Ultrahang a garnélarák felolvasztásának és hámozásának javítására

Traditional brining-based maturation of shrimp can loosen the shell–meat connection but requires long soaking times and careful salt control to avoid color fading, sweetness loss, and compromised texture. Recent advancements demonstrate that power ultrasound can replace or enhance maturation by accelerating both thawing and shell-loosening while preserving shrimp quality. Get science-backed insights how sonication improves processing efficiency and end-product quality of frozen shrimps.

Shrimp Peeling and its Challenges

Shrimp peeling is one of the largest cost drivers in crustacean processing. Cold-water species like Pandalus borealis exhibit a very strong muscle–shell attachment, making freshly caught shrimp extremely difficult to peel mechanically. To solve this, processors traditionally use brining or ice maturation for up to 1–3 days, allowing endogenous enzymes and salt diffusion to weaken the attachment. However:

• long soaks risk loss of red/yellow color,
• excessive salt uptake changes flavor and reduces sweetness,
• extended time increases microbial risk, and
• ice crystallization during freezing can damage tissue without adequate salt concentration.

A modern alternative is sonication, which acts physically (cavitation, microjets, shear forces) rather than chemically, providing both rapid thawing and accelerated shell loosening with minimal product degradation.

 

 

How Ultrasound Improves Thawing of Shrimp

Rapid heat transfer through cavitation

Ultrasound produces microscopic bubbles in the liquid surrounding the shrimp. These bubbles expand and collapse violently – a phenomenon called acoustic cavitation.
According to Li et al. (2024):
Ultrasound reduced thawing time from 87 min (air thawing) and 66 min (flow water thawing) down to 48 min, representing a 48.9% acceleration.

 

 

This occurs because collapsing cavitation bubbles:

• generate shockwaves and microjets,
• thin the thermal boundary layer around the food,
• and accelerate melting of internal ice crystals.

Protection against lipid/protein oxidation

Li et al. (2024) show that combining ultrasound with slightly basic electrolyzed water (SBEW) prevents:

• MDA (lipid oxidation marker) dropped to 0.62 nmol/mg in ultrasound + SBEW vs 0.83 nmol/mg in air-thawed shrimp.
• Carbonyls (protein oxidation) were lowest in ultrasound-assisted SBEW-treated shrimp (1.63 nmol/mg vs 3.21 nmol/mg for air thawing).

Preservation of muscle structure and water retention

Ultrasound thawing (UST):

• maintains muscle fiber integrity, 
where ultrasound-assisted SBEW-treated samples show tightly aligned fibers similar to fresh shrimp.
• results in the lowest thawing loss (4.06%) and lowest cooking loss compared to all other methods.

 

 

Ultrasonically-Improved Peeling of Shrimp

1. Cavitation physically weakens the shell–muscle interface

   Dang et al. (2018) found that power ultrasound at 24 kHz creates:

   • spiral pits on the shell surface,
   • erosion of the epicuticle layer,
   • increased porosity,
   • microchannels extending toward the membranous layer.

   These structural changes dramatically improve shell release.
   SEM images on page 37 clearly show pits on US-treated and US+enzyme-treated shrimp, while raw and enzyme-only samples remain smooth.

 

2. Ultrasound reduces peeling work and increases yield

   When used before or during enzyme maturation:

   • Peeling work decreased from 7.8 mJ/g (raw) to 3.9 mJ/g, a 50% reduction.
   • Meat yield increased (up to ~90% depending on condition).
   • Proportion of completely peeled shrimp increased significantly.



   Ultrasound alone already improves peelability; combined ultrasound + enzyme is even more powerful.

 

3. Enzyme diffusion enhanced through ultrasonic microchannels

   The proposed mechanism results in:

   1. Cavitation pits form “entry points” in the shell.
   2. These pits connect to deeper microchannels.
   3. Enzymes–whether endogenous or added–penetrate faster and hydrolyze the muscle-shell attachment.

   This allows:

   • shorter maturation (hours instead of 1–3 days),
   • less risk of color fading or sweetness loss,
   • lower salt requirements than brining.

 

4. Minimal impact on color and texture

   Unlike long salt soaks, ultrasound treatments:

   • did not change L*, a*, b* color parameters compared to raw shrimp,
   • did not damage texture (hardness, resilience, chewiness stayed comparable).

   This makes ultrasound far safer than over-maturation in brine, which is known to dull color and reduce sweetness.

Sonication Compared to Brining

Ultrasound provides a more controlled, faster, and cleaner mechanism than salt diffusion.

Paraméter	Traditional Brine Maturation	Ultrasound-Based Methods
Idő	12-48h	3-4h (US + enzyme)
Salt usage	Magas	Low or none
Risk of over-soaking	Magas	Very low
Peeling work	Mérsékelt	Reduced by up to 50%
Color preservation	Often reduced	Maintained
édesség	May decrease	Maintained
Szövet	loss of springiness	Preserved
Microbial risk	Higher (long process time)	Lower (short process)