Dual effectiveness of ascorbic acid and ethanol combined treatment to inhibit browning and inactivate pathogens on fresh-cut apples

Authors: YAN, SHOULEI - HUAZHONG AGRICULTURAL UNIVERSITY; Luo, Yaguang - Sunny; Zhou, Bin; INGRAM, DAVID - U.S. FOOD & DRUG ADMINISTRATION (FDA)

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2017
Publication Date: 2/16/2017
Citation: Yan, S., Luo, Y., Zhou, B., Ingram, D. 2017. Dual effectiveness of ascorbic acid and ethanol combined treatment to inhibit browning and inactivate pathogens on fresh-cut apples. LWT - Food Science and Technology. 80:311-320.

Interpretive Summary: Enzymatic browning is the most important factor that affects the quality of fresh-cut apple slices. However, the leading commercial anti-browning treatments are not compatible with the prevalent sanitizing agents. Commercially-produced apple wedges have recently been associated with several recalls due to foodborne pathogen contamination. New technologies are critically needed in order to simultaneously control cut-surface browning and human pathogen growth. This study evaluated the combined treatment of ethanol and ascorbic acid for its effects on both the inhibition of browning and inactivation of pathogens on apple wedges. Results showed that this treatment combination was able to successfully inhibit browning and growth of aerobic bacteria, and yeast and mold during storage, in addition to inactivating the human pathogens, Escherichia coli O157:H7 and Listeria monocytogenes on fresh-cut apple. The dual effects of ascorbic acid plus ethanol treatment to simultaneously control browning and microbial growth on apple slices suggest that this combined treatment has the potential to be adopted commercially to enhance both quality and safety of fresh-cut apples. This research benefits fresh-cut produce industry.

Technical Abstract: Commercially-produced apple wedges have recently been associated with several recalls due to foodborne pathogen contamination. The fresh-cut industry faces a major technical challenge due to the incompatibility between chemicals used to control spoilage and pathogenic microorganisms (usually oxidizers) and those used to control browning reaction (usually reducing agents). New technologies are critically needed in order to simultaneously control cut-surface browning and pathogen growth. This study evaluated the effect of moderate concentrations of ethanol in combination with ascorbic acid on the inhibition of browning and inactivation of pathogens on apple wedges. Apples (cv. Granny Smith) were cut into wedges, dipped in treatment combinations containing 1% ascorbic acid and 10%-40% ethanol, followed by dewatering, packaging (gas permeable film bags), and storage (1.5°C). Product quality was evaluated on days 0, 1, 4, 5, 7, 10 and 14. In parallel experiments, apple wedges were dip-inoculated with Escherichia coli O157:H7 and Listeria monocytogenes. The surviving E. coli and Listeria populations on samples were enumerated via selective media on days 0, 3, 7, 10 and 14. Results indicate that the combinations containing 30% ethanol significantly reduced L. monocytogenes populations immediately after treatment and further during cold storage. These treatment combinations also inhibited the growth of aerobic bacteria, and yeast and mold during storage. Treatment with the combination of 1% ascorbic acid and 30% ethanol also effectively inhibited browning reaction on the cut surfaces, and maintained the quality of apple wedges throughout cold-chain storage. However, treatments containing more than 40% ethanol caused unacceptable softening of the apple tissue. The dual effects of optimized ascorbic acid plus ethanol treatment to simultaneously control browning and inactivate pathogens on apple slices indicate that this combined treatment could be used to enhance both quality and safety of fresh-cut apples.