Factors affecting the microbiological stability of ketchup

1. KETCHUP
Chandrima Shrivastava
13FET1001

2. Composition
“The concentrated product prepared from the liquid extracted from
sound, ripe, red or reddish tomatoes, and seasoned with characterizing
ingredients such as pepper, onions, vinegar and sugar in quantities that
materially alter the flavour, aroma and taste of the tomato component”
INGREDIENTS
Water
Sugar
Tomato Solids (Tomato Paste (22.5%))
Salt
Vinegar/Acetic Acid (0.8%)
Starch
Sodium benzoate
Onion Powder, Garlic Powder
Spices and Condiments

3. Intrinsic Factors
 pH
 Water activity
 Redox Potential
 Nutrient content
 Antimicrobial Barriers and Constituents

4. pH
 Ketchup contains 20% natural tomato soluble solids by weight
 pH of tomatoes is in the range 3.9 - 4.9
 Tomatoes inherently contain citric acid as the predominant acid
and malic acid in low concentration, traces of acetic and lactic acid
may also be present
 Consequently, pH of ketchup is normally between 3.89 and 3.92
 Microorganisms predominantly acidophiles
 Lower pH prevents bacterial growth, spoilage mainly caused by
yeasts, molds and lactic acid bactria
pH ranges of different microbial groups

5. Water activity (aw)
 Tomato is a High Water Content Vegetables: 94%-95% weight of tomato is
water
 High sugar, salt and dry matter content in ketchup results in a reduction in
water activity levels to 0.93
 The water activity requirement decreases as: Bacteria > Yeast > Mold
 If a food has aW <= 0.85, it is generally considered as non-hazardous
Minimum water activity values of spoilage
microorganisms
Susceptibility to spoilage based on
aw

6. Redox Potential
 Ketchup has an Eh of roughly +400 mV
 Redox potential represents the sum of all compounds present that
influence onidation-reduction reactions
 It also affects the solubility of nutrients, especially mineral ions
 Antioxidants are also known as redox-active compounds
 Tomato contains lycopene (processed foods better sources of
bioavailable lycopene than fresh tomatoes )
 Plant pigments are sensitive to redox potential, and changes affect
the colour
 Strictly aerobic microorganisms can grow only in positive Eh values
 Redox potential also influenced by amount of undissociated acetic
acid

7. Nutrient Content
 Sugar or high-fructose corn syrup form a major part (20% - 30%) of
the total solids
 Starch may be added to give the required consistency
 Fruits tend to be low in B vitamins than meats, which explains their
spoilage by molds rather than bacteria (molds are able to synthesize
most of their requirements)
NUTRITIONAL INFORMATION (per 100 g)
Water (65 g)
Protein (traces)
Carbohydrates (33 g) - added Sugar (27
g)
Fat (0.5 g)
Minerals - Sodium (1070 mg)
Vitamin C (15 mg)
Lycopene (17 mg)

8. Antimicrobial Barriers and
Constituents
 Tomato inherently contains citric acid as the predominant
acid and malic acid in low concentrations, traces of acetic
and lactic acids may also be present
 Ketchup contains spices like cinnamon (cinnamic
aldehyde), cloves (eugenol) and cayenne, garlic (allicin) -
naturally occurring substances possessing antimicrobial
activity
 Ketchup preserved with benzoic acid or sorbic acid
 Amount of vinegar added typically results in 0.8% to 1% of
acetic acid in the product

9. Extrinsic Factors
 Temperature of storage
 Relative humidity of the environment
 Presence and concentration of gases

10. Temperature of Storage
 Ketchup is refrigerated after opening, which extends the
shelf life
 When stored at ambient temperatures, mesophiles and
certain thermophiles like Bacillus, Clostridium may grow
Ketchup, opened Pantry Refrigerator
Shelf-life 1 month 8-12 months

