254 Produce Degradation: Reaction Pathways and their Prevention
vinegar (Battcock and Azam-Ali, 1998). The most commonly known fermented
produce is sauerkraut. Sauerkraut, which is prepared from cabbage, was consumed
from the Roman times and was highly prized for its delicious taste as well as
medicinal properties. Apart from cabbage, other fruits and vegetables used in acid
fermentation include cucumbers, beets, green tomatoes, peppers, lettuce, eggplant,
onion, squash, carrots, and turnips. For example, pickled green tomatoes, peppers,
and lettuce are widely eaten in Russia and Poland, while in Asia, pickled preparations
of cabbage, turnips, eggplant, cucumber, onion, squash, and carrot are popular. The
popular Korean kimchi is a fermented condiment of cabbage with other vegetables
and seasonings. In America, popular acid-fermented products include corn and
cucumber relishes, fruit chutneys, and watermelon rind (Battcock and Azam-Ali,
1998; Hartley et al., 2001).
8.10.4.3 Alkaline Fermentation
Alkaline fermentation is carried out by the Bacillus species. Many bacterial species
belong to this family, such as Bacillus subtilis, Bacillus lichifornis, and Bacillus
pumilius, but B. subtilis is the dominant species (Battcock and Azam-Ali, 1998;
Hartley et al., 2001). Alkaline fermentation bacteria act by hydrolyzing protein in
food to form amino acids and peptides and releasing ammonia in the process, which
increases the alkalinity of the food. Like acid fermentation, alkaline fermentation
alters the pH of food, making it unsuitable for growth of other microorganisms that
may decompose or spoil the food. Alkaline fermentations are more common with
protein-rich foods such as soybeans and other legumes, although there are a few
examples utilizing fruits and vegetables. For example, watermelon seeds (Ogiri in
Nigeria) and green vegetables (Semayi in Indonesia and Kawal in Sudan) are used
as substrates for alkaline fermentation (Battcock and Azam-Ali, 1998). Alkaline-
fermented products are important in providing protein-rich, low-cost condiments
from green vegetables, seeds, and beans that contribute to the diet of millions of
people, especially in developing countries.
Preservation of fruits and vegetables by the process of fermentation has numer-
ous advantages beyond those of simple preservation. Fermented products retain most
of their ascorbic acid contents; however, the retention depends on the fermentation
temperature and the fermenting time. When properly packaged and stored in cool,
dark place, most fermented products would retain their good texture and flavor.
When fermented foods are exposed to light and high temperature there is discolor-
ation, degradation of vitamin C, and off-flavor development (Salunkhe, 1974).
8.10.5 PROBIOTICS
The role of probiotics in foods, and indeed in some fermented produce products,
has also been recognized as beneficial to health, especially in the past decade, and
will be discussed in this section.
Probiotics are beneficial bacteria, such as Lactobacillus acidophilus and Bifido-
bacterium bifidum (Teitelbaum and Walker, 2002). Beneficial bacteria generally
include three lactic acid genera, namely, Bifidobacterium (bifidum, breve, infantis,