Module 7: Food safety
Food safety
Author: Dr Joseph Smilanick, Plant Pathologist, California
The risk of foodborne human microbial disease to consumers is a subject of increasing attention and
regulation throughout agriculture. Primarily an issue for food processors or for crops grown on the soil, this risk
is exceptionally low for table grape growers. In the United States, there are no threshold tolerances for human
pathogens in foods, so confirmed finds on foods can trigger recalls, public health press releases, product
seizure, facility shut down, facility de-registration, court-ordered legal actions, and even criminal prosecution.
Furthermore, demands by fastidious buyers are increasing worldwide and understanding compliance with
these increasing demands is a necessity. Sanitation and its monitoring and documentation are the most
important elements of compliance. For producers of table grapes, sanitation has other benefits, namely, a
reduction in postharvest pathogen populations that cause diseases that harm table grape storage and shelflife.
Food safety and table grapes
In the United States, Public law 111-353, the Food Safety Modernization Act (FSMA), was passed in 2011 and
stated the authority for the protection of consumers from risks of microbial diseases on foods to be wholly
under the jurisdiction of the Food and Drug Administration (FDA 2011). The development of regulations to
minimise risks of foodborne diseases on fresh products is currently under development, and once formulated
they will be phased in over a period of years.
Incidents of human disease (www.fda.gov/Food/default.htm) spread by whole fresh fruits is very rare. Table
grapes are a particularly low risk for contamination by the primary pathogens of concern (Salmonella spp.,
Echerichia coli, and Listeria monocytogenes). In California, where 99% of US table grapes are grown, most
are picked by hand into totes in the vineyard, hauled to the ends of the rows, and packed into their final
commercial package at open mobile work stations.
Alternatively, picking grapes into stackable totes for later cold storage, with final packing inside the (cold)
storage building, is an increasingly common practice. This is done primarily to comply with some buyers’
demands that table grapes and other fresh products be packed indoors and to facilitate the assembly of bicoloured and tri-coloured grapes into clamshell boxes (punnets).
The most demanding food safety regulations are directed at food processors. Risks of microbial contamination
increase with postharvest processing (de-stemmed single berry packs, peeled portion packs, salads, candy
coated products, cutting, juicing, macerating, crushing, etc.); these are not typically done under the grower’s
management and liability for the safety of these products lies with the processor, not the grower. Under the
developing FSMA rules, vineyard packing of table grape handling will likely not be classified as “processed”.
However, raisin growers and packagers of raisins may be classified as processors.
Microorganisms of greatest concern
A comprehensive review of microorganisms of concern of foods in available (without charge) and is highly
recommended (Food and Drug Administration 2012). The microorganisms of greatest concern on fresh
produce include:
Listeria monocytogenes. Found in the environment on decaying vegetation and many other locations.
Transient or resident within facilities, on packingline belts, dirty totes, sponges, brushes, etc. Growth continues
(slowly) to freezing temperatures. Onset of the human illness (listeriosis) it causes is slow, and can take up to
months. Many (>10,000) cells are required to cause illness, and typically the aged, very young, or immune
compromised people are at greatest risk.
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Food safety
Salmonella spp. Its presence indicates coliform contamination (soil amendments, water, animals, human
handlers). It is primarily an intestinal inhabitant of animals and grows at relatively warm temperatures (above
5.3°C). Primarily transient in field environments and on produce, but it can persist at very low levels for long
periods, especially if dry. Onset of human illness (non-typhoid salmonella) is rapid, within hours or a few days.
Even a few (1-10) cells can cause illness.
Echerichia coli. Its presence indicates coliform contamination (soil amendments, water, animals, human
handlers). It is primarily an intestinal inhabitant of animals, grow at relatively warm temperatures (above
6.5°C). Primarily transient in field environments and on produce, but it can persist at very low levels for long
periods. Multiple forms based on illness symptoms: enterotoxigenic, enteropathogenic, enterohemorrhagic
(O157:H7 in this class) and enteroinvasive. Onset of human illness can be rapid, or up to 9 days. Even a few
(1-10) cells can cause illness.
Table 1. Approximate total nitrogen removed by crops and typical N fertiliser rates.
Pathogen
Limiting conditions for pathogen growth
Min AW (using
salt)
Min pH
Max pH
Max %
water
phase
salt
Min
temp
(°F)
Max
temp
(°F)
Oxygen
requirement
10
6.5
43.7
120.9
facultative
anaerobe
Pathogenic
strains of
Escherichia coli
0.95
4
Listeria
monocytogenes
0.92
4.4
9.4
10
31.3
113
facultative
anaerobe
Salmonella spp.
0.94
3.7
9.5
8
41.1
115.22
facultative
anaerobe
*Table grape characteristics: water activity (AW) >0.98, pH 3.5 to 4.5, minimal salt content, storage
temperature -0.5 to 1.0°C.
Estimating risks
These aspects of table grape handling diminish risks:



