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FST 151FOOD FREEZINGFOOD SCIENCE AND TECHNOLOGY 151

Special topics: Cryogenic ProcessingLecture Notes

Prof. Vinod K. Jindal(Formerly Professor, Asian Institute of Technology)Visiting ProfessorChemical Engineering DepartmentMahidol UniversitySalaya, NakornpathomThailand

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Thomas E. RippenUniversity of Maryland Sea Grant

Andrew TolleyEquipment Project Coordinator

Bill SielingChesapeake Bay Seafood Industries Association

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Strengths◦ Can produce fresh, unpasteurized crabmeat◦ Growing demand for local, fresh foods◦ Local crabmeat recognized for high quality

Weaknesses◦ Crabs are seasonal, best crabs when demand◦ Still need a way to extend shelf-life and

inventory products◦ Pasteurized crabmeat perceived as more

highly processed, less fresh◦ Traditional cans are expensive, available from

only one manufacturer

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Crabmeat containers

1 lb plastic cup

Fresh pack, used

for freezing in this test.

401 diameter

pasteurized can

307 diameter pasteurized can

307 diameter MD pasteurized can

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Panama 307 closing machine

Canco 60P 401 closing machine

$27,400, between “as is and rebuilt” condition (Alard)

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Dehydration◦ Water migration and recrystallization◦ Hydrophobic interactions

Concentration of reactants (What happened to Q10?)◦ Enzymatic softening in some fish◦ Formation of cross-links (e.g. formaldehyde from TMAO)◦ Oxidation of oils (rancidity)

Protein denaturation and structural damage – ◦ Toughening◦ Excessive drip◦ Bland flavor

Oxidative changes◦ Yellowing◦ Off-flavors and odors

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Pass through 27-15F quickly. Target final equilibrium temp = storage

temp Use good barrier packaging Hold storage temperatures steady

◦ Fluctuating vapor pressure accelerates sublimation and accretion of ice crystals (a-axis and c-axis growth)

Hold storage temperature as cold as commercially feasible.

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Rapid freezing Currently used in Maryland and elsewhere

with good experience Product is thawed and sold as previously

frozen Studies show reduced tissue damage

◦ SEM (Giddings and Hall, 1976) And improved sensory quality for short-

term holding (1½ months)◦ Webb, et. al. 1976

Beyond 5-6 months, pasteurization may be better option

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Mini Freezer

Liquid

Nitrogen

Dewar

Vent

Relief

Valve

LN2 Hose

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15

16

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Interpretation of Data

Pasteurization as Baseline

3 Year Payback

Comparison of Equipment Combinations

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Basic Information Generated from Phase 1

1 Process was determined for this equipment

Initial temperature, 31-34 º F

Freezer cabinet was set at -100 º F

The process time was 60 minutes

The batch size was 75 pounds

2 Liquid nitrogen usage was determined

5.2 pounds of crabmeat were frozen per gallon of liquid nitrogen

LN2 cost $4.98 per gallon

Approximately 19 batches of crabmeat were frozen (1425 lbs)

The cost of LN2 (without equipment or other charges) is $.96 per lb of crabmeat

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3 Other equipment and storage options identified

Mini freezer (75 lb capacity) used in Phase 1

Batch freezer, single door (200 lb capacity)*

Batch freezer, double door (400 lb capacity)*

LN2 Dewars, 41 gallon, used in Phase 1

LN2 Bulk tank, 1500 gallon

4 Pros and Cons of equipment

5 Extended costs of equipment options

Fixed cost - outright purchase of freezers and installation

Lease costs-( 5 year contract) for bulk tank

Consumable costs- liquid nitrogen used for freezing

Basic Data Generated from Phase 1, con’t

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1

3

2Mini and Bulk

Mini freezer

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Mini Cabinet Batch Cabinet

75 lb max capacity 200 lb max capacity

75 x 8 hours = 600 lbs per day 200 x 8 hours = 1600 lbs per day

Minimum vent requirements - flexible

Fixed vent through roof

Requires stooping to load and unload

Can utilize portable cart

Portable Fixed location

Comparison

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Bulk Tanks for Liquid Nitrogen