11. Relative humidity of the environment
 Relative humidity and water activity are interrelated
 When ketchup is stored in environment of high humidity, water will
transfer from the gas phase to the food and thus increasing the aW ,
leading to spoilage by the viable flora
 Foods that undergo surface spoilage from molds, yeasts, and some
bacteria should be stored in conditions of low relative humidity to
increase their shelf life
 Ketchup, if not refrigerated, should be stored in closed, air tight
containers
 Variations in storage temperature should be minimal to avoid
surface condensation

12. Presence and concentration of gases
 Oxygen is one of the most important gases which come in contact with
food influence the redox potential
 Ketchup is oxygen-sensitive and should be stored in air-tight containers –
EVOH (ethylene vinyl alcohol) gas barrier properties
 The inhibitory effect of CO2 on the growth of microorganisms is applied in
modified atmosphere packaging of foods
 With regards to the effect of CO2 on microorganisms, molds and Gram-
negative bacteria are the most sensitive, while the gram-positive bacteria,
particularly the lactobacilli are tend to be more resistant
Pantry Refrigerator
Ketchup,
opened
1 month 8-12 months
Ketchup,
unopened
1 year - -

13. Implicit Factors
 Synergism
 Antagonism

14. Synergism
 When the pH of a food is 4.6 or below, spores of C. botulinum will not
germinate and grow
 When critical factors are not carefully controlled, the vegetative cells
of some microorganisms of nonhealth significance (such as some
spoilage bacteria, yeasts, and molds) can grow in an acid
environment and, in so doing, cause the pH of the food to increase
 Bacillus coagulans strain could raise the pH to over 5.0 under aerobic
conditions
 In addition, when critical factors are not properly controlled, spoilage
microorganisms (such as Bacillus licheniformis) produce heat-
resistant, acid-tolerant spores that can germinate, grow, and cause
the pH to increase
 Thermal processing may not be sufficient to destroy their spores
C.

15. Antagonism
 Secondary metabolites produced by lactic acid bacteria have antagonistic
activity include the compound reuterin and the recently discovered
antibiotic reuterocyclin, produced by strains of Lactobacillus reuteri
 Reuterin has a broad spectrum of activity and inhibits fungi, protozoa
and a wide range of bacteria including both gram-positive and gram-
negative bacteria
 Reuterocyclin, the antibiotic produced by LAB, has a spectrum of
inhibition confined to gram-positive bacteria including Lactobacillus spp.,
Bacillus subtilis, Bacillus cereus, Enterococcus faecalis, Staphylococcus
aureus and Listeria innocua
 Inhibition of Escherichia coli and Salmonella is observed under conditions
that disrupt the outer membrane, including truncated
lipopolysaccharides (LPS), low pH and high salt concentrations - mode of
action similar to nisin

16. Antagonism
 The interaction between two or more chemical substances in the
body that reduces the effect that each substance has individually
 The combination of acid and osmolytes (salts, sugars) is a common
application of ‘hurdle technology’
 Under certain conditions, osmolytes appear to protect Escherichia
coli and Salmonella enteric against inimical acetic acid challenge due
to cell envelope changes that accompany exposure to combined
acetic acid and osmotic stress
 Changes such as maintenance of outer membrane integrity and
some increase in the cardiolipin content of the cytoplasmic
membrane contribute to osmolyte protection of E. coli and S.
enterica against acetic acid inactivation

17. Antagonism
 C. pasteurianum produces carbon dioxide
 Lactobacillus fructivoras also hydrolyze sucrose products to
produce carbon dioxide
 The inhibitory effect of CO2 - molds and Gram-negative bacteria are
the most sensitive, while the gram-positive bacteria, particularly
the lactobacilli are tend to be more resistant

18. Ketchup Hurdles
 Acidity provided from tomatoes and added vinegar (pH 3.9)
 Multiple boiling steps
 Concentration and lowering aw value from added salt and sugars
 Pasteurization, hot filling and cooling of bottles
 Refrigeration after opening
 Newer processing techniques – UV treatment, irradiation

