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Antimicrobial Effect of Haskapberry Juice and Extracts on Listeria innocua and E. coli.

Ban, Z., L. Fan*, W. Kalt, M. Vinqvist-Tymchuk, T. Hughes, C. Doucette and J. Guan. 2016. Antimicrobial Effect of Haskapberry Juice and Extracts on Listeria innocua and E. coli. Poster presentation at the United Fresh 2016 and S-294. June 10-14th, Chicago, USA.

Abstract

Haskap berries are the one of the rising stars of berry fruits in the Canadian marketplace. They can be used in the same way as other berries including fresh eating, jams and preserves, baking and juice. Research reports have shown that haskap berries have high levels of anti-oxidants, vitamin C and A along with high fibre and potassium. In our study, haskap berry juice, fractions including whole fruit extracts (EXT), sugars/acids (S/A), total phenolics (TP), total flavonoids (TF), and chlorogenic acid (CA) as well as a range of pure phenolic acids were investigated for their antimicrobial effects against Listeria innocua and E. coli. Antimicrobial properties of different concentration of haskap berry juice and extracts were determined based on the OD values and bacterial growth curves generated using Bioscreen C. Live/dead BacLight bacterial viability kits were used for quantitative assays of bacterial cell damage tested with fluorescence microplate reader. This assay utilized the SYTO 9 and propidium iodide (PI) stains. When used alone, the SYTO 9 labelled all bacterial cells, while PI worked only on bacteria with damaged membranes, causing a reduction in the SYTO 9 stain fluorescence when both stains were present. Haskap berry fractions on the membrane permeability and survival of L. innocua and E. coli were determined and relative fluorescence units (RFU) were used to express the degree of cell damage. Our results indicated that TP, TF and CA played an important role in damaging cell membrane of L. innocua while TP and CA also damaged cell membrane of E. coli. Phenolic acids from haskap berry including salicylic acid, caffeic acid, m-coumaric acid, and ferulic acid were found to have strong antimicrobial effects with minimum inhibitory concentrations (MICs) ranging from 2.5-5.0 mg/mL. The antimicrobial effects of haskap berry fractions such as anthocyanins (ACN), heteropolymers (HET) and proanthocyandins (PAC) on food pathogens have been testing in our lab.

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