Pros Cons

Inventory management is less complicated

Higher cost of concrete pad

Relief exhaust not in process area

Higher piping installation costs

“Lower pressure” nitrogen is colder

5 year lease arrangement, due 12 months per year even if not in production

Nitrogen costs 1/5 of dewar inventory

Space will be dedicated to bulk tank pad and fence

Not necessary to change tanks in middle of process

Nitrogen is delivered by semi-truck

Tanks are “Pressure vessels” and are owned and inspected by nitrogen supplier

Used smaller tanks (are available) for purchase but subject to owner inspection

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Mini Freezer

75 lbs capacity

Batch Freezer

200 lb capacity

Double Door Freezer

400 lb capacity

Too Small

Too LargeJust Right

Freezer Cabinets

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Liquid Nitrogen Storage

Dewars

BulkTank

41 Gallon Capacity 1500 Gallon Capacity

Cheap LN2 vs 5 yr lease

Expensive NL2 vs low rent

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Recommendation:

Bulk and batch cabinet

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Pasteurized vs Batch/Bulk NL2Fixed Cost and Variable Cost

2,500

5,000

7,500

10,000

12,500

15,000

17,500

20,000$2.00

$4.00

$6.00

$8.00

$10.00

Variable Cost of Pasteurizing

Fixed Cost of Pasteurizing

Variable Cost of Batch Freezer/Bulk Tank

Fixed Cost of Batch Freezer/Bulk Tank

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Conclusion

• Mini Cabinet is too small

• Dewars are not practical for LN2 storage for crabmeat processors

• A batch cabinet and bulk tank system are recommended

• A production range for a LN2 freezer system is at least 7,500 lbs to 10,000 lbs per year (either in a single operation or a combination)

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Compared to traditional packaging (metal can) how

would you rate this plastic tray?

Much poorer packaging

Poorer packingNo difference

Better packaging

Much better packaging

0

10

20

30

40

50

Num

ber

of R

espo

nses

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Compared to traditional packaging (metal can) how would you

rate this plastic tray?

0

2

4

6

8

10

12

14

16

Much betterpackaging

BetterPackaging

No difference Poorerpackaging

Extremely poorerpackaging

Num

ber

of R

espo

nses

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Consumers indicating that the tray was better or much better than the metal can

Eastern Shore: 68 percentWestern Shore: 48 percent

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CSF consumer survey ◦ Survey Taken During Seafood Cooking

Demonstrations at Harbor Day Event◦ 64 completed the survey

Community Supported Agriculture◦ Exploring potential for adding a seafood

option◦ Survey instrument prepared and sent to 350

members of existing CSA on Eastern Shore

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1. Which locally caught species would make you more likely to participate in a CSF program in your area. Crabmeat 44; Striped bass 31; Live crab 26, Clams 25; Shucked oysters 20; Live oysters 20

2. I prefer: fillets/steaks 41; whole fish 16; headed/gutted 10; no preference 6

  3. How often would your prefer to have these

types of seafood available (mixed products each week/seasonally). Bi-weekly 32; weekly 20; monthly 5; quarterly 1.

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4. Product available for pickup by you at set time and location. Average drive miles – 10; weekday afternoons - 33; weekend mornings - 30

  5. On a scale of 1 to 10, would you sign up for a

CSF arrangement/contract based on the species you chose above.One (very unlikely) - 4; Two- 4 ; Three-3; Four-4; Five-4; Six-0; Seven - 13; Eight - 3; Nine - 4; Ten (very likely) - 22

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Evaluate batch freezer performance under commercial conditions.

Conduct retail sales study comparing skin-pack trays to metal cans.

Conduct and monitor one or more alternative marketing strategies.