Post harvest oprations.pptx

POST HARVEST OPERATIONS SUCH AS PEELING SIZING AND BLANCHING

1. SUBMITTED BY BHAVANA PRASAD 2016 BDM 11 SIBIN O 2016 BDM 34 PEELING , SIZING AND BLANCHING

2. INTRODUCTION Fruits and vegetables are important constituents of our diet and they serve as a vehicle of nutrients like vitamins, minerals, sugars and  fiber . However, being harvested from farm or field they are prone to contain dirt, soil, bacterial contamination, extraneous matter making them unfit for direct consumption by consumers. For reducing these and to increase the shelf life, all fruits and vegetables undergo some preliminary operations.

3. Post Harvest Preliminary Processing Operations Sorting Grading Washing Peeling Sizing Blanching

4. Sorting Sorting is a separation based on a individual physical properties of raw materials such as weight, size, shape, density, photometric property, etc. Grading grading is classification on the basis of quality incorporating commercial value, end use and official standards.

5. Washing The graded fruits and vegetables are washed with water in different ways, such as soaking and subsequent washing in running water or sprayed with water or dry air to remove surface adhering material.

6. Size reduction Reducing the size into favorable sizes It includes; peeling coring sizing

7. Peeling Removal of unwanted or inedible material or skin of fruits and vegetables Peelers are used

8. Classification of peeling Hand peeling By heat Lye peeling Flame peeling

9. Hand peeling and mechanical peeling This type of operation is performed with various types of equipment which depend upon the result expected and the characteristics of the fruit and vegetables, for example: A machine with abrasion device (potatoes, root vegetables); equipment with knives (apples, pears, potatoes, etc.); equipment with rotating sieve drums (root vegetables).

10. Commercial automatic horizontal potato peeler

11. Peeling by heat Steam or boiling water is used to soften and loosen the skin, which is subsequently removed easily by hand. 40�C for 10-60 seconds where by the skin bursts and retracts facilitating its easy removal by means of pressure sprays. there is practically no loss of flavour and the product is of uniform colour, free from any blemishes. For potatoes and peaches

12. Lye peeling By dipping in boiling caustic soda or lye solution 1 to 2%, for 0.5 to 2 minutes Hot lye loosens the skin from the flesh underneath. Peel is removed by hand Any traces of alkali is removed by washing in running cold water or preferably by dipping it for a few seconds in a very weak solution of hydrochloric or citric acid. Fruits and vegetables such as peaches, apricots, sweet orange, carrots, sweet potatoes, etc.

13. Flame peeling It is used only for garlic and onion which have a papery outer covering. This is just burnt off. about 1 min at 1000° C or to hot gases in rotary tube flame peelers.

14. Losses at vegetable peeling, in %   Peeling methods Vegetables Manual Mechanical Chemical Potatoes 15-19 18-28 - Carrots 13-15 16-18 8-10 Beets 1416 13-15 9-10

15. Blanching Unit operation prior to freezing, canning or drying Fruits and vegetables are heated for the purpose of Inactivating enzymes Modifying texture Preserving colour,flavor&nutritional value Remove traped air Blanching removes traped air within vegetable cells &replaces it with semicontinuos water phase –more uniform crystal growth during freezing Blanching reduces microbial load Onion &pepper will lose flavor on blanching

16. To inactivate enzymes Too little is ineffective, and too much damages the vegetables by excessive cooking, especially where the fresh character of the vegetable is subsequently to be preserved by processing. Depends upon the specificity of vegetables, subsequent processing / preservation methods.

17. D estroy catalase and peroxidase To reduce losses of hydrosoluble substances (mineral salts, vitamins, sugars, etc.) during water blanching, several methods have been developed: T emperature setting at 85-95° C instead of 100° C; B lanching time has to be just sufficient to inactivate enzymes catalase and peroxidase ; A ssure elimination of air from tissues. Microwave treatment is also used

18. WATER BLANCHING Medium - hot water(70-100°C) Uniform treatment Longer processing time-increased leaching of minerals Effluent with high BOD Screw or chain conveyor transport product to hot water tank

19. STEAM BLANCHING 100°C steam(food grade)is injected directly Used for cut and small products Less time than water Chance of over blanching and underblanching due to high temperature gradient Forced convection blanchers are used to increase heat transfer efficiency Individual quick blanching –single layer of product is conveyed through steam chamber More energy efficient Low BOD effluent

20. MICROWAVE BLANCHING Studies started around 1940s Retention of ascorbic acid &carotene and very short process time compared to conventional blanching High potential to improve product quality and minimize waste Not implemented much in industries High equipment cost

21. GAS BLANCHING Hot gas with steam to increase humidity Reduced waste production Needs further research and not used in industry

22. EFFECTS ON FOOD FLAVOUR Blocking off flavours formation due to inactivation of enzymes-the most notable is lipoxygenase Flavour retention increases Remove undesirable bitter flavours from product

23. TEXTURE Blanching results in softened texture Texture assessment include sensory charectarization of firmness , crunchiness and crispiness Lack of crispiness in fruits Blanching of fruit done in calcium chloride solution to firm the fruit COLOUR Direct effect on colour - destruction of pigments by heat Eg:chlorophil Indirect - in potato reducing sugar content adjusted, affects colour develepment during later heating steps where maillard browning takes place NUTRITIONAL VALUE Vitamins degraded by heat mainly vitamin C

24. QUALITY INDICATOR Peroxidase & catalase More resistant to heat than most enzymes Rapid methods to measure their activity

25. Vegetables Temperature, °C Time, min. Peas 85-90 2-7 Green beans 90-95 2-5 Cauliflower Boiling 2 Carrots 90 3-5 Peppers 90 3

26. References www.agrimoon.com https://en.wikipedia.org/wiki/Blanching_(cooking) FOOD PROCESS ENERGY THEORY&LABORATORY EXPERIMENTS –SHRIK SHARMA,SYED S H RIZVI FRUITS AND VEGETABLES HARVESTING,HANDLING,STORAGE-A K THOMPSON HAND BOOK OF FRUITS AND FRUIT PROCESSING-NIRMAL K SINHA,JIWAN S SIDHU,JOSEPH BARTA,JAMES S B WU AND M PILAR CANO

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