Sonication for Juice Preservation and Nutrient Enhancement

In modern food processing, preserving freshness while enhancing nutritional value is a central challenge. High-performance ultrasonication — using probe-type sonicators — has gained traction as a powerful non-thermal processing method. This article presents findings from a scientific study investigating how the nutritional profile of strawberry juice sweetened with Stevia rebaudiana is enhanced by Hielscher ultrasonic processors.

Key Insights: Sonication boosts phenolic content, flavonoid levels, and antioxidant capacity — all under scalable conditions suitable for industrial deployment.

Why Replace Heat with Ultrasound?

Traditional pasteurization can degrade thermolabile compounds like polyphenols and flavonoids. Ultrasonication, by contrast, is a non-thermal processing technique that uses acoustic cavitation to enhance cell disruption and molecular diffusion without heat damage.

A recent peer-reviewed study by Šic Žlabur et al. (2019) published in the journal “Molecules” provides robust evidence on the efficacy of high-intensity ultrasound, using the Hielscher sonicator model UP400St, for treating strawberry juice sweetened with Stevia rebaudiana. The findings carry significant implications for industrial juice processing, given that the experimental conditions are linearly scalable with the Hielscher ultrasonic systems used.

Benefits of Ultrasonic Juice Processing:

• Enhanced extraction of bioactive compounds
• Preservation of flavor and color
• Reduction in microbial load
• Scalable and energy-efficient
• Clean-label, additive-free process

The Experimental Setup: Juice Sonication

The study employed a Hielscher UP400St ultrasonic processor (400 W, 24 kHz) to treat strawberry juice in the presence of green stevia powder.
The researchers evaluated the effects of probetype sonication under various amplitudes (50%, 75%, 100%), probe diameters (sonotrode S24d7 with 7 mm and S24d22 with 22 mm tip size), and sonication times (15, 20, and 25 minutes). Across all tested conditions, the most intense treatment — 100% amplitude, 22 mm probe, 25 minutes — yielded the most pronounced results.

Results Overview – Ultrasonic Juice Processing

Enhanced Total Phenolic Content (TPC)

Sonicated juices demonstrated up to 23% higher TPC compared to mild sonication and 18% higher than non-sonicated juices with stevia.

C18: Sonicated with 22 mm probe, 100% amplitude, 25 minutes
Table: Effect of Sonication on Phenolic Content and Antioxidant Activity

 
Total phenolic content (TPC) increased by 23% compared to the mildest sonication and 18% compared to non-sonicated samples with stevia.
Key phenolics enhanced included luteolin, apigenin, quercetin, myricetin, and kaempferol, with increases ranging from 3- to 7-fold.
Antioxidant capacity (via ABTS assay) also increased, displaying the rise in bioactives.

Phenolic Acids and Flavonoid Profile

Ultrasound enabled superior extraction of phenolic acids such as pyrogallol and 4-methyl-catechol, with pyrogallol reaching nearly 2 mg/g in the most intensely sonicated juice — over 3.5× higher than in non-sonicated counterparts.

The formation of hydroxyl radicals during acoustic cavitation likely contributes to enhanced hydroxylation and release of phenolic compounds, which aligns with previous mechanistic studies on ultrasonic extraction.

Improved Sweetness with Functional Benefits

Notably, the study explored steviol glycosides, particularly stevioside and rebaudioside A (Reb A) — the primary sweeteners in Stevia rebaudiana. Sonication significantly boosted their concentrations:

• Stevioside content increased by 61%.
• Reb A content doubled (+114%).

This enhancement is not only beneficial from a sweetness perspective but also from a sensory and metabolic angle. Higher Reb A levels improve palatability by reducing the bitterness often associated with stevioside.

Ultrasonic Juice Processing: Industrial Relevance and Scalability

Hielscher sonicators allow for a precise control over all important process parameters. Thereby, all results are linearly scalable, owing to the design of Hielscher ultrasonic processors, which maintain constant energy intensity during scale-up. This makes the transition from bench-top to continuous industrial systems both technically feasible and economically attractive.

This study adds to a growing body of evidence supporting high-intensity ultrasound as a sustainable, non-thermal processing method. The combined benefits observed — nutrient enhancement, improved antioxidant capacity, and optimized sensory properties — underscore its value in functional beverage development.

So, what does this mean for industry?
With scalable technology platforms like those from Hielscher, juice manufacturers can now consider sonication not merely as an alternative, but as an upgrade—both for product quality and consumer health.

The table below gives you an indication of the approximate processing capacity of our ultrasonicators:

Design, Manufacturing and Consulting – Quality Made in Germany

Hielscher ultrasonicators are well-known for their highest quality and design standards. Robustness and easy operation allow the smooth integration of our ultrasonicators into industrial facilities. Rough conditions and demanding environments are easily handled by Hielscher ultrasonicators.

Hielscher Ultrasonics is an ISO certified company and put special emphasis on high-performance ultrasonicators featuring state-of-the-art technology and user-friendliness. Of course, Hielscher ultrasonicators are CE compliant and meet the requirements of UL, CSA and RoHs.