Operations performed on foods before processing Before processing, raw materials undergo a number of operations to get a high quality product

1. PREPARATORY OPERATIONS IN FOOD
PROCESSING
Abid Hussain

2. FOOD PROCESSING
 Its not new to humans
 Early processing techniques: Sun drying, Salting
and Fermentation
 Recent include: pasteurization, canning and
concentration
 Freeze drying and irradiation are the modern
developments

3. FOOD PROCESSING
 “Process of transforming fresh food into
wholesome, nutritious and acceptable products
which are safe for human consumption”.

4. FOOD PROCESSING

5. PREPARATORY OPERATIONS
 Before processing, raw materials
undergo a number of operations to
get a high quality product
 Major operations used commonly are:
1. Cleaning
2. Sorting & Grading
3. Peeling
4. Size Reduction
5. Blanching

6. 1. CLEANING
 Removal of undesirable (visible & invisible)
materials from food is called cleaning.
 It includes the removal of:
1. Damaged food
2. Insect-infested
3. Deteriorated food
4. Stones & Metal pieces
5. Removal of soil
6. Getting rid of pesticides, fungicides etc..
7. Improving the appearance

7. 1. CLEANING
 Cleaning also includes washing while processing
fruits, vegetables, cereals, pulses and meat
products.

8. 2. SORTING & GRADING
 Sorting ___ categorization of food based on
measurable physical property like; shape, size,
color & weight
 Grading ___ process of separating the food based
on quality

9. 2. SORTING & GRADING
 Sorting by size and shape is carried out using
flatbed screens (flour, sugar, spices) or drum
screens (nuts, pea, pulses)
 Grading is done by screen grader, roller grader and
length grader.

10. 3. PEELING
 Removal of protective covering from fruits &
vegetables by using knives or peelers
 Different methods are used for peeling:
1. Scalding
2. Abrasion Peeling
3. Flame Peeling
4. Lye Peeling

11. 3. PEELING
 Scalding: dipping of fruits and vegetables in boiling
water for short period so as to ease the peeling
process. e.g; tomatoes & potatoes
 Abrasion Peeling: a large scale peeling by using
special machines (a cylindrical equipment with
rough surface) e.g; potatoes

12. 3. PEELING
 Flame Peeling: it employs a high temperature to
burn off outer hair and peels that are then removed
by high pressure water. Used for onions.
 Lye Peeling: boiling of vegetables in 1-2% NaOH
solution to decompose pectin substances below the
epidermis and loosens the skin. Used for potatoes,
tomatoes and carrots.

13. 4. SIZE REDUCTION
 For an easy and quick cooking of food ingredients,
their size should be reduced by using suitable
knives, slicers, choppers, dicers or grinders. Its
benefits include:
1. Easier & faster cooking
2. Improved appearance of product
3. Adds garnishing
4. Ensures uniform cooking

14. 5. BLANCHING
 Heating of some plant food materials in hot water or
steam for a short period of time.
 Blanching serves to:
 Destroy active food enzymes
 Loosen the skin, e.g. tomatoes
 Remove adhering contaminants like soil, insects, etc.
 Remove tissue gas and reduce volume and facilitate
close filling
 Fix the green color in vegetables

15. 5. BLANCHING
 Blanching time at home is 2-5 minutes in boiling
water, while it is same for industry in live steam.
 Effectiveness of blanching is determined by
evaluating activity of peroxidase or catalase
enzymes.

16. 5. BLANCHING
 Certain chemicals are also added to blanching
water to improve the process.
 Calcium chloride is added to firm fruits.
 Ascorbic acid, Sodium chloride, Magnesium oxide,
Sodium metabisulphite, Sodium bicarbonate and
some others are used to preserve color and
retention of vitamin C.

17. 6. SULPHURING / SULPHITING
 With some dried products, the use of chemical
preservatives will improve the color and increase the
shelf-life.
 The most commonly used preservative is sulphur
dioxide.
 There are two methods: sulphuring and sulphiting.
 Sulphuring is more commonly used for fruits, and
sulphiting for vegetables.
 Sulphiting involves the use of sulphite salts, such as
sodium sulphite or sodium metabisulphite. They may be
either added to the blanching water or more commonly
used by soaking the food in a solution of the salts.

18. 6. SULPHURING / SULPHITING
 Sulphuring is achieved by burning sulphur in a sulphur
cabinet. This can be made from locally available
materials.
 The amount of sulphur used and the time of exposure
depend on
 the commodity
 its moisture content
 levels permitted in the final product
 The food is placed inside the cabinet and sufficient
sulphur is placed in a container near the trays. For most
vegetables 10-12 g of sulphur (22½ level teaspoons) per
kg of food is adequate. The sulphur is ignited and
allowed to burn in the enclosed cabinet for 1-3 hours.