2. Common Methods of Post Harvest
Handling
Sorting & Grading
Washing in simple water
Hydro Cooling-sprinkling, dipping,
Cold storage-temp, RH,
Modified atmosphere packaging
Commodity treatments with GRAS chemicals
Cl, CaCl2, KMS, SB, Pot Sor, NaHCO3 , NaCl, h2o2
3. Goal
Improving the quality and value of fresh
vegetables available to consumers
Reducing post harvest losses and improving
marketing efficiency
Solving particular problems in vegetables to
maintain their quality and safety
4. Sorting and Grading
• What are Objectives of Sorting & grading:
1. Enhance product quality & separation according
to market demand
2. maximum utilization & minimize rejection,
3. Obtain maximize profit
4. educe cross contamination of healthy stock
destined for marketing Immediately after
harvest
• It is done in the field or packinghouse with out
any additional expenditures,
5. Continued . . .
• Sorting & grading by hand is extremely labor-
intensive.
• Labor shortages & lack of overall consistency
driven the search for automation of this peration.
• Sorting is done according to size, shape, color,
and appearance.
• Grade standards vary between and within
countries, and local authorities should be
consulted for updates,
• Consumer’s demand is best criteria for sorting &
Grading,
6. Continued . . .
• Many products are sorted according to color,
mass, profile, and size after passing the minimum
requirements of quality.
• The damaged and immature fruits must be
removed, as these might become sources of
ethylene gas, and increase the rate of respiration,
ripening, and senescence of healthy produce.
• Color is a key sorting parameter used in the
implementation of many automated vision
systems that involve image acquisition and
processing.
7. Continued . . .
• Grading determines whether the product
meets a specific quality standard prescribed
by local or international market,
• Sorting helps to separate products into
different quality grades to determine the price
paid to the farmers or to determine the sale
value,
• Sorting enables removal of off grade products, which
include damaged undersized, immature, and
diseased produce
8. Continued . . .
• Optimal maturity, color, sugar, solids,
moisture content, size, and absence of defects
are some of the factors considered for various
fresh market products.
9. Chemicals
To extend the shelf life of fresh vegetables following
chemical can be used
Chlorine wash, Washing in 100-200 ppm chlorine
(mixing 4-8 tablespoons of commercial bleach, 5.25%
sodium hypochlorite ) for 1-3 minutes,
Washing in 2% sodium bicarbonate,
Light chemical treatment in wash water Pottasium
Sorbate, Calcium chloride, Sodium chloride, Acetic
acid, Citric Acid, Sodium benzoate, H2O2
10. The maximum level allowable by law is 0.1%.
Sodium salt of benzoic acid
180 times more soluble in water as compare to
benzoic acid
Lower the pH, the more effective it will be,
Only works if below pH 4.5,
Act as antimicrobial agent,
Sodium benzoate
11. It inactivates trace metals which may cause
haze or deterioration of color and flavor
Up to 40 gm/L can be used for preservation
slow down enzymatic and non-enzymatic
browning, deterioration of texture and
microbial growth on fresh produce.
Citric Acid
12. Added to preserved fruit and vegetables
Conserve colour
Act as antioxidants and control microbial
growth
Sulphur dioxide and its various sulphites
dissolve in water, and at low pH levels yield
sulphurous acid, bisulphite and sulphite ions
The various sulphite salts contain 50-68%
active sulphur dioxide
Sulphur dioxide and Sulphites
13. Continued
At pH values less than 4.0 the antimicrobial
activity reaches its maximum,
Sulphur inhibits enzymatic & non-enzymati
browning during storage,
In the past cut fruits and vegetables in salads bars
were sprayed or dipped in a solution of sulphites
14. Widely used preservative in the world,
Effective against yeast, moulds and bacteria,
Effective up to pH 6.5,
Maximum level allowable by law is 0.1%
Potassium Sorbate
15. Prevent spoilage of vegetables
The antimicrobial activity of salt is related to its
ability to reduce the water activity & reduce
microbial growth,
Reduce the solubility of oxygen in water,
Salting improve taste of vegetables & reduce salt
intolerant molds & bacteria,
Sodium Chloride
16. widely employed as food preservative
>0.3% of acid will inhibit Yeasts, molds and
bacteria growth
Antimicrobial effect is due to lowering the pH
Acetic Acid
17. H2O2
• H2O2 possesses a bactericidal, sporicidal and inhibitory
ability,
• owing to its property as an oxidant and being able to
generate other cytotoxic oxidizing species, such as
hydroxyl radicals [20].
• Treatment with H2O2 can extend the shelf life and
reduce natural and pathogenic microbial populations in
melons, oranges, apples, prunes, tomatoes, whole
grapes and fresh-cut produce H2O2
• It is accepted as a GRAS for some food applications but
not yet approved as an antimicrobial agent
18. 1. Reduce microbial load, and decay
2. Preserves color, texture, shelf life
• Synergistic effect of chemical allow use lower levels
than recommended,
• KMS not allowed on such foods intended for direct
consumption due to sensitivity of asthmatic patients,
• Only dipping for 30 min is sufficient to allow treatment
Advantages of dip chemical treatment
