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Linda J. Harris, Ph.D.Specialist in Cooperative Extension
Sheryl Yamamoto, M.S.
Master Food Preserver SlidesOctober 9, 2014
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Table of Contents
Fermentation Microbiology:
Canning: Processes, Equipment and Supplies
Spoilage Microbiology
Milestones to Safe Home Canning
2
1850’s
Milestones to Safe Home Canning
Appert (1749-1841), a French chef from Napoleon’s time, developed the method for preserving food by sealing it in a jar.
Canning popularized: Advertisements in mainstream magazines.
1850’s
1824
1970’s
Present
WWI 1914-1918
1926WWII 1939-19451946*
3
Milestones to Safe Home Canning
4
1824
WWI 1914-1918
1850’s
1926WWII 1939-1945
1970’s
Present
1946*“Back up the cannon with the canner”
4
Milestones to Safe Home Canning
5
1824
WWI 1914-1918
1850’s
1926WWII 1939-1945
1970’s
Present
1946*
5
Milestones to Safe Home Canning
6
1824
WWI 1914-1918
1850’s
1926WWII 1939-1945
1970’s
Present
1946*
“…the department recommends the canning of [low-acid] vegetables with the steam-pressure canner.”
Pressure canners a) 5-20 lbs. b) 20-30 lbs, Both available in various sizes, up to 500 cans/day.
a. b.
Milestones to Safe Home Canning
7
1824
WWI 1914-1918
1850’s
1926WWII 1939-1945
1970’s
Present
1946*
pressure canner
Glass lids to save steel
7
WWII Victory Gardens Community canneries8
Milestones to Safe Home Canning
9
- 1970’s-early 80’s revival in home canning
- Corresponding increase in Clostridium botulinum cases due to improper canning
1824
WWI 1914-1918
1850’s
1926WWII 1939-1945
1970’s
Present
1946*
9
0102030405060708090
1950-59 1960-69 1970-1979 1980-1989 1990-1996
# O
utbr
eaks
Home Processed Commercially processed Unknown
Milestones to Safe Home Canning
10
1824
WWI 1914-1918
1850’s
1926WWII 1939-1945
1970’s
Present
1946*
Foodborne botulism outbreaks, 1950-19962.5 cases/outbreak average
Data from www.cdc.gov/ncidod/dbmd/diseaseinfo/files/botulism.pdf
87% of outbreakshome processed
10
Clostridium botulinum outbreaks in Home Canned Foods, US, 1998-2012
vegetables49%
meat/soup/stew20%
fish10%
unknown10%
tomatoes5%
mushrooms3%
garlic infused oil
3%
Outbreaks = 39Cases = 56Deaths = 7Unknown outcome = 2
11
California statistics
12
46
Foodborne outbreaks of botulism by state1950-1996 www.cdc.gov/ncidod/dbmd/diseaseinfo/files/botulism.pdf 13
California botulism home source
• 2000, canned tomato and squash, 2 cases• 2005, canned salmon, 2 cases 1 death• 2006, fermented tofu, male 75, female 67• 2006, canned carrots, male, 74, female 73• 2008, canned tuna, male, 52• 2008, home cured olives, female, 51• 2008, canned green beans, male, 68• 2009, canned tuna, male, 85, female 91• 2009, canned soup, female, 91• 2009, canned corn, male, 68 (died)• 2010, canned tuna, male, 47• 2011, canned corn, male, 60• 2012, canned tuna, female, 48
Male
Female
Average age: 68Median age: 68
CDC databases, 2000 - 2012 14
Pruno: C. botulinum hazardCalifornia 2004 5 cases
• Place ingredients in a plastic bag• Smash ingredients to a pulp• Place in a warm location and
allow to ferment for several days• Alcohol produced
Recipe can be found on Huffington Post: Jailhouse Wine
yeast
15
California botulism 2014
• 2 cases botulism in Ohio– Women in their 20s– Hospitalized and on ventilators
• Unlicensed facility– Inadequate process– Inadequate label– Sold farm stand and via internet
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Canning Research
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• Acknowledgement of wide range of pH in tomatoes that are canned– Recommendations for addition of acid
• Citric acid, lemon juice, vinegar
– Goal is <pH 4.3• pH target used by commercial canners• Prevents the growth of spoilage organisms
– Bacillus coagulans– Causes “flat-sour” spoilage
Research funding 1970s and 80s
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• Can be done a number of ways– Measuring temperature during process– Requires understanding of “lethality”
of target organism in food of interest• Two measurements• D-value “decimal reduction time” or time at a given
temperature, T, for a survivor curve to traverse one log cycle or equivalently, to reduce a microbial population by 90%, t = DT(log No - log N)
• z-value: Number of degrees of temperature required for the thermal death time curve to traverse one log cycle
Re-evaluation of processes
