INHIBITION OF CLOSTRIDIUM BOTULINUM IN REDUCED-SODIUM PASTEURIZED PROCESS CHEESE PRODUCTS

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1 INHIBITION OF CLOSTRIDIUM BOTULINUM IN REDUCED-SODIUM PASTEURIZED PROCESS CHEESE PRODUCTS University of Wisconsin-Madison Kathleen Glass, Food Research Institute Acknowledgements: Funding DRI Laboratory Staff: Ming Mu, Subash Shrestha, Brandon Wanless, Max Golden Former staff: Russ McMinn, Lindsey McDonnell CDR Industry Team Research Forum November 10,

2 Pathogen Inhibition in Cheeses 2! Microbial control by water activity and ph! Natural Cheese! Competitive microflora! Starter, non-starter lactic acid bacteria! Pasteurized process cheese! Exclude vegetative microorganisms by heating/hot-fill! Spore forming bacteria survive! Added moisture, higher ph must be compensated by other formulation changes

3 Process Cheese safety FRI Model (aka Tanaka Model) 3 Safety factors for control of Clostridium botulinum in shelfstable process cheeses " Moisture " ph " Sodium chloride " Sodium phosphate " Salt and not sodium ion is antimicrobial Tanaka et al, 1986 JFP

4 Critical use of the FRI Model 4! Applicable to standard-of-identity process cheese spreads (21 CFR 133)! Full-fat (~18-22% fat)! >51% Cheddar cheese # Typically contains % lactate! Disodium phosphate emulsifier! Sodium-based salts

5 Unsafe ~320 mg/28 g Safety Line ~400 mg/28 g Safe Sodium reduction initiative School lunch program target mg/28 g (1 oz.) serving Tanaka et al, 1986 JFP

6 Other factors affecting safety Increase safety Decrease safety No effect or Unknown effect Low water activity High water activity Substituting cheese with other dairy solids Reduced fat High fat/high-moisture Substituting milkfat with vegetable fat Lactate (lactic acid or Na/ K lactate) Sorbate (sorbic acid or potassium sorbate) Nisin Certain polyphosphates Removal of lactate or other antimicrobial Substituting Na-salts with K-salts Small diameter, brined vegetable or dried, thin particulates 6

7 2015 Predictive Model for Process Cheese Safety 7! Builds on 1986 FRI/Tanaka Model! Adds:! Sodium reduction by substitution with potassium salts # Molar basis! Fat reduction! Sorbic acid as growth inhibitor

8 Experimental Design: 8! Central composite design with 7 parameters and 80 runs: Factor Test Variables Low Interm. High 1 % fat % moisture ph % K replacement* % sorbic acid % NaCl equivalent % DSP solids equiv total salts mg Na / 100 g mg Na if 50% replacement ! *K replacement on molar basis! Model predictions are valid for factor level combinations within these ranges only! Combinations chosen such that >50% samples were toxic

9 Experimental Design (cont.) 9! Non-standard process cheese (15% cheese)! 3-log proteolytic C. botulinum spores per gram! Cooked to 175 F/79 C, 5 minutes! Hot-filled into sterile vials! Anaerobic, 80 F (27 C)! Five samples/variable assayed at:! 0, 1, 2, 3, 4, 8.5, 17.5, 26, 40 (+56) weeks! mouse bioassay; odor/appearance! Proximate analysis and MPN spore enumeration to confirm targets! Parametric survival model was fit to the censored time-to-toxin data.

10 Factor Effect Importance Ranked by of 10 Likelihood Ratio Chi-square $ All linear and quadratic (curvilinear) and pairwise effects were considered for model fit. The significant effects are: Effect ChiSquare Prob>ChiSq ph <.0001 % sorbic acid <.0001 moisture <.0001 DSP*DSP <.0001 NaCl eqv <.0001 DSP <.0001 ph*% sorbic acid <.0001 moisture*% sorbic acid <.0001 NaCl eqv*% sorbic acid moisture*fat fat moisture*nacl eqv moisture*ph %K replacement

11 Effect of salt/sodium reduction 11 total salts (including emulsifier) est sodium mg/ 28 g total salts (including emulsifier) Predicted Fail time in Weeks est sodium mg/ Predicted Fail 28 g time in Weeks Ex. Non-standard product, 50% moisture, ph 5.4, 10% fat; low lactate levels, no sorbate %K replacement

12 Effect of sorbic acid addition 12 total salts (including emulsifier) Predicted Fail time in Weeks est sodium mg/ 28 g % sorbic acid Note: model needs further validation Use for guidance only for product developers Ex. 50% moisture, ph 5.4, 10% fat

13 Conclusions 13! Shorter time to toxin production in 2015 model samples! May be due to low lactate levels in low cheese system (not modeled)! 0.2% sorbate very significant effect! Substituting Na salts with K salts on a molar basis can be done without any negative impact on safety! DSP levels constrictive for typical production! DSP least effective at 1.2% (most conservative use)! Setting probability to good representation for time to toxicity! Model in review; not for release yet! Additional study should be conducted to validate model

14 Acknowledgements 14! Co-Authors (significant contributions to production, testing and data analysis)! FRI: Ming Mu! Kraft Heinz Company: Frank Rossi, Brian LeVine! Technical assistance! FRI: Max Golden, Brandon Wanless, Russell McMinn, Subash Shrestha, Lindsey O Brien, Quinn Huibregtse, Emily Merry, and Shanna Sticka! Wisconsin Center for Dairy Research: Juan Romero! Kraft Heinz Company: Robert Carter! Food Safety Curves Task Force! Chair: Nigel Kirtley, Kraft Heinz Company! Coordinator: David McCoy, Dairy Research Inc.! This research was funded by contributions by members of the Food Safety Curves Task Force to Dairy Research Inc. and by unrestricted gifts to the Food Research Institute, University of Wisconsin-Madison! Sponsoring companies included ICL Food Specialties, Kraft Heinz Company, Great Lakes Foods, Schreiber Foods, Inc., and Land O Lakes.

15 Questions? Kathleen Glass