This document discusses food safety and spoilage of fermented foods. It begins by defining food safety and the properties of fermented foods, noting they are generally safer than unfermented foods due to inhibition of pathogenic bacteria and toxins. However, some hazards like E. coli and viruses may survive fermentation. It emphasizes using good practices like hygiene and a Hazard Analysis Critical Control Point (HACCP) system to ensure safety. The document then discusses causes of spoilage in fermented products like beer, wine, vegetables and cheeses by various microorganisms. It concludes by outlining advances in fermentation including engineering microorganisms and metabolic pathways.

1. Safety and Spoilage of Fermented
Foods

2. FOOD SAFETY
The assurance that food will not cause harm to the consumer
when it is prepared and/or eaten according to its intended
use.
• Should not be confused with FOOD HYGIENE, which is
defined as all conditions and measures necessary to ensure
the safety and suitability of food at all stages of the food
chain.
• The No. 1 concern in the food industry
• Has been a source of concern to humankind since the dawn
of history

3. Properties of Fermented Foods
• Enhanced preservation
• Enhanced nutritional value
• Enhanced functionality
• Enhanced organoleptic properties
• Unique
• Increased economic value

4. Safety of Fermented Foods
Fermented foods are safer than their
unfermented counterpart owing to the following:
• Inhibition of the growth of most pathogenic
bacteria
• Removal of natural toxic components
• Inhibition of the formation of bacterial toxins

5. Safety of Fermented Foods
The improved food safety arising from fermentation
is largely due to lactic acid bacteria, a group of
organisms that predominate in most fermented
foods. Their growth and metabolism inhibit the
growth of normal spoilage flora of the food material
and of any bacterial pathogens that it may contain.

6. HOWEVER, a number of food-borne hazards are not controlled by
lactic acid fermentation and so present a serious threat to health if
they persist in food. Examples are the following:
• Enterohemorrhagic E. coli has shown pattern of acid resistance and
may survive certain fermentation processes. Yoghurt and fermented
meat have been recognized as potential vehicles of infection by this
microorganism.
• Food and water-borne viruses, a frequent cause of gastroenteritis,
may survive high levels of acidity.
• Most toxins produced by some algae, bacteria and molds are also
unaffected by fermentation.
THUS, it is crucial NOT TO RELY ONLY on fermentation to eliminate
or reduce hazards to safe levels.

7. For this reason, fermentation are frequently
combined with other processes such as
soaking, washing, cooking and pasteurization
to ensure adequate safety.

8. In addition, it is important to observe good food
safety practices to ensure fermented food safety.
These include the following:
• Ensuring that the starting materials used did/do not
come into contact with manure or compost
• Using good fresh food as starting materials
• Using only starting products from healthy animals.
• Observing appropriate levels of hygiene and
sanitation to avoid contamination during handling.
• Observing proper fermentation procedures.

9. In essence, this means examining the fermentation
process carefully and developing a plan where hazards
associated with the different production steps are
considered and controlled. In this regard, the Hazard
Analysis and Critical Control Point (HACCP) is the
standard method of food safety assurance.

10. HACCP
A system that identifies, evaluates and controls hazards
which are significant for food safety.
• It is a scientific, rational and systematic approach to
identifying, assessing, and controlling hazards during
production, processing, manufacturing, preparation and use
of food to ensure that food is safe when consumed.
• Conceived in the 1960s by the Pillsbury Company, NASA
and the U.S. Army Laboratories at Natick to ensure the
safety of foods for astronauts.
• In the 50 years since its conception, it has grown to become
the universally recognized and accepted method of food
safety assurance.

11. Principles of HACCP
1. Conduct a hazard analysis
2. Identify critical control points
3. Establish critical limits for each critical control point
4. Establish critical control point monitoring
requirements
5. Establish corrective actions
6. Establish procedures for ensuring the HACCP
system is working as intended
7. Establish record keeping procedures

12. Spoilage of Fermented Foods
and Beverages
Despite the low pH or ethanol content of
fermented food and beverage products, which
prohibit the growth of pathogens, spoilage
CAN still OCCUR.