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• Challenge studies or “inoculated pack” studies– Clostridium sporogenes PA 3679
• Surrogate for C. botulinum
– Spoilage organisms of greater heat resistance
• Commercial process for low-acid foods determined by Process Authorities
Target organism
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Decimal Reduction Time (D-value)
Time
SurvivorsLog CFU/g
Decimal Reduction TimeTIME to reduce population by
90% or 1 log cycle
at specified temperaturein specified medium
1 log
D-value
D-value - Influence of temperature
Time
SurvivorsLog CFU/g
T1T2T3
As temperature increasesD-value decreases
Target level
z-value allows calculation of D value at temperatures not actually measured
Temperature
LogD-value
z-value is the temperaturefor 1-log decrease in D-value
A z is approximately 18 F°
1 log
z-value
• Montville et al., 1983. Inherent variability in the efficacy of the USDA raw-pack process for home-canned tomatoes. J. Food Science 48:1591-1597.– Eastern Regional Research Center USDA-Agricultural
Research Service– Built on earlier research same group– Bacillus licheniformis –
• demonstrated spoilage in canned tomatoes, elevates pH • noted lethality was dependent on canner size• determined thermal death characteristics in tomatoes
Evaluating tomato processes
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Variables which affect heat transfer in a boiling waterbath canner
T = temperature cs = cold spotc = specific heat wb = water bathm = mass w = water
t = tomatoes
thermocouple
25
Raw pack tomatoes, 35 min process
Variable LARGE SMALL SAUCEPAN
# Jars 8 6 1Water (L) 18 12 3Come up time (min) 18-25 9-10 0Total process time (min)* 120-150 115-134 100Max T°F cold spot 199-206 194-196 181
Water (L) required to cover top of jar w/ 1 ½ inches of waterInitial Tcs – Before adding to the waterbath = 19°CCome up time = time required for water to resume boiling*Total process time (min) = come up time + 35 min + cooling time (t=60°C)
Montville et al., 1983 26
Calculated lethality
Conditions 35 min process 45 min processLarge canner, 8 jars 4.5 to 7.4 5.1 to 9.9Large canner, 4 jars 3.1 6.3Small canner, 6 jars 2.7 to 3.2 5.6Small canner, 3 jars 2.5 3.3
Calculated lethality for B. licheniformis spores number of log reductions
Montville et al., 1983 27
Summary/Recommendations
• The cool down period – 63 to 77% of lethality
• Length of come-up time – correlated to total lethality
• Variables such as heat source, ambient temperature influence lethality
• The process is inherently variable– Errors in the home would add to this variability
Montville et al., 1983
Pressure CanningCool-down period
18 to 50%of lethality
28
Summary/Recommendations
• “The generation of process recommendations based on every canner, load size, and water level combination would be a cumbersome, confusing, and costly endeavor that would create chaos in the canning community.”
• Until issues resolved recommend – raw pack not be used
• Recommend hot pack– 35 min for pints and 45 min for quarts
Montville et al., 1983 29
Canning tomatoesBoiling water canner, 0-1000 ft elevation
• Processes are simplified and account for variability. • Based upon worst case scenario.
Type Style of Pack
Size Process Time
Tomato juice Hot Quart 40Tomato sauce (thick or thin) Hot Quart 40Tomatoes in water (whole or halved) Hot and
RawQuart 45
Tomatoes in tomato juice (whole or halved)
Hot and Raw
Quart or Pint
85
Tomatoes – no liquid added (whole or halved)
Raw Quart or Pint
85
NCHFP current recommendations 30
What is the NCHFP?
• National Center for Home Food Preservation– Funded entirely by grants – NOT guaranteed
• 2000-2004– Research to develop recommendations for new
products – Microbial challenge studies of some historical
processes to validate their safety in light of newer food safety knowledge.”
– Research on microwave blanching of vegetables.”
31
NCHFP Research
• 2005-2010– “…laboratory research on a partially-fermented,
refrigerator-stored dill pickle procedure to describe any potential heating treatments for Listeria risk.”
– “…applied laboratory research on a home-canned tomato-based salsa procedure.”
32
NCHFP Research
• 2005-2010– “…laboratory research on a partially-fermented,
refrigerator-stored dill pickle procedure to describe any potential heating treatments for Listeria risk.”
– “…applied laboratory research on a home-canned tomato-based salsa procedure.”
