canning of food

8/9/2019 Canning of Food

http://slidepdf.com/reader/full/canning-of-food 1/4

Canningof

Food

B.K.K.K.

Jinadasa

GS/M.Sc./FOOD/36

08/08



February 1, 2010 [CANNING OF FOOD]

3.1. Fish Canning

3.1.1. Introduction

The technology for preserving foods in cans was developed at the beginning of the nineteenthcentury when a Frenchman, Nicolas Appert, won a competition initiated by another greatcharacter in French history, Napoleon Bonaparte. Canning is a relatively modern process whichenables food to be preserve in an edible condition for longer period under various storageconditions.Generally three processes are involved.

1] Sealing in the can.2] Heat sterilization.3] Cooling to the ambient temperature.

In the fish canning, fish to be put in to the can in fresh condition. Then the within the can isremoved by exhausting and after that can is seamed using a seamer. After seaming cans are

subjected to sterilization

3.1.2. Materials

FishSS VesselsKnivesCutting boardsSalt solution [saturated]2% salt solutionAutoclave

3.1.3. Method

Fresh fish were degutted, cleaned, washed, and weighed.Then fish were cut in to suitable sizes for canning and fish were dipped in saturated salt solutionfor 10 min, after that filled in to cans.Cans with fish were pre cooked at 950 C for 10 min and oven dry at 130 0C.2% salt solution was prepared and added in to cans and exhausted [20 min from the point of boiling]. Then the lids were fixed and sterilized at 121 ºC for 20 min.

Then the cans were cooled using water and stored.

3.1.4. Result

Weight (g)

Fish + Tin + Brine 199.26

Fish + Tin 131.79Tin 32.63

Fish 99.16

Brine 67.47

Page | 2




% fish in tin

3.1.5. Discussion

Fish were brined to dehydrate and make the environment unfit for microbes to grow.When filling into can a headspace should be kept.Exhausting step is very important to remove soluble gases in the can to avoid oxidation andspoilage.Seaming operation is also important. This operation is to be done properly to avoid leakages.Sterilization temperature and time are very critical for the shelf life of the canned product.Water which is used for cooling after sterilization should be thoroughly cleaned, to avoidrecontamination.Shelf life of canned fish is about 2 years, however it is better to consume within first year due to

nutrient reduction [each year nutrient reduction take place by 20%].

3.2. Determination the salt content of the brine.

3.2.1. Introduction

Solutions of sugar or brine are used in preserving canned food. Concentration of the salt or sugar solution determines the shelf life of these foods. Therefore, concentration of these salt and sugar solution is one of the important factors used in the evaluation of their quality.

3.2.2. Materials

Canned fish50 mL burette10 mL & 25 mL pipette250 mL volumetric flask 250 mL titration flask 100 mL volumetric flask Watch glassFunnel0.1 M Silver NitratePotassium Chromate indictor

3.2.3. Method

5 mL of brine sample was pipette out and diluted to 250 mL. 25 mL of diluted brine was pipette out in to 250 mL titration flask.1 mL of potassium chromate indicator was added and titrated with 0.1M silver nitrate until adistinct reddish brown color appeared and persisted on brisk shaking.Titration was repeated.

Page | 3




3.2.4. Results

1st reading - 6.85 mL2nd reading - 6.80 mL3rd reading - 6.75 mLMean reading - 6.80 mL

% mvsalt in brine =58.5 x 0.1 x T5

T = mean titration volume of 0.1M AgNO3

= 58.5 x 0.1 x 6.805

Salt % = 7.96%

3.2.5. Discussion

In this titration brine solution was diluted to get the reading into reliable limit and to save AgNO3

since it is very expensive.

In this titration at the 1st level AgCl is formed and then convert in to Ag CrO4 at the end point(Ag CrO4 – reddish brown color).

Sodium Chloride in the brine solution removes water from the tissue and make the environmentunfit for microbial growth, due to high osmotic pressure.Soluble protein and amino acids are concentrated in the brine solution.

The following is therefore a summary of the major operations in fish canning;1. Raw Material Handling - There is a direct, and unavoidable, relationship linking raw

material quality and end product quality.2. Pre-treatment - Pre-treatment covers the range of operations during which the product, is

prepared for canning. Examples of pre-treatment, include, gutting, washing, nobbing,filleting, shucking, shelling (peeling), cutting, brining and dipping.

3. Pre-cooking - Pre-cooking is usually carried out in steam, water, oil, hot air or smoke, or a combination of these.

4. Filling - Whether filling operations are manual or automatic it is most important that fillweights, and fill temperatures for hot fill products, are monitored because both affect therate of heat transfer to the SHP of the can during retorting.

5. Sealing –

6. Retorting - The five stages of retorting which are Preparation and loading, Venting,Come-up, processing and cooling.

7. Post-process Handling - There are several contributory factors leading to post-processleaker spoilage; these include the following, poor quality cooling water, poor post- process hygiene and sanitation and container damage during handling and storage.

8. Final Operations - Container damage during handling and storage, rate of cooling,temperature of storage are considered.

Page | 4

canning of food

Documents