186 Modern Food Microbiology
ciders, the initial number was reduced only to 2.9 log 10 cfu/ml after 10 days at 20
◦ C. Although the pH
of the two products was not significantly different, ethanol concentration in the fermenting products
reached 6.1% after 10 days at 20
◦ C. The investigators believed the combination of low pH and the
ethanol were important in the reduction of the pathogen. In another study of E. coli 0157:H7 survival
in four apple varieties (Golden Delicious, Red Delicious, Rome, and Winesap), the organism behaved
essentially the same in each variety.
28
Distilled Spirits
Distilled spirits are alcoholic products that result from the distillation of yeast fermentations of
grain, grain products, molasses, or fruit or fruit products. Whiskeys, gin, vodka, rum, cordials, and
liqueurs are examples of distilled spirits. Although the process for producing most products of these
types is quite similar to that for beers, the content of alcohol in the final products is considerably
higher than for beers. Rye and bourbon are examples of whiskeys. In the former, rye and rye malt, or
rye and barley malt, are used in different ratios, but at least 51% rye is required by law. Bourbon is
made from corn, barley malt, or wheat malt, and usually another grain in different proportions, but at
least 51% corn is required by law. A sour wort is maintained to keep down undesirable organisms, the
souring occurring naturally or by the addition of acid. The mash is generally soured by inoculating
with a homolactic such as L. delbrueckii subsp. delbrueckii, which is capable of lowering the pH to
around 3.8 in 6–10 hours.
58 The malt enzymes (diastases) convert the starches of the cooked grains to
dextrins and sugars, and upon completion of diastatic action and lactic acid production, the mash is
heated to destroy all microorganisms. It is then cooled to 75–80
◦ F (24–27
◦ C) and pitched (inoculated)
with a suitable strain of S. cerevisiae for the production of ethanol. Upon completion of fermentation,
the liquid is distilled to recover the alcohol and other volatiles, and these are handled and stored under
special conditions relative to the type of product being made. Scotch whisky is made primarily from
barley and is produced from barley malt dried in kilns over peat fires. Rum is produced from the
distillate of fermented sugar cane or molasses. Brandy is a product prepared by distilling grape or
other fruit wines.
Palm wine or Nigerian palm wine is an alcoholic beverage consumed throughout the tropics and
is produced by a natural fermentation of palm sap. The sap is sweet and dirty brown in color, and it
contains 10–12% sugar, mainly sucrose. The fermentation process results in the sap becoming milkywhite in appearance due to the presence of large numbers of fermenting bacteria and yeasts. This
product is unique in that the microorganisms are alive when the wine is consumed. The fermentation
has been reviewed and studied by Faparusi and Bassir
26 and Okafor
49 who found the following genera of
bacteria to be the most predominant in finished products: Micrococcus, Leuconostoc, “Streptococcus,”
Lactobacillus, and Acetobacter. The predominant yeasts found were Saccharomyces and Candida spp.,
with the former being the more common.
48 The fermentation occurs over a 36- to 48-hour period,
during which the pH of sap falls from 7.0 or 7.2 to <4.5. Fermentation products consist of organic acids
in addition to ethanol. During the early phases of fermentation, Serratia and Enterobacter spp. increase
in numbers, followed by lactobacilli and leuconostocs. After a 48-hour fermentation, Acetobacter spp.
begin to appear.
26,50
Sake is an alcoholic beverage commonly produced in Japan. The substrate is the starch from steamed
rice, and its hydrolysis to sugars is carried out by A. oryzae to yield the koji. Fermentation is carried
out by Saccharomyces sake over periods of 30–40 days, resulting in a product containing 12–15%
alcohol and around 0.3% lactic acid.
58 The latter is produced by hetero- and homolactic lactobacilli.
Other fermented products of this type are further summarized in Table 8–1.
ciders, the initial number was reduced only to 2.9 log 10 cfu/ml after 10 days at 20
◦ C. Although the pH
of the two products was not significantly different, ethanol concentration in the fermenting products
reached 6.1% after 10 days at 20
◦ C. The investigators believed the combination of low pH and the
ethanol were important in the reduction of the pathogen. In another study of E. coli 0157:H7 survival
in four apple varieties (Golden Delicious, Red Delicious, Rome, and Winesap), the organism behaved
essentially the same in each variety.
28
Distilled Spirits
Distilled spirits are alcoholic products that result from the distillation of yeast fermentations of
grain, grain products, molasses, or fruit or fruit products. Whiskeys, gin, vodka, rum, cordials, and
liqueurs are examples of distilled spirits. Although the process for producing most products of these
types is quite similar to that for beers, the content of alcohol in the final products is considerably
higher than for beers. Rye and bourbon are examples of whiskeys. In the former, rye and rye malt, or
rye and barley malt, are used in different ratios, but at least 51% rye is required by law. Bourbon is
made from corn, barley malt, or wheat malt, and usually another grain in different proportions, but at
least 51% corn is required by law. A sour wort is maintained to keep down undesirable organisms, the
souring occurring naturally or by the addition of acid. The mash is generally soured by inoculating
with a homolactic such as L. delbrueckii subsp. delbrueckii, which is capable of lowering the pH to
around 3.8 in 6–10 hours.
58 The malt enzymes (diastases) convert the starches of the cooked grains to
dextrins and sugars, and upon completion of diastatic action and lactic acid production, the mash is
heated to destroy all microorganisms. It is then cooled to 75–80
◦ F (24–27
◦ C) and pitched (inoculated)
with a suitable strain of S. cerevisiae for the production of ethanol. Upon completion of fermentation,
the liquid is distilled to recover the alcohol and other volatiles, and these are handled and stored under
special conditions relative to the type of product being made. Scotch whisky is made primarily from
barley and is produced from barley malt dried in kilns over peat fires. Rum is produced from the
distillate of fermented sugar cane or molasses. Brandy is a product prepared by distilling grape or
other fruit wines.
Palm wine or Nigerian palm wine is an alcoholic beverage consumed throughout the tropics and
is produced by a natural fermentation of palm sap. The sap is sweet and dirty brown in color, and it
contains 10–12% sugar, mainly sucrose. The fermentation process results in the sap becoming milkywhite in appearance due to the presence of large numbers of fermenting bacteria and yeasts. This
product is unique in that the microorganisms are alive when the wine is consumed. The fermentation
has been reviewed and studied by Faparusi and Bassir
26 and Okafor
49 who found the following genera of
bacteria to be the most predominant in finished products: Micrococcus, Leuconostoc, “Streptococcus,”
Lactobacillus, and Acetobacter. The predominant yeasts found were Saccharomyces and Candida spp.,
with the former being the more common.
48 The fermentation occurs over a 36- to 48-hour period,
during which the pH of sap falls from 7.0 or 7.2 to <4.5. Fermentation products consist of organic acids
in addition to ethanol. During the early phases of fermentation, Serratia and Enterobacter spp. increase
in numbers, followed by lactobacilli and leuconostocs. After a 48-hour fermentation, Acetobacter spp.
begin to appear.
26,50
Sake is an alcoholic beverage commonly produced in Japan. The substrate is the starch from steamed
rice, and its hydrolysis to sugars is carried out by A. oryzae to yield the koji. Fermentation is carried
out by Saccharomyces sake over periods of 30–40 days, resulting in a product containing 12–15%
alcohol and around 0.3% lactic acid.
58 The latter is produced by hetero- and homolactic lactobacilli.
Other fermented products of this type are further summarized in Table 8–1.