Tuna CanningTuna Canning ProcessProcess

Reasons for PrecookingReasons for Precooking

Reduces fat content to improve flavorReduces fat content to improve flavor and reduce oxidation problemsand reduce oxidation problems

Lowers water content so “cook out” doesLowers water content so “cook out” does not occur in the cannot occur in the can

Prevents curd formation in the canPrevents curd formation in the can

Facilitates cleaning Facilitates cleaning

Destroys pathogens and parasitesDestroys pathogens and parasites

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“Typical” Precooking Process forlarge Albacore Tuna

Optimum Temperature Range forOptimum Temperature Range forProteolytic Enzyme ActivityProteolytic Enzyme Activity

In Fish:In Fish:

50-60 50-60 ºCºC

Follow Textural Degradation Follow Textural Degradation during Precooking during Precooking

• Myosin DegradationMyosin Degradation• Kramer Shear TestingKramer Shear Testing• Sensory AnalysisSensory Analysis• Piece/Flake SizePiece/Flake Size• Can YieldCan Yield

Whole Muscle

Bundle

Muscle Fiber (Myofiber)

Myofibril

Thick and Thin Filaments

Thick Filament

Myosin Molecule

Myosin Heavy Chain (MHC)

No Myosin DegradationNo Myosin DegradationProteolytic Myosin DegradationProteolytic Myosin DegradationMyosin decreases with timeMyosin decreases with time

Belly

Dorsal

Tail 44 Precook TemperaturesPrecook Temperatures (50, 55, 60, and 70 (50, 55, 60, and 70 ºC)ºC)

7 Time Intervals (30 min)7 Time Intervals (30 min)

3 Fish Positions3 Fish Positions

Experimental Design:Experimental Design:

Myosin Degradation Rates By Precook Temperature

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Green = 70 ºCFuscia = 60 ºCPurple = 55 ºCAqua = 50 ºC

Treatments Chosen for Further Testing

Kramer Shear Texture TestKramer Shear Texture Test

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Flake

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2 inch 11/2 inch 1 inch 1/2 inch 3/8 inch Pan

Sieve size

Flake size distribution of albacore tuna (belly/dorsal) heated at 70 C

Dorsal 70 C

Belly 70 C

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Flake size distribution of albacore tuna(belly/dorsal) heated at 50 C

Dorsal 50C

Belly 50 C

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Cook Temperature (C)

Mass Loss/under drained conditions of dorsal and belly albacore tuna precooked at 50 C and to 70 C

Dorsal

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7.36.1

5.45.5

Who cares?Who cares?

With the help of NC State With the help of NC State Food EngineersFood Engineers

Janet ZhangJanet ZhangBrian FarkasBrian FarkasPrashant MudgalPrashant Mudgal

• Assume the fish is a Assume the fish is a cylinder cylinder • Break it into finite elements Break it into finite elements • Mathematically model the Mathematically model the temperature of any given temperature of any given location at any given time location at any given time inin the cooking process.the cooking process.

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%Myosin Degradation on Albacore Belly Area (Bad Quality)

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Cooked at 50 C(red)Cooked at 55 C (Blue)Cooked at 60C (pink)Cooked at 70 C (green)50 C F355 C F360 C F370 C F3K50K55K60K70Expon. (K50)Expon. (K70)Expon. (K55)Expon. (K60)

K50 = - 0.00635

K55 = -0.00496

K60= - 0.00495

K70= -0.00179

Teal = 65 ºCOrange = 60 ºCBrown = 55 ºCRed = 50 ºCBlue = 45 ºCGreen = 40 ºCPink = 35 ºCPurple = 30 ºC

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Tuna Dorsal Heated to 60 C

Followed by Cooling at Designated Temperature

Teal = 65 ºCOrange = 60 ºCBrown = 55 ºCRed = 50 ºCBlue = 45 ºCGreen = 40 ºCPink = 35 ºCPurple = 30 ºC

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Tuna Dorsal Heated to 70 C

Followed by Cooling at Designated Temperature

Conclusions:Conclusions:

• Albacore tuna cooked at 70 ºC Albacore tuna cooked at 70 ºC experiences experiences very little proteolytic degradation, very little proteolytic degradation, whereas albacore tuna cooked at 50, 55 whereas albacore tuna cooked at 50, 55 or 60 or 60 ººC have much greater rates of C have much greater rates of degradationdegradation

• The dorsal and tail portions of The dorsal and tail portions of albacore tuna experience the least albacore tuna experience the least amount of proteolytic degradation amount of proteolytic degradation overalloverall

Factors correlated with a high amount of Factors correlated with a high amount of proteolytic degradation include:proteolytic degradation include:

• Soft textureSoft texture

• Smaller Flake sizeSmaller Flake size

• GrittinessGrittiness

• Residual left in mouth after swallowingResidual left in mouth after swallowing

• Lower can yieldLower can yield

During the cooling process, albacore tuna meat During the cooling process, albacore tuna meat continues to degrade until the temperature continues to degrade until the temperature reaches about 30 reaches about 30 ºCºC

Mathematical simulations can be used to predict the Mathematical simulations can be used to predict the time/temperature exposure of different locations of time/temperature exposure of different locations of the tuna based on retort conditions.the tuna based on retort conditions.

This data can be combined with myosin degradation This data can be combined with myosin degradation rates to predict the total textural degradation that rates to predict the total textural degradation that occurs at any given location in the fish during the occurs at any given location in the fish during the precooking process.precooking process.