title: Incorporation of preservatives in polylactic acid films for inactivating Escherichia coli O157:H7 and extending microbiological shelf life of strawberry puree.
abstract: Antimicrobial films of polylactic acid polymer incorporated with nisin, EDTA, sodium benzoate (SB), potassium sorbate (PS), and their combinations were developed, and their antimicrobial effects on the inactivation of Escherichia coli O157:H7 and natural background microflora (total aerobic bacteria, molds, and yeasts) in strawberry puree at 10 and 22 degrees C were determined. Direct addition of SB+PS to strawberry puree was also used as a comparison with SB+PS film treatment. The combination treatment reduced the cell populations of E. coli O157:H7 from 3.5 log CFU/ml to undetectable levels (<1 CFU/ml) after 14 days and 1 day at 10 and 22 degrees C, respectively, while the cells of E. coli O157:H7 in control samples survived up to 48 days at 10 degrees C and more than 14 days at 22 degrees C. The SB+PS film treatment produced a greater reduction of population of E. coli O157:H7 cells than did the SB+PS direct addition treatment. Similar results were observed for inactivation of natural microflora. In general, the antimicrobial effect was in the following order: film combination > SB+PS film > SB+PS direct addition > EDTA film > nisin film. The data obtained in this study suggest two approaches toward the development of control interventions against E. coli O157:H7 and extension of the microbiological shelf life of strawberry puree: (i) using antimicrobial packaging and (ii) using combinations of preservatives. The film formulas developed here can be used to make bottles or as coatings on the surface of bottles for use in liquid food packaging.
authors.affiliation: Food Safety Intervention Technologies Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA. tony.jin@ars.usda.gov
authors.forename: Tony
authors.initials: T
authors.lastname: Jin
authors.forename: Howard
authors.initials: H
authors.lastname: Zhang
authors.forename: Glenn
authors.initials: G
authors.lastname: Boyd
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms; D001704:Biopolymers / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004357:Drug Synergism; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D005516:Food Microbiology; D018857:Food Packaging / Q000379:methods; D005519:Food Preservation / Q000379:methods*; D005520:Food Preservatives / Q000494:pharmacology*; D031985:Fragaria / Q000382:microbiology*; D006801:Humans; D009561:Nisin / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D001704:Biopolymers; D004338:Drug Combinations; D005520:Food Preservatives; D009561:Nisin