High pressure carbon dioxide treatment for fresh-cut carrot slices

The effects of high pressure carbon dioxide (HPCD) treatment on natural microorganisms, indigenous enzyme activity, damage to cell membranes and hardness in fresh-cut carrot slices were investigated. 1.86 log10 cycle reduction for aerobic bacteria (AB) and 1.25 for yeasts and molds (Y&M) were achieved at 5 MPa and 20 °C for 20 min. The residual activity (RA) of peroxidase (POD), polyphenol oxidase (PPO), and pectinmethylesterase (PME) exhibited initially increase and secondly decrease with treatment time and their minimum activity was 75.8%, 90.9% and 52.8% at 5 MPa and 20 C for 15 min, respectively. Membrane damage was evaluated by relative electrolyte leakage (REL) and malondialdehyde (MDA) content. HPCD caused a significant increase of REL in carrot slices and the REL of carrot slices treated at 5 MPa and 20 °C for 15 min was 5.7 times as much as that of the untreated, however, HPCD showed no effect on MDA content. The hardness was well retained after HPCD treatment and the largest loss was 7.9% at 5 MPa and 20 °C for 15 min.Industrial relevanceFresh-cut carrot slices are one of the most widely used products in prepared salads, and it required strict treatment conditions to protect its quality, especially to prevent microbial spoilage and enzymatic discoloration. HPCD is one promising novel non-thermal technique without compromising the flavor, taste and nutrition aspect of food. This study analyzed the effectiveness of HPCD as a method of preserving fresh-cut carrot slices, including inactivating natural microorganisms and enzymes which are crucial to quality control. Available data provided in this study will benefit the fresh-cut fruits and vegetables industry.

Research Highlights
► HPCD was firstly studied in the processing of fresh-cut fruits and vegetables.
► REL was a better indicator of damage to cell membrane than MDA in HPCD treatment.
► HPCD significantly inactivated AB, Y&M, POD and PME in carrot slices.
► HPCD can keep the hardness of carrot slices.
► HPCD can be a pretreatment in fresh-cut fruits and vegetables processing.