33
NCHFP Research
• Current 2010-2014 (2015) research projects include– “…laboratory research to compare home canning
lid systems on features of sealing rates and vacuums obtained.”
– “…laboratory research on atmospheric steam canning for acid foods”
– Curriculum for youth
34
35
NCHFP Does NOT
• Approve processes• Approve equipment• Recipes• Books
• They DO• Provide guidance on home canning that is
grounded in science
36
NCHFP Canning Processes
• Developed using the following:– Stovetop pressure canner (4 1-quart jars)– Waterbath canner– Two piece lids with Plastisol or rubber liner
• Processes that have not been evaluated and therefore not explicitly recommended:– Electric pressure canner– One piece lids: lug or continuous thread– Atmospheric steam canning
37
Small Pressure CookersFeatured as a “Burning Issue” (Nov 7, 2006)
• Less metal, smaller diameter, less water• Heat up/cool down times are shorter• Total processing heat reduced• Safe methods developed using a standard
pressure 4-qt jar canner• No recommended processes for canning in a
small pressure cooker
38
• One manufacturer states their unit can be used for canning low acid foods, however, there have been no scientific studies to show that the process is safe.
• Short come up and cool down times– manufacturer states 10-15 min come-up time and a
10-15 minute cool down time• Cooker reaches 240°F, however the total process
time is shortened• Scientific studies needed
Electric Pressure Cookers/Canners
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Types of lids
Weck jarsReusable lid
Tattler lid and gasket
Conventional 2-piece lid w/ plastisol
1 Piece lidw/ plastisol
1 Piece lug lidw/ plastisol
Bale style jars 1 Piece lid, no buttonw/ plastisol
Plastic storage cap (not for canning)
40
What is Plastisol??
• Creates vacuum seal for canned goods– Suspension of PVC particles in a liquid plasticizer – When heated, the two components melt together– Upon cooling, they solidify and form a seal
• Plastisol for different temperature applications– Match the liner to the application. – High heat could distort a low heat liner = failed seal.– Consult with manufacturer to determine the correct
lid for your application
Plastisol
41
One Piece Canning Lids
• Currently being evaluated by NCHFP? (see slide #12, 2010-14 NCHFP projects)
• Manufacturers state one piece lids can be used for home canning
• But…Different lids for low heat (waterbath) vs. high heat (pressure) canning (see slide on plastisol)
• Some discussion about which is best• Potential for higher seal failure
42
Case Study: Thermophilic spoilage
• Low sugar recipe• Stored in sunlight• Possible issues:
• Inadequate acid (apricots can be as high as pH 4.8!)
• Inadequate heat process• Presence of thermophilic
sporeformers• Gas production Foam
43
Sauerkraut fermentation• Shredded cabbage + 2.25% salt + 68°F temperature • Leuconostoc mesenteroides (1-3 d): heterofermentation – C02, ethanol, lactic acid, • CO2 replaces oxygen anaerobic environment
– Lactic acid 0.25 to 0.3% and pH drops to below 4.0• Lactobacillus plantarum (weeks): homofermentation – lactic acid
– Lactic acid 1.5-2% and pH drops below 3.8 to 3.5• Lactobacillus brevis (weeks): homofermentation – lactic acid
– Lactic acid 2-2.5%• Fermentation finished in several weeks
44
Cashew cheeseSalmonella Stanley• Lots of on-line recipes• Commercial outbreak with
unlicensed facility– Cashews mixed with water and
“starter culture”– Held at room temperature for ?– Blended, ingredients added to
multiple flavors• 17 illnesses, 3 states
45
Yeast growth on sauerkraut
• Presence of oxygen = (enzymatic browning)
• Scum = yeast• Pinkish pigment from yeast
• Yeasts consume carbohydrates without acid production
• Increase C. botulinum risk 46
Botulism in fruits and olives
Fruit-Botulism Outbreaksapple sauce, apricot butter, apricotsFigs, pears, olives, pumpkin butter,
tomatoes
• Mold and yeast create favorable conditions for C. botulinum growth– Break down food– Raise pH (decreases acidity)
• Food showing appreciable mold growth or fermentation should be destroyed
• Fruit-related botulism outbreaks frequently associated with mold growth
47
Pickles: Scum and sediment
• White scum and sediment = aerobic yeast• Mold and yeast create favorable conditions for
C. botulinum growth– Break down food– Raise pH (decreases acidity)
• Yeast itself is harmless
48
Summary
• Home food preservation recommendations are:– Scientifically based– Account for inherent variability
• Raw materials• Equipment
• Establishing new processes for new “recipes” or new equipment is:– Challenging– Expensive– Funding is generally lacking
• We need MFPs to teach basics
49