Two-Step PEF Processing for Enhancing the Polyphenol Concentration and Decontaminating a Red Grape Juice.

Area of Science:

• Food Science and Technology
• Biotechnology
• Agricultural Science

Background:

• Traditional red grape juice processing often involves heat or enzymatic treatments, which can degrade beneficial compounds like polyphenols.
• Pulsed Electric Fields (PEF) technology offers a non-thermal processing alternative with potential for preserving or enhancing juice quality.

Purpose of the Study:

• To evaluate Pulsed Electric Fields (PEF) as a dual-action processing method for red grape juice.
• To enrich juice with polyphenols and achieve microbial decontamination.
• To assess the impact of PEF on juice quality, sensory characteristics, and microbial stability during storage.

Main Methods:

• Two-stage PEF treatment: first on grapes for polyphenol enrichment, then on extracted juice for microbial decontamination.
• Spectrophotometric measurements to quantify polyphenol content and color intensity.
• Microbiological analysis to determine microbial inactivation and stability (<30 CFU/mL).

Main Results:

• PEF treatment of grapes resulted in 1.5-fold higher polyphenol content and double the color intensity compared to control juices (p ≤ 0.05).
• Subsequent PEF decontamination (17.5 kV/cm, 173.6 kJ/kg) reduced microbiota (yeasts, moulds, bacteria) below detectable levels.
• PEF-treated juice remained microbially stable for 45 days, even at elevated storage temperatures (10 °C).
• Juice quality and sensory attributes were unaffected by PEF treatments or storage conditions.

Conclusions:

• PEF technology shows significant potential for producing polyphenol-enriched and microbially stabilized red grape juice.
• This method provides a sustainable and effective alternative to conventional enzymatic and heat treatments in the juice industry.
• PEF processing can enhance both the nutritional and shelf-life properties of red grape juice without compromising sensory quality.