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Home , Mold

6/15/2016

CDR UW Let’s Talk and

Mark E. Johnson Wisconsin Center for Dairy Research

Center for Dairy Research “Solution Based Research Backed by Experience, Passion and Tradition”

CDR UW What are Yeasts and Molds?

Bacteria (binary fission)

Yeasts (multiply by budding)

Molds (produce )

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Yeasts on (not crystals)

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Moldy cheese: Notice free serum

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CDR UW Washed Rind : Yeasts

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CDR UW What do you do about yeasts and molds? • Reactive approach: – We see molds/taste yeasty products – Now its time for action – Find the source – Major cleaning/ sanitation effort • Proactive approach: – We know that yeasts and molds are in our facility – We do all the right things to make sure that their numbers are controlled/eliminated – Monitor their numbers in the places that they might call home

CDR Requirements for Growth: yeasts and molds UW

• Water (but very much less than ) • Temperature (can grow under ) • Oxygen for molds (~1-2 %) • Oxygen +/– for yeasts • Acid, salt and low pH tolerant • Nutrition : not much for molds • Yeasts require

courtesy of Copyright Dennis Kunkel Microscopy

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CDR UW Water activity of various cheeses (1)

Cheese aw Brie 0.980 0.982 Cheddar 0.950 Cottage cheese 0.988 Gouda 0.950 Gorgonzola 0.970 Parmesan 0.917

(1) Ruegg, M. and Blanc, B, 1981. In “Water Activity: Influences on Food Quality”, ed. Rockland and Stewart, Academic Press, 799.

CDR UW aw Growth Limits (water = 1.0)

E. coli 0.96

C. botulinum 0.93

L. monocytogenes 0.91

S. aureus 0.86

Yeasts and molds 0.65-0.7

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CDR UW Sources of Yeasts and Molds • : major source is air-borne spores – From packaging material (damp boxes) – Moldy cheese – Anticaking agent (potato ) – Moldy vegetables – Condensate water on air-conditioning units, pipes, walls, floors, underneath equipment • Yeasts: major source is organic material – Vegetables, spices – Brine tank (people, contaminated cheese) – Residual product on equipment (biofilms)

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CDR UW & Mold Monitoring Program

• Air exposure plates weekly • Surface swabs • Brines sampled weekly

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CDR CDR Air and Brine Specification: UW Call for action

• Air: Yeast and mold > 10 cfu on exposed plate – Plate is exposed for 15 minutes • Brine: Yeast and mold >50 cfu/ml

CDR UW Typical Cheese Specification

• – negative • Coliform – <10/g- <100/g (some 10,000/g) • E. coli – negative • Yeast and Mold – <100/g (some plants <10/g)

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CDR UW Channel Brine System

CDR UW Impact of Brine Nanofiltration

Conventional Nanofiltration Filtration System System Salinity 90-100% 90-100% Molds 50-500/ml <10/ml Yeast 100-1000/ml <10/ml Std. Plate Count 25,000- <100/ml 100,000/ml Psychrotrophs 1000-2000/ml <100/ml Susp. Solids 5,000-20,000 mg/l <500mg/l

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CDR UW that do not survive • Coliforms • Pseudomonas • Pathogens • Vegetative cells of formers • Lactococcus • Yeasts • Molds

CDR Elimination of Spores UW  Air filtration • MERV 13 filters: Holds back particles 1-0.3 um -Minimum Efficiency Reporting Value - established by the American Society of Heating, Refrigeration and Engineers (ASHRAE) • Removes ~ 75 % of particles 1-0.3 um -This is not a true HEPA filter which is too impractical for dairy plants - High-Efficiency Particulate Arrestance (99.97 % removal of particles 0.3 um)

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• Traditional cleaning agents used by the food industry (chlorine, CDR UW hydrogen peroxide, iodine) are ineffective in destroying mold spores. • Cleaning with ozone is probably the best method of eliminating food spores in food processing plants. • Ozone is more than 3000 times more powerful a than chlorine and it is particularly helpful in destroying mold spores by virtue of its high redox potential. • Ozone is used in Japan, Europe and Australia, but has been used with limitation in the US. • Ozone can be used to clean air or to be incorporated in water (known as ozone charged water and used to clean pipes, tanks, floors , equipment, surfaces, walls, etc.

CDR UW What action do we take? – Positive air flow • Air treatment with ozone – Elimination of moist-humid areas – Removal of visible mold and all contaminated materials – In product use of mold inhibitors : sorbates, propionates, natamycin – Modified atmosphere packaging

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Checking for gas composition

For shreds, soft cheeses: 30-40 % CO2/60-70 % N

When mold occurs Bad sealing bars Poor package seals Poor gas blends (more than 0.5-1 % O2) Leakers

CDR UW Checking for Leakers

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CDR UW Final Recommendations •Food Plants who “deep clean” equipment as opposed to clean have less micro issues •In general, facilities where the ceilings in most areas are of a cleanable material and appear to be maintained and in good repair have less issues •Food Plants where the walls and floors have cracks, seams and holes, and when the equipment, contains rust and nothing gets done for a prolonged period have issues. •Food Plants where the cooling units are broken down regularly and cleaned have less problems. • Facilities where the overhead structures (such as lights) are made accessible for cleaning and sanitation have less issues

Bob Hendershot

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CDR UW Summary • Take a Proactive Approach • Sanitation and GMPs are key • Must be ever vigilant

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CDR UW Enumeration of Yeasts and Molds

• Dichloran-Rose Bengal-Chloramphenicol (DRBC) Agar – Suitable for all dairy products especially to inhibit spreading of mold colonies such as and – May give lower count on yeasts than yeast-extract-glucose- chloramphenicol agar (IDF recommended medium for yeasts) • 3M Petrifilm Yeast and Mold Count (dry rehydratable film) – Yeast appear as blue-green, off-white, small and more defined, sharp edges colonies – Molds are more diffuse and take on color of “natural” pigmentation • DO not invert plates-count plates with 15-150 colonies (25 C aerobic conditions for 5 days)

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