com/1420-3049/27/13/4061 Nutrients and Health Benefits 1 3 2 Carotenoids Fat soluble. Most widely found pigments in nature. Exhibits yellow, orange, red and purple colors. Antioxidant properties: protect cells from damage by free radicals. *(Heat or oxidation affects the chemical structure) Bell Peppers Corn Asparagus Tomato Papaya Broccoli Carotenes Lycopene Xanthophylls Lutein (Vitamin A) Zeaxanthin Chlorophylls Fat soluble Slightly soluble in alkaline medium Less stable than carotenoids Natural pigments responsible for green color in plants & algae In a plant: chlorophyll absorbs light for photosynthesis. Many health benefits – antioxidant…  Flavonoids Water soluble *(Tend to be lost in cooking water) Antioxidant properties (may improve cardiovascular health). Natural compounds in plant products (e.g. tea, citrus fruits, vegetables). Types of flavonoids: Anthocyanin, Source: Sapian Syaifuzah Anthoxanthin, Betalains, etc. Berries Cauliflower, Onion Beet root Anthocyanin Anthoxanthin Betalains Flavonoids Nutrients & Health Benefits Good sources for: ▪ Dietary fibre (proper bowel function, reduce constipation) ▪ Potassium (maintain healthy blood pressure) ▪ Folate (maintain normal cell division, reduce the risk of neural tube defects) ▪ Vitamin A (keep eyes and skin healthy, protect against infections) ▪ Vitamin C (heal cuts and wounds, keep gums and teeth healthy, iron adsorption) ▪ Phytochemicals (anti-inflammatory, anti-oxidation, anti-cancer effects) Usually low in fat and calories (lower calorie intake, weight control) No cholesterol (reduce the risk of heart disease) For best nutrition: Vegetables Buy variety of fresh vegetables in season. Select vegetables with more potassium often (e.g. sweet potatoes, white potatoes, beans, tomato products, beet greens, soybeans, spinach…). Sauces or seasonings can add calories, saturated fat, and sodium to vegetables. Prepare more foods from fresh ingredients to lower sodium intake. Most sodium in the food supply comes from packaged or processed foods. Buy canned vegetables labelled "reduced sodium," "low sodium," or "no salt added.”  For best nutrition: Fruits Make most of your choices whole or cut-up fruit rather than juice*, for the benefits that dietary fibre provides. Vary your fruit choices to get different nutrients. Select fruits with more potassium often (e.g. bananas, prunes, peaches and apricots…) When choosing canned fruits, select fruit canned in 100% fruit juice or water rather than syrup. Fruit juices: Fresh, frozen concentrate… 10-100% actual juice. Normally no fibers. May provide some Vit A/C Characteristics & Features Pectin compounds Water-soluble gel-forming polysaccharides within and between plant cell walls. Serving as a cementing substance, contributing to the plant’s firmness and elasticity to tissues – structural function. Juice cloudiness can be reduced by adding pectinase enzyme to degrade and remove pectin compounds. Pectin formation in ripening fruits Use of Pectin Jams & Jellies Stabilizer (frozen food) Thickener C Texturizer Tannins & Enzymatic Browning Tannins: a naturally occurring polyphenol predominantly found in unripe fruits, giving a bitter taste and leaving an astringent feeling in the mouth. E.g. grapes, apples, apricots, avocados, bananas, cherries, dates, papayas, peaches, pears, strawberries. Enzymatic browning: Tannins + Polyphenol oxidase (PPO) enzymes + Oxygen  Crispiness Juiciness Intercellular air spaces Stored water and other compounds (e.g. salts, add volume & crispness to organic acid, saccharides and red-blue pigments). vegetables & fruits. Affect the amount of liquid a cell holds, which Without air spaces, the determine juiciness. texture becomes soft and Low in potatoes and bananas, high in watermelons flaccid. and tomatoes. o Apple: 20-25% o Peach: 15% Provides turgor and crunchiness to leafy o Potato: 1% vegetables (the rigid firmness of a plant cell is due to water). Heat or humidity reduces turgor. Acidity in fruits The tart flavour is partially due to the organic acid in vacuole. Acidity usually decreases as the fruit ripens. Either volatile or non-volatile. Volatile acids vaporise during heating: o Most fruits: pH < 5 o Most vegetables: pH 5.0 - 5.6 o Corn, potatoes: pH 6.1 - 6.3 Common organic acids Citric acid: citrus fruits, tomatoes Malic acid: apples, cherries Tartaric acid: grapes Oxalic acid: rhubarb (vegetables) *can combine with calcium in intestine to form calcium oxalate, which is an insoluble complex that cannot be absorbed. Preparation & Storage How to avoid Browning? 1. Heat: dipping fruits briefly in boiling water to denature the enzymes 2. Acid: optimal pH for PPO is 7. Soak or coat the fruits with orange, lime, lemon juices. 3. Cold temperature: reduce the rate but can’t completely inhibit browning 4. Sugar/water: separate fruits from oxygen 5. Antioxidants: ascorbic acid and sulphur compounds (may cause allergy). Used in dried fruits.  How to keep & enhance Green color? Blanching: foods are briefly cooked in boiling water and then plunged in iced water to stop the cooking process. Chlorophylls can be masked by the air between the cells. Blanching causes the air to bubble away. Keep heating time short. Add a small amount of sugar/salt. Cook green vegetables uncovered for the first few minutes to allow volatile organic acids to escape. How to Store fruits & vegetables? Climacteric ▪ continue to ripen after being harvested. ▪ Ripening: increased respiration rate & ethylene release (plant hormone). Non-climacteric ▪ respire at the same or lower rate after being harvested. ▪ (most vegetables and some fruits) Non-chilling Chilling Sensitive Sensitive  Storage of Fruits Ripe fruit with a high water content is best to consume < 3 days of purchase. Once ripe, put them in plastic bags punctured with air holes, and then in refrigerator. Unripe fruit can be left at room temp in a paper bag until ripe. Grapes spoil quickly regardless if they’re ripe or not. Store them in refrigerator, unwashed, in plastic bags and wash prior to consumption. Bananas are best stored at room temp, otherwise their skins will darken. Storage of Vegetables Temperature: Faster the respiration, quicker the deterioration Humidity: Vegetables keep losing water after harvested. (Optimal humidity for most vegetables and fruits: 85-95%) Water content: Vegetables with high water content have shorter storage time, e.g. lettuce, spinach vs. carrots Vegetables in the Fridge Most vegetables can last ≥3 days if refrigerated. Remove the green tops of carrots, radishes or beets. Store in the crisper drawer, which is designed to maintain moisture. Wrap moist vegetables in paper towels to avoid dehydration. Put them in plastic bags with air holes. Keep in Cool & Dry Place Eggplants deteriorate quickly in either warm or cold places. Keep in aerated bags. Unripe tomatoes: keep out of sunlight, which will soften them. Refrigeration will destroy its enzymes required for ripening. Onions: never refrigerate and never store it together with potatoes. Potatoes: keep in a basket or bag with holes. ❖ When refrigerated, starch will be converted to glucose and develop an undesirable waxy taste. ❖ When exposed to sunlight, a bitter taste is produced, and eventually form potential toxic compound – solanine.