Canning of fish

Name: T.L.V.Peiris Student Number: GS/Msc/Food/3630/08 University of Sri Jayawardenapura

Canning of fish

3.1. Fish Canning

3.1.1. IntroductionAlthough freezing is the easiest way to preserve fish, canning does offer some advantages. Canned fish is shelf stable and will not take up freezer space. Canning produces a moist, flaky product. Canning also eliminates the bone problem because bones soften and become edible. Mullet (suckers) and other bony fish are often canned in the Great Lakes area for this reason. Canning is a relatively modern process which enables food to be preserve in an edible condition for longer period under various storage conditions.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 is removed 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 solution Autoclave

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 solution for 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.

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Canning of fish

3.1.4. Result

DescriptionPrepared product

Market Product

Weight of Can + Fish +

Brine

483 g 205.46 g

Weight of Can + Fish 346.4 g 150.34 g

Volume of Brine 114 ml 53 ml

Weight of Can 51.078 g 31.33 g

Actual weight of fish 291 g 119.01 g

Drain weight (in label) - 90 g

Actual Net weight 432 g 174.12 g

Net weight (in label) - 155 g

Drained weight % = Drained weight / Net weight * 100%

In prepared product = 291 / 432 *100% = 67.36%

In market product = 119.01 / 174.12 * 100% = 68.35%

3.1.5. Discussion

Fish were brined to dehydrate and make the environment unfit for microbes to grow. Here we reduce the water activity if the solution. Due to this reverse osmosis occur and this retards the microbial load. When filling into can a headspace should be kept since to avoid explosion danger during retorting. Exhausting step is very important to remove soluble gases in the can to avoid oxidation and spoilage.Typical retorting conditions for tuna processed at 115.6° and 121.1 °C in a variety of can sizes

Can dimensions Retorting time

Diam. (mm)

Height(mm)

115.6 °C(min)

121.1 °C(min)

66 40 65 40

84 46.5 75 55

99 68.5 100 85

154 118.5 230 190

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Canning of fish

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 avoid recontamination. 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 flask250 mL titration flask100 mL volumetric flaskWatch glassFunnel 0.1 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 a distinct reddish brown color appeared and persisted on brisk shaking.Titration was repeated.

3.2.4. Results

Determination of Salt Content of Brine

% (m/v) salt in brine = 58.5 X 0.1 X T5

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Canning of fish

T = Mean titre of 0.1M AgNO3

T1 = 1.5 ml T2 = 1.0 ml T3 = 1.3 ml

T = (1.5 + 1.0 + 1.3) / 3 = 1.267 ml

Therefore, % (m/v) salt in brine = 58.5 X 0.1 X 1.267 = 1.49 % 5

3.2.5. Discussion

In this titration at the 1st AgCl is formed and then when we continue addition of Ag this will react with CrO4-2 at the end point (Ag2 CrO4 – reddish brown color). Since the Ksp Value of AgCl is low and Ag2CrO4

-2 is high fist AgCl precipitate is formed.

Sodium Chloride in the brine solution removes water from the tissue and make the environment unfit for microbial growth, due to high salt concentration water activity get redued. 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 fill weights, and fill temperatures for hot fill products, are monitored because both affect the rate 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-process

leaker 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.

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