FREEZING OF OKRA

اشراف الدكتور سليمان اللوصي

سائد محمود زبيدات محمد ناصر زبيدات

الزبيدات بامية اخوان

OUTLINE

1. Food

2. Food preservation

3. Freezing

4. Okra

5. Food deterioration

6. Blanching

7. Frying

8. Experimental Work

9. Discussion

10. Conclusion

Known food, where

every item has a taste

acceptable and easily

chewed & digested, and

absorbed in the blood, in

order to obtain a

balanced food and a

good nutritional value.

FOOD PRESERVATION

Methods of food preservation

Acidification

Drying

Canning

Freezing

FREEZING

A food preservation method used for increasing

the shelf-life of the product, by decreasing the

temperature and stop the microbial growth.

Some unit operations are applied before

freezing.

Our project is talking about freezing of Okra

and the study of the morphology of Okra.

FREEZING

Two methods of freezing are known: slow

freezing & rapid freezing

Rapid freezing

1. Small ice crystals

2. Both extra and ultra cellular ice crystals

3. Better quality

4. Produce freezing burn less than slow freezing

FREEZING

Slow freezing

1- Large ice crystals are formed

2- Ice crystal formation in extra cellular formation

3- low quality of product

4- Freezing burn occurs

EXAMPLE OF FREEZING VEGETABLE

Broccoli

Cabbage

Cucumber

Potatoes

Okra

TYPE OF OKRA

OKRA

Okra in French (Gombo) (lady’s finger) is a plant floral eaten off the green.

Scientific name: Abelmoschus esculentus, kind annual or with grown in one season

Plant height up to 2 meters and more. Securities petition reaches a length between 10 to 20 cm.

Okra have a high nutritional value and health benefits

OKRA PRODUCTION

Okra is produced in many warm-weather countries e.g. India, Pakistan, Turkey, Iran, Nigeria, Ghana, Greece, and southern USA,and is considered one of the most important vegetables in Egypt, because of its nutritional content and medicinal potentials against inflammation.

It is one of the major products concerning al-Zubeidat Company.

MICROBIAL ACTIVITY & ENZYMATIC BROWNING

1. Microbial activity: Microorganisms, such as

bacteria, yeast & mold are omnipresent and

may have good or bad effect on our food.

2. Enzymatic browning : Fruits and vegetables

contain enzymes, which accelerate damage of

its tissue and loss of texture and color.

ENZYMATIC BROWNING

Enzymatic browning is a biochemical process in

which plant (fruit or vegetable) tissues take on

a brown color when exposed to oxygen.

Other types of browning in foods include

Maillard browning (proteins and sugars at high

temperatures), carmelization (sugars at high

temperatures).

ENZYMATIC BROWNING

Enzymatic browning occurs when plant tissue is

exposed to air resulting in a brown colored

pigment, being produced as a result of a series

of biochemical reactions. Phenolases which are

enzymes found outside the cell wall come in

contact with colorless phenols which are found

inside the cell causing the brown color to

appear.

HOW TO PREVENT ENZYMATIC OXIDATION

The polyphenol oxidase enzyme can be

inactivated by:

1. certain organic acids; such as ascorbic acid

and citric acid that are commonly used in food

industry to prevent browning of fruits and

vegetables.

2. Heat treatment such as blanching.

BLANCHING

Blanching is the exposure of the vegetables to boiling water or steam for a brief period of time to inactivate enzymes. Practically every vegetable needs to be blanched and promptly cooled prior to freezing, since heating slows or stops the enzyme action.

Enzymes can cause loss in quality, flavor, color, texture, and nutrients. If vegetables are not heated sufficiently, the enzymes will continue to be active during frozen storage

BLANCHING

Blanching may be done by using:

Hot water….. at a temperature of 85°C/4 min.

Steam …..at a temperature of 100°C/6 min.

EFFICIENCY OF BLANCHING AND HOW IS DETERMINED?

After freezing is finished some test use to

determine efficiency of blanching this test :

1.Catalase

2. Peroxidase

3. Sensorial properties.

PEROXIDES TEST& CATALASE TEST :

If color changes, it means the presence of enzyme.

Peroxidase test

Pink color colorless

+ve -ve

Inefficient efficient

Catalase test

Formation of gas bubbles is an indicator of

enzyme activity.

FRYING

Main Purpose of frying: altering of organoleptic

quality (color, flavor & texture…)

Secondary purpose

1. Inactivation of enzymes and microorganisms

2. Reduce moisture content.

FLOWCHART OF FREEZING

Preparation Cleaning/washing ,cutting, slicing,

dicing)

Blanching Frying at 145ºC for 4min Hot water

at 85ºC for

4 min

Steam at

120ºC

for 4min

Draining

Vacuum packaging

Freezing at

-18ºC

PREPARATION

BLANCHING 85C/4MIN &COOLING

DRAINING

PACKAGING

Proper packaging of frozen food is important to

protect the product from contamination and

damage while in transit from the manufacturer

to the consumer, as well as to preserve food

value, flavor, color, and texture. There are

several factors considered in designing a

suitable package for a frozen food

POLYETHYLENE

Polyethylene bags have a variety of uses. They are flexible, transparent and have a perfect resistance to low temperatures and impermeability to water vapor. An important advantage is that these bags can be easily heat-sealed. Utilization is in forms of sheets and bags.

VACUUM PACKAGING

STEAMING 100C/6MIN

FRYING 145C/4 MIN DEEP

VACUUM PACKAGING

PREPARATION OF SOLUTION

Sensorial test PeroxidaseCatalase

Texture Color

SoftGoodNo color changeAbsence of gasHot water

GoodGoodNo color changeAbsence of gasSteam

Very softGoodNo color changeAbsence of gasPartial Frying

RESULT

RESULT

DISCUSSION

The best way to inactivate enzymes is by blanching (hot water).

Mucilage is suitable for medicinal and industrial applications. It has been used medically.

The pods must be removed by cutting to prevent browning.

In steam, the pods must be mixed to allow the steam to reach all parts of okra evenly.

CONCLUSION

Our experimental part was conducted very late

because okra was unavailable.

After blanching, mucilage still appears but by

frying mucilage is lost.

We choose the study of Okra and one of its

preservation methods, because it is one of the

most important products at al-Zubeidat Co.

Palestine investment fund promised our Company

to fund a project of freezing of vegetables.