Sulphur dioxide has potent antimicrobial activity. It’s used by conventional growers (as opposed to
organic growers, where its use is banned) during initial pre-cooling and subsequent weekly cold
storage fumigations, and in sulphur dioxide releasing generator pads and sulphur dioxide emitting
liners are placed within export packages;
Table grapes generally have a high quality cold chain that employs temperatures that slow or stop the
growth of many human pathogens;
Grapes are not subjected to postharvest wet processing, contact with packing or grading equipment,
and no postharvest fungicides or waxes are applied.
These aspects are associated with increased risk:

Grapes are a field grown product with bird and other animal contact possible;

Manual handling at harvest followed by a vineyard pack station to assemble packages entails risk of
contact with contaminated hands and surfaces; and

Table grapes are a product consumed raw without peeling or cooking.
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InnoGrape: Innovation in Table Grape Production
Food safety
Measures to manage risks have not been formally developed for the table grape industry (and many other
fresh products) at this time and are under development (FDA, 2013). Hazard analysis and risk-based
preventive controls typically require facilities to implement the following:




Evaluate hazards that could affect food safety;
Identify and implement preventive controls to prevent hazards;
Monitor controls and maintain monitoring records; and
Conduct verification activities.
Sanitation and monitoring
Once hazards are identified, it is likely worker training and sanitation measures will be needed. Sources of
contamination include soil amendments (compost, manures), agricultural water, domestic and wild animals,
soiled implements and vineyard harvest totes, and worker illness or poor hygiene.
The first step in sanitation is simple cleaning. Elements include power or pressure washing pick pans before
use, frequent hand washing, and training workers to identify and speak up when they see an unsanitary
condition (ill worker, product contaminated with animal faeces, frass, soil, etc.). Avoid very high pressure when
power washing to minimise aerosols created by high fluid velocity. Chemical sanitation can follow cleaning,
and sanitisers are available in several chemical classes (quaternary ammonias, alcohols, chlorine dioxide,
hypochlorite, peracetic acid). Foam formulations increase contact time, which is particularly valuable under dry
conditions. Sanitisers should never contact the fruit, and a potable water rinse after their application, but
before the tote is used, is recommended and may be required.
Monitoring sanitation
Sterile swabs or sponges are used to collect surface samples to monitor sanitation. The swabs are typically
analysed by conventional quantitative microbiological analysis (commonly total aerobic plate counts for
bacteria and on other media for total yeasts and moulds). Units for populations are expressed as colony
forming units (CFU). CFU can be very large to near zero, and are usually expressed as a log10 (e.g.
1,000,000/cm2 = 106/cm2). Analysis takes several days, while a second method, that estimates the total viable
microbiological population by the ATP (adenosine triphosphate) content on the surface sampled, takes only a
few minutes using a handheld ATP photometer or luminometer. This result indicates a non-specific
quantitative value for the density of all microbes within the sample. More specific testing for the presence of
potential human pathogens (total coliforms, enterobacteriaceae, Salmonella, etc.) must be done with care,
since positives can trigger recalls.
A 'zone' approach is recommended for sanitation monitoring, with the zones 1 to 4 defined as follows. You can
imagine there is 'Zone 0' (the product itself), but this is not part of most monitoring programs because a
positive find may trigger a recall.
Zone 1. Product contact surfaces. Belts, brushes, tables, knives, rollers, graders, includes air over
product
Zone 2. Non-product contact but nearby. Near surfaces: floors, tables, chairs, switches, handles
Zone 3. Areas within finished product storage. Phones, air handling units, drains, fork lift wheels
Zone 4. Distant areas but on-site. Cafeteria, bathrooms, lockers, ceilings, walls
Traceability and lot codes
Lots of the product should be established so they can be traced back to specific locations and dates
(Chapman and Danyluk, 2013). The nature of the sanitation actions and when they occurred should be
recorded for every lot (FDA 2013).
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Food safety
Product recalls
Confirmed finds on foods can follow from consumer complaints, supplier to customer communications, internal
food safety data, or sampling by a regulatory agency. Confirmed finds can trigger recalls. Recalls are actions
taken by a firm to remove a product from the market. Recalls may be conducted on a firm's own initiative, by
FDA request, or by FDA order under statutory authority. Elements of a recall can include public health press
releases, product seizure, facility shut down, facility de-registration, court-ordered legal actions, and even
criminal prosecution. Adverse publicity from these harm company reputation and brand recognition.

