Food Protection Trends - July/August 2020 - 252

turers are capitalizing on a resurgence of interest in food
fermentation. A 2018 survey of restaurant menus and sales
data from nearly 9,000 restaurants found a 149% increase
in fermented foods from the previous year (14), with chefs
and young consumers demanding fermented food and beverage options beyond traditional pickles, cheese, beer and
wine (47). Food manufacturers are addressing the increased
consumer demand for fermented foods by experimenting
with flavor and ingredient innovations. However, emerging
interest in fermented vegetable production presents the
industry and food safety regulators with the challenge of
ensuring safe finished products through the application of
process controls.
Under federal regulations implementing the Food Safety
Modernization Act (FSMA), a business that manufactures
fermented foods may be required to conduct a hazard
analysis that identifies reasonably foreseeable hazards and
determines whether identified hazards require preventive
controls. If the need for a preventive control is identified,
written documentation of monitoring and verification
procedures, corrective actions, and a recall plan are required (55). Similarly, a retail food establishment seeking
a variance to engage in fermentation under the FDA Food
Code is generally required to submit a HACCP plan to the
pertinent regulatory agency for review (54). For either food
manufacturers or retail food establishments, the process of
systematically identifying relevant hazards and developing
targeted interventions would apply. Developing food safety
programs can be a challenge for small-scale producers with
little access to training and resources, especially as manufacture of fermented vegetable products involves microbiologically complex systems that may not be effectively or appropriately managed by standard time-temperature controls.
Food fermentation has a long tradition of improving
not only the shelf life and acceptability but also the safety
of foods. For most vegetable fermentations, the fermentation environment suppresses the growth of pathogenic
or spoilage bacteria because of decreasing pH, low-oxygen
conditions, and robust growth of lactic acid bacteria, with
the associated production of organic acids and other inhibitory compounds (5, 13). There have been, however, several
instances of foodborne illness outbreaks linked to "lightly"
fermented or under-acidified vegetable products, particularly kimchi (9, 21, 27, 45, 49). The goal of this manuscript
is to describe the microbiology behind traditional vegetable
fermentation processes and to outline best practices for
safe, small-scale manufacture of fermented vegetables, such
as cabbage, peppers, and cucumbers.
Vegetable fermentation: The science
Food fermentation technology likely dates to the origin
of pottery, a necessary antecedent, at the end of the Pleistocene era around 11,000 years ago. It was not until the early
1900s, however, that scientific research on the microbiology

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Food Protection Trends July/August

and chemistry of vegetable fermentations was first reported
(11, 29, 38). Since these early reports, extensive research
has been conducted on vegetable fermentation microbiology and biochemistry, and comprehensive reviews are available (5, 12, 15, 36, 45). Traditionally fermented vegetables
include cabbage, cucumbers, peppers and olives. Important
in the success and safety of vegetable fermentations are
the establishment of fermentative organisms, principally
lactic acid-producing bacteria; elevated NaCl concentration; proper ambient temperature, and a reduced dissolved
oxygen concentration. In most vegetable fermentations,
epiphytic aerobic microbiota are replaced by a succession
of facultatively anaerobic, acid-tolerant lactic acid bacteria
(LAB) (Fig. 1). Temperature, NaCl concentration, organic
acid concentration, and pH can influence the growth and
survival of LAB microbiota. LAB have a fermentative (anaerobic) metabolism and predominate in NaCl brines as pH
drops and organic acids accumulate (5, 8).

FIGURE 1. The effect of temperature on the relative abundance of
microbiota for nabak (sliced) kimchi. Relative abundance is shown
for nabak fermentations at (A) 4°C, (B) 10°C, and (C) 20°C. The color
codes for each population are indicated in the legend (28). X-axis labels
refer to specific samples analyzed, e.g., C0407 is stored at 4°C with brine
sampled on day 7, C0421 is stored at 4°C with brine sampled on day 21.
For a full description of experimental design see reference (28).

Cabbage-based products such as sauerkraut and kimchi
are optimally fermented at 18°C and an NaCI concentration
of around 2% (45, 46). The initial pH of most vegetable fer-

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