19. Spoilage Microorganisms
 The initial microflora of ketchup depends largely on the raw materials used
 Ketchup is made by mixing all ingredients, which are then cooked to 85o to
90oC, followed by hot filling into bottles - this eliminates contamination from
raw materials or the manufacturing process - free of vegetative spoilage
organisms
 pH < 4.0, hence spoilage microbes usually restricted to non-spore forming
bacteria (lactic acid bactria), or yeasts (Saccharomyces spp., Candida spp.) or
molds (Byssochlamus fulva)
 Bacillus coagulans can also cause spoilage at pH 3.8 - 4.0, but growth is
inhibited even by low concentrations of acetic acid
 Heterofermentative lactobacilli cause gas formation in ketchup
 Due to absence of liquid egg and dairy ingredients in ketchup, there is no
direct association of pathogens - herbs and spices may introduce Salmonella,
but these are killed by the cooking process or inactivated by acetic acid

20. Lactobacilli
 Ketchup is often sensitive to spoilage by lactobacilli; L. brevis, L.
mannitopeum, and L. plantarum as spoilage organisms identified in studies
of tomato ketchup
 The lactobacilli are controlled by cooking and hot filling at temperatures
above 7O0C
 In products filled at lower temperatures, lactobacilli are the predominant
spoilage organisms
 Lactobacilli can be present in spoiled products in the form of large white
spots or as small, hard, white dots, which may easily be mistaken for
undissolved ingredients or clumps of starch
 The lactobacilli can grow with or without gas formation. In the former case,
swelling of plastic containers will be seen.
 Lactobacillus brevis commonly causes fermentation of tomato ketchup.
Other lactobacilli and leuconostocs occasionally cause spoilage of ketchup.
These lactic acid bacteria produce gas as well as acid from the sugar so that
spoilage is accompanied by can distension; other end products include
acetic acid and ethyl alcohol so that with these diverse products such as
lactic acid bacteria are termed 'heterofermentative'

21. Yeasts and Molds
 Yeasts are extremely heat-sensitive and therefore rarely cause spoilage
 Zygosaccharomyces bailii and Pichia membranaefaciens, can both multiply
in the presence of 3% acetic acid, but require the presence of oxygen,
therefore spoilage only occurs at the surface
 Other species found are Zygosaccharomyces rouxii, Saccharomyces
cerevisiae and Candida magnolia
 Ketchup containing 0.8% acetic acid can be spoiled by Saccharomyces spp. -
resistant to acetic acid due to an inducible energy-requiring transport
system that removes acetic acid ions from the cells
 Yeasts may cause spoilage by gas formation or by growing as brownish
colonies, which may appear as small oil-like droplets - explosion of glass
bottles with ketchup is a hazard
 Molds, like yeasts, rarely cause spoilage, but two notable exceptions are
Byssochlamys fulva and B. nivea the ascospores of which are unusually heat-
resistant tolerating 85oC for 30 min

22. Packaging
ConAgra launches a stand up pouch
for tomato ketchup - an eye catching,
economic alternative for consumers
to PET bottle
Heinz "Dip and Squeeze”
packets far less messy
than the traditional
MIT creates superhydrophobic
coating for condiment bottles,
called LiquiGlide - it does not let
ketchup stick to the surface of
bottles - FDA approved
Extension from packing
ketchup in glass bottles to
squeezable co-extruded
multi-layer plastic bottles
with oxygen barrier
material (EVOH) for shelf
life of 12-18 months

23. AIP technologies
 The active packaging and intelligent or smart packaging systems are combined in the
platform to AIP technologies
 Active packaging describes mainly food packaging that interacts chemically or
biologically with its contents or head space to extend shelf-life
 Oxygen scavengers incorporated into the core layers of polyester in ketchup bottles or
sachets – (reduced iron–based oxygen scavenger sachet products , ascorbic acid–based
oxygen scavenger sachets)
 Antimicrobial agents incorporated into packaging materials
 A glass bottle of tomato ketchup with a self-assembly Time-Temeprature Indicator (TTI)
closure will inform the freshness status of product and remind the consumer to keep
this product in the fridge for longer shelf life - the observable colour change correlates
with the negative influence of the microbiological process