Master Food Preserver Slides · – Suspension of PVC particles in a liquid plasticizer – When heated, the two components melt together – Upon cooling, they solidify and form

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

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1850’s


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*

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4

1824

WWI 1914-1918

1850’s

1926WWII 1939-1945

1970’s

Present

1946*“Back up the cannon with the canner”

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5

1824

WWI 1914-1918

1850’s

1926WWII 1939-1945

1970’s

Present

1946*

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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.


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1824

WWI 1914-1918

1850’s

1926WWII 1939-1945

1970’s

Present

1946*

pressure canner

Glass lids to save steel

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WWII Victory Gardens Community canneries8


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- 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*

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0102030405060708090

1950-59 1960-69 1970-1979 1980-1989 1990-1996

# O

utbr

eaks

Home Processed Commercially processed Unknown


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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

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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

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California statistics

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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

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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

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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


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

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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


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

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Tomatoes – no liquid added (whole or halved)

Raw Quart or Pint

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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.”

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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.”

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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.”

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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

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NCHFP Does NOT

• Approve processes• Approve equipment• Recipes• Books

• They DO• Provide guidance on home canning that is

grounded in science

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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

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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

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• 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)

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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

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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

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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

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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

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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

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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

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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

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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

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Documents

Master Food Preserver Slides · – Suspension of PVC particles in a liquid plasticizer – When heated, the two components melt together – Upon cooling, they solidify and form