206 Modern Food Microbiology
DEHYDRATED FOODS
In a detailed study of the microbiology of dehydrated soups, Fanelli et al.
10,11 showed that approximately 17 different kinds of dried soups from nine different processors had total counts of less than
log 10 /g 5.00. These soups included chicken noodle, chicken rice, beef noodle, vegetable, mushroom,
pea, onion, tomato, and others. Some of these products had total counts as high as log 10 /g 7.30, and
some had counts as low as around log 10 2.00. These investigators further found that reconstituted
dehydrated onion soup showed a mean total count of log 10 /ml 5.11, with log 10 3.00 coliforms, log 10
4.00 aerobic spore formers, and log 10 /ml 1.08 of yeast and molds. Upon cooking, the total counts
were reduced to a mean of log 10 2.15, whereas coliforms were reduced to <0.26, spore formers to
log 10 1.64, and yeasts and molds to log 10 /ml <1.00. In a study of dehydrated sauce and gravy mixes,
soup mixes, spaghetti sauce mixes, and cheese sauce mixes, C. perfringens was isolated from 10 of
55 samples.
42 The facultative anaerobe counts ranged from log 10 /g 3.00 to >6.00. In a study of 185
samples of food-grade dry gelatin, no samples exceeded an APC of log 10 /g 3.70.
33 Of 129 dehydrated
space food samples examined, 93% contained total counts log 10 /g <4.00.
47
Powdered eggs and milk often contain high numbers of microorganisms—on the order of log 10 /g
6–8. One reason for the generally high numbers in dried products is that the organisms have been concentrated on a per gram basis along with product concentration. The same is generally true for fruit juice
concentrates, which tend to have higher numbers of microorganisms than the fresh, nonconcentrated
products.
ENTERAL NUTRIENT SOLUTIONS (MEDICAL FOODS)
Enteral nutrient solutions (ENS), also known as medical foods, are liquid foods administered by
tube. They are available as powdered products requiring reconstitