Nut Handling and Processing for Confectioners and Small Nut Roasters

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Nut Handling and Processingfor Confectioners and
Small Nut Roasters

• Session 1 Microbiology of Nuts
• Dr. Michael Doyle, University of Georgia

Sponsored by
In partnership with
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Microbiology of Nuts
Microbiology of Nuts

• Michael Doyle

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Examples of Types of Microbes Potentially Found
on Nuts

• Bacteria
• Not likely harmful
• Pseudomonas
• E. coli
• Xanthomonas
• Clostridium
• Human pathogens
• Salmonella
• Enterohemorrhagic E. coli (e.g., E. coli O157H7)

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Examples of Types of Microbes Potentially Found
on Nuts

• Molds
• Aspergillus spp.
• Aspergillus flavus/parasiticus - Aflatoxin
• Penicillium spp.
• Fusarium spp.
• Eurotium spp.

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Sources of Microbial Contaminants

• Primary sources of salmonellae are intestinal
  tracts of animals (domestic and wild) and humans
  shed in feces
• Feces can contaminate soil and water (irrigation
  and processing)
• Salmonellae can survive in some soils for months
  to years in water for weeks to months
• Primary sources of Enterohemorrhagic E. coli
  (e.g., E. coli O157H7) are intestinal tract of
  ruminants (e.g., cattle, goats, sheep, deer)

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Sources of Microbial Contaminants

• Primary source of molds such as aspergilli and
  penicillia is soil not directly related to fecal
  contamination

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Peanuts

• Cultivation, Harvest, Storage

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Cultivation

• Seed is planted in April May
• Approximately 130 days from planting to
  harvesting
• Cultivated in Virginia, North South Carolina,
  Georgia, Florida, Alabama, Mississippi, Texas,
  Oklahoma, and New Mexico

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Harvesting

• Peanuts are harvested from Aug-Nov
• Peanuts are dug, inverted, and left in the field
  to partially dry for about 3 days before being
  combined which separates the vine from the
  inshell peanut

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Grading/Storage

• After the peanuts are combined, these farmer
  stock peanuts are taken to a local buying point
  for grading, drying, and storage until needed for
  shelling

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Storage

• Peanuts are stored in specially-designed farmers
  stock warehouses until shelled. The raw shelled
  peanuts are put in one ton tote bags and then go
  into cold storage warehouses until shipped to
  manufacturer

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Examples of Potential Sources of Pathogen
Contamination of Peanuts During Production

• Field fertilized with untreated manure or sewage
  as a soil amendment
• Salmonella can survive in soil for months or
  years
• Field irrigated with water contaminated with
  animal waste
• Untreated surface water (ponds, rivers) with
  runoff from livestock operations
• Wildlife grazing on or near fields

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Examples of Potential Sources of Pathogen
Contamination of Peanuts During Storage

• Leaks in roof on which birds congregate
• Rodent and insect activity, especially if
  facility is near livestock operations
• Forklift and transport equipment exposed to mud,
  water or contaminated soil outdoors brought into
  sheds and warehouses without prior cleaning and
  disinfection

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Examples of Potential Sources of Pathogen
Contamination of Tree Nuts in Orchards

• Cattle, livestock or wildlife grazing in orchards
  especially near trees
• Fertilizing soil in orchards with untreated fecal
  waste
• Shells of many tree nuts such as pecans are
  porous and can become contaminated by contact
  with soil
• Exposure to water (rain or processing) provides
  conditions for growth of salmonellae

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Essential Conditions for Microbial (Salmonella)
Growth

• Food/Nutrients
• Water/Moisture
• Temperature

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Characteristics of Human Pathogens That May be
Associated with Nuts

• Salmonella
• Can survive for months to years in low moisture
  foods such as nonfat dry milk, peanut butter,
  chocolate
• Small numbers of this bacterium can produce
  illness when consumed in high-fat foods such as
  chocolate (lt 1 Salmonella/g), peanut butter,
  cheese

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Characteristics of Human Pathogens That May be
Associated with Nuts

• Salmonella (Cont)
• Heat resistance increases with decreased moisture
  content/water activity
• Example
• 165F (instantaneous) kills gt 10,000,000 (gt7 log)
  Salmonella/g in ground beef, milk, poultry
• 194F for 50 min kills 100,000 (5 log)
  Salmonella/g in peanut butter
• 305F (oven dry heat) for 15 min kills 100,000 (5
  log) Salmonella/g on peanuts

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Characteristics of Human Pathogens That May be
Associated with Nuts

• Salmonella (Cont)
• Growth prevented by low moisture content
  (water activity lt 0.95)
• Growth typically prevented by temperature less
  than 5C (41F) or greater than 46C (115F)
• Optimum temperature for growth is 35 - 37C (95 -
  99F)

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Characteristics of Human Pathogens That May be
Associated with Nuts

• Enterohemorrhagic E. coli (E. coli O157H7)
• Can survive in soil and water for months
• Exceptional tolerance to acidic conditions
• Can persist in acidic foods for exceptionally
  long periods of time
• Have a low infectious dose (lt 100 cells)
• Cause severe symptoms in children

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Determination of Pathogen Contamination of Nuts
and Nut Products

• Requires a microbiological assay that has been
  specifically validated to detect the target
  pathogen (such as Salmonella) at a minimum level
  of sensitivity (e.g., 1 CFU/25 grams)
• Methods in the FDA Bacteriological Analytical
  Manual are the gold standard for detecting
  pathogen contamination in food products regulated
  by FDA (Dec 2007 edition)
• (http//www.foodsafety.gov/ebam/bam-5.html)

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Determination of Pathogen Contamination of Nuts
and Nut Products

• Methods validated to be equivalent to the FDA BAM
  protocols for detecting the target pathogen in
  specific products at the minimum level of
  sensitivity indicated by FDA, are acceptable
  alternatives

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Determination of Salmonella Contamination of Nut
Products by FDA BAM Protocol (Cultural Method)

• Preenrichment
• Add 25-gm sample to 225 ml trypticase soy broth,
  mix well and incubate for 24 2 h at 35C
• Selective enrichment
• Incubate 0.1-ml portion of preenrichment culture
  in Rappaport-Vassiliadis (RV) medium and
  tetrathionate broth, and incubate for 24 h 2 h
  at 42C

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Determination of Salmonella Contamination of Nut
Products by FDA BAM Protocol (Cont)

• Selective Isolation
• Plate onto bismuth sulfite (BS) agar, xylose
  lysine desoxycholate (XLD) agar, and Hektoen
  enteric (HE) agar, and incubate at 35C for 24
  2 h BS agar also for 48 h if no suspect colonies
  at 24 h
• Identification/Confirmation
• Streak suspect colonies onto MacConkey agar, HE
  agar or XLD agar, and incubate at 35C for 24 2
  h
• Biochemical and serological assays

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Rapid Detection of Salmonella Contamination of
Nuts and Nut Products

• Acceptable methods for rapidly detecting (lt 8
  hrs) Salmonella in nut products should soon
  (within 2 years) be available
• Based on shortened enrichment and molecular
  detection (e.g., Gen-Probe rRNA-based automated
  pathogen detection system) or Raman spectroscopy
  real-time (lt 5 min) assay

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Symptoms and Consequences of Salmonellosis

• Symptoms
• Fever, abdominal pain, diarrhea
• Chronic disease consequences
• Arthritis (Reiters syndrome)
• Onset time usually 12 - 72 hrs (can be a week)
• Duration of illness usually resolved within 5 -
  7 days
• Most susceptible populations generally made ill
  by lower infectious dose and experience more
  severe symptoms or death than general population

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Symptoms and Consequences of Enterohemorrhagic E.
coli (E. coli O157H7) Infection

• Symptoms
• Severe abdominal cramping (like appendicitis),
  bloody diarrhea (all blood, in stools), vomiting,
  kidney failure
• Onset time usually 3 - 4 days
• Duration of illness usually 5 - 7 days
• Most susceptible populations are children and
  elderly (5 - 10 of those diagnosed with EHEC
  infection) who develop renal failure (hemolytic
  uremic syndrome, HUS) which may require dialysis
  (can be permanent) and kidney transplant can
  lead to death

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Most Susceptible Populations to Salmonella

• Newborns, infants, the elderly and
  immunocompromised individuals are more
  susceptible to Salmonella infections than healthy
  adults
• Incompletely developed immune system in newborns
  or infants
• Weak or delayed immune response in the elderly
  and debilitated persons
• Low gastric acid production in infants and seniors

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High Fat Content of Food InfluencesInfectious
Dose

• High fat content is common factor among foods
  associated with low infectious dose (e.g., cocoa
  butter in chocolate, milkfat in cheese and nut
  butter in nut-containing foods)
• Suggested that entrapment of salmonellae within
  hydrophobic lipid micelles affords protection
  against the bactericidal action of gastric
  acidity
• Rapid emptying of fat-based gastric contents
  could also provide alternate mechanism

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Principles Used in Mitigating Risks of Pathogen
Contamination of Nuts

• Preventing contamination throughout the entire
  cycle, from production to mouth
• Applying control interventions from production to
  mouth
• Moisture, temperature, vermin controls
• Detection of pathogens and indicators of pathogen
  contamination by testing
• Chemical antimicrobials
• Thermal treatments
• Non-thermal physical treatments (e.g.,
  irradiation, high pressure)
• Responding rapidly to pathogen contamination and
  taking effective corrective action

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• The principles used in mitigating risks of
  pathogen
• contamination of foods (nuts) are applied by the
  food
• industry using a systems approach that includes
• Sanitation Standard Operating Procedures (SSOP)
• Current Good Manufacturing Practices (cGMP)
• Hazard Analysis Critical Control Point Systems
  (HACCP)

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HACCP for Nut and Nut Product Processors

• Thermal processing is a common treatment (CCP)
  employed by the nut industry for mitigating
  pathogenic bacterial hazards

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Theoretical Thermal Inactivation Curve for
Salmonella in Milk Chocolate at 160F (71C)
5 10 15 20
25 30
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Thermal Inactivation of Pathogens

• Thermal processes are designed to kill a minimum
  number of a target pathogen (e.g., Salmonella or
  E. coli O157H7)
• Heat ground beef to internal temperature of 160F
  to kill 100,000 (5 log) E. coli O157H7/g
• Heat canned foods to kill 12 log (12D) of
  Clostridium botulinum spores/g
• Heat poultry to internal temperature of 165F to
  kill 5 log Salmonella/g
• Heat almonds (peanuts) to kill at least 10,000 (4
  log) Salmonella/g

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• What Should Be the Targeted Log Reduction
• for Salmonella on Nuts/Nut Products to
• Ensure Safety?

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• Considering the high temperature and
• extended heating time needed to kill 5 log of
• Salmonella in peanut butter (49 min at 194F
• or 3.3 h at 170F), this is not likely a suitable
• treatment to render a product of acceptable
• quality.

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• Therefore, the key critical control point to
• ensure safety from Salmonella contamination
• from raw nuts in peanut butter/product
• manufacture is the whole nut roaster.

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• If the roaster conditions are designed to kill
• 100,000 (5 log) Salmonella/g, then the
• incoming load of Salmonella on peanuts
• must be less than 5 log or greater than 1
• Salmonella will be present per gram of
• peanuts.
• Areas of localized Salmonella growth,
• as occurs with A. flavus for aflatoxin
• production, can be a confounding factor.

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Conclusions

• Peanuts and tree nuts are now considered
  high-risk foods with regard to Salmonella
  contamination
• The low-moisture, high-fat content of nuts
  contributes to the
• High temperature, extended time required to kill
  Salmonella
• Lower infectious dose of Salmonella
• Long-term persistence of Salmonella in nut
  products

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Conclusions

• Mitigation of Salmonella contamination of nuts
  should be addressed from production to
  consumption.
• Nuts should be produced and stored under
  conditions to prevent Salmonella growth.
• The nut roaster is critical to ensuring the
  safety of nuts
• Temperature-time conditions for nut roasting must
  be validated to ensure efficacy in killing the
  targeted number of Salmonella.
• Roaster conditions, including nut bed depth and
  uniform loading, and accurate monitoring of
  temperatures and time, must be properly
  controlled.

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Questions?

• For QAs and Food Nut Safety Resource Guide
• http//www.ecandy.com/Content.aspx?ContentID7134