Class I recall: a situation in which there is a reasonable probability that the use of or exposure to a
contaminated product will cause serious adverse health consequences or death.

Class II recall: a situation in which use of or exposure to a contaminated product may cause
temporary or medically reversible adverse health consequences or where the probability of serious
adverse health consequences is remote.

Class III recall: a situation in which use of or exposure to a contaminated product is not likely to
cause adverse health consequences.

Market withdrawal: occurs when a product has a minor violation that would not be subject to FDA
legal action. The firm removes the product from the market or corrects the violation. For example, a
product removed from the market due to tampering, without evidence of manufacturing or distribution
problems, would be a market withdrawal.
Liability and recall insurance
Insurance is available from many companies (AIG, Crum & Foster, Lloyds, Liberty Mutual) to cover losses
caused by food safety incidents. Recall insurance provides protection for two types of losses associated with a
recall. The first is a class of general liability insurance that pays for injury, illness, or damage caused by your
products or activities. Coverage limits are typically one to two million dollars, and a variety of exclusions apply.
The second class of insurance pays for product recall expenses, such as the cost to retrieve and destroy the
product, lost income, public relations, claims, and tracking costs. A major limitation of insurance is that it must
be your product that caused the illness or damage. If the problem originated with another firm, but your firm
suffers lost sales as a consequence of their recall, you are excluded from compensation from your losses.
Additional reading and references
Chapman and Danyluk, MD. 2013. Establishing Lot Size through Sanitation Clean Breaks in Produce Packing
Facilities. University of Florida, Institute of Food and Agricultural Sciences publication FSHN13-10.
Retrieved from www.calcitrusquality.org/wp-content/uploads/Chapman-and-Danyluk-2013.pdf.
Food and Drug Administration. 2011. Full text of the Food Safety Modernization Act. Retrieved from
www.gpo.gov/fdsys/pkg/PLAW-111publ353/pdf/PLAW-111publ353.pdf.
Food and Drug Administration. 2012. The Bad Bug Book, Foodborne Pathogenic Microorganisms and Natural
Toxins Handbook 2nd ed. Retrieved from
www.fda.gov/food/foodborneillnesscontaminants/causesofillnessbadbugbook/ucm2006773.htm.
Food and Drug Administration. 2013. Current Good Manufacturing Practice and Hazard Analysis and RiskBased Preventive Controls for Human Food. 78 Federal Register 11 (16 January 2013). Retrieved from
www.gpo. gov/fdsys/pkg/FR-2013-01-16/html/2013-00125.htm.
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