Josh Warren, Mary Angela Daum, and Michael J. Miller

Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign

Hard ciders, like other fermented beverages, may be contaminated by a variety of lactic acid bacteria (LAB). Bacteria can impart unwanted flavor qualities and foul production equipment. A successful antimicrobial for cider must control a variety of contaminants and be allowable under the applicable regulations. Hen egg white lysozyme and nisin have been used to target LAB in different applications. Lysozyme is approved for use in wine. Nisin has GRAS status for some food products. To our knowledge, applications of lysozyme and nisin in fermented ciders have yet to be examined in the literature. Initial efficacy was determined by applying different concentrations of the antimicrobials to agar plates of more than 14 different LAB frequently found as fermentation contaminants. A smaller subset of LAB was used in fermented and bottled cider for this project to evaluate the impact of nisin and lysozyme in bottled cider. This smaller group was selected based on the enzyme sensitivity data, growth in cider, and the literature. During mock contaminations, apple cider was racked from the primary fermentation and priming sugar was added. Samples contaminated with LAB were dosed with lysozyme and/or nisin at the bottling stage. Two weeks after bottling, cider samples were taken and LAB were enumerated using MPN with cycloheximide MRS media. Drop plate assay data revealed 9 of the 14 strains tested were insensitive to lysozyme to all concentrations tested (0 to 10000 µg/ml) while the most sensitive strain was inhibited at 40 µg/ml. Nisin consistently reduced colony formation of all LAB at concentrations ranging from 4 to 16 µg/ml, well below the maximum allowed in cheese (250 µg/ml). Mock contamination results revealed lysozyme and/or nisin treated ciders obtained up to a 3 log reduction in MPN/ml regardless of the source of contamination. Untreated samples ranged from 106 to 108 MPN/ml while the treated samples were 102 to 103 MPN/ml. These results suggest that nisin and lysozyme can effectively control cider contamination, giving the cider industry alternatives to traditionally used sulfites. With continued success in alcoholic beverages, consideration should be given to applying for GRAS status for nisin.