13. MAJOR CAUSES OF FOOD DETERIORATION
• Growth and activities of microorganisms (bacteria, yeasts and
molds]
• Activities of food enzymes and other chemical reactions within the
food itself
• Infestation by insects (parasites and rodents)
• Inappropriate temperature for a given food
• Either the gain or loss of moisture
• Reaction with oxygen
• Exposure to light
• Physical stress or abuse
• Time

14. Beer and wine (pH 4-5) can be spoiled by yeasts and
bacteria. The bacteria involved are primarily lactic acid bacteria like
lactobacilli and Pediococcus spp., and (under aerobic conditions) acetic
acid bacteria like Acetobacter and Gluconobacter species. Acetic acid
bacteria convert ethanol to acetic acid in the presence of oxygen.
However, the anaerobic bacterium Megasphaera cerevisiae can also
spoil beer by producing isovaleric acid and H2S.
bacteria
Packaged beer undergo spoilage owing to the growth of the
yeast Saccharomyces diastaticus, which grows on dextrins that
brewer’s yeast cannot utilize.

15. Candida valida is the most important spoilage yeast in wine. In
either case, spoilage by yeasts results in the development of
turbidity, off flavors and odors.
Wines can also be spoiled by lactic acid bacteria, which
convert malic acid to lactic acid (malo-lactic fermentation). This
reduces the acidity of the wine and adversely affect wine
flavor. In some areas, wine grapes have too much malic acid so
its fermentation is deliberately used to reduce the acidity of
grape juice that will be used for wine.

16. Fermented vegetables such as sauerkraut and pickles, as well
as other acid foods like salad dressings and mayonnaise, can
be spoilt by yeasts, molds and lactic acid bacteria. Spoilage in
fermented vegetables is often manifested by off odors or
changes in the color (chromogenic colony growth) or texture
(softening) of the product. In mayonnaise or salad dressing, the
first signs of spoilage are usually off odors and emulsion
separation.

17. Cottage cheese can be spoiled by yeasts, molds and bacteria.
The most common bacterial spoilage is “slimy curd” caused
by Alcaligenes spp. (gram-negative aerobic rod bound in soil,
water, and intestinal tract of vertebrates). Like Campylobacter,
these species do not oxidize carbohydrates, but instead use
amino acids and TCA intermediates.
Penicillum, Mucor and other fungi also grow well on cottage
cheese and impart stale or yeasty flavors.

18. Ripened Cheeses, despite their low aw, low pH, and high
salt concentration, which inhibit most spoilage
microorganisms, are spoiled by surface mold growth.
Spores of C. butyricum, C. sporogenes and others can
germinate in cheeses (e.g., Swiss) with intrinsic properties
that are less inhibitory (e.g., lower salt concentration, higher
pH).
These organisms may metabolize citrate, lactose, pyruvate
or lactic acid and produce butyrate or acetate plus CO2 or
H2 gas which “blows” the cheese.

19. Advances in Food and Beverage Fermentation
1. Engineering of microorganisms for improved fermentation
• Development through genetic techniques of robust proprietary
microorganisms that can better ferment substrates to produce the
desired products.
• Engineering of innovative microbial strains that can help produce
biomolecules in bulk using improved technologies These developments
are indicative of the huge potential of fermentation as a low-cost and
flexible method of producing a range of end products.
• Recombinant DNA technology can be used to genetically improve
bacterial strains for use in industrial processes. Specific genes can be
partially or totally eliminated from a strain or replaced with different
alleles from other strains of the same genus. Likewise, new properties
can be introduced into a strain by gene transfer.

20. Advances in Food and Beverage Fermentation
2. Metabolic pathway engineering of various enzymes
Lactic acid production is dependent on lactate dehydrogenase
(LDH) activities present in lactic acid bacateria. The lactic acid
stereoisomerism is, in general, controlled by the enzymatic activity
of LDH-L or LDH-D, although, in some cases, lactate racemases
have been detected. Hence, lactic acid bacteria that contain only
one of these LDH enzymes may produce a pure enantiomer.
Lactobacillus helveticus has been the first lactic acid bacterium to
be used and combined with LDH-D inactivation, a derivative
developed that was able to produce pure L-lactic acid. By using a
similar approach, pure enantiomers of lactic acid have also been
obtained by the inactivation of specific LDH in other lactic acid
bacteria.

21. Advances in Food and Beverage Fermentation
3. Improvement of the rheological properties of fermentation
broths.
4. Development of more efficient process-driven technologies
Examples: solid-state fermentation, consolidated bioprocessing,
ultrasonication, syngas fermentation, and dark fermentation
5. New bioreactor designs
Examples: High-mass transfer chemical reactors for methanotroph
fermentation and versatile tray-type solid-state fermentation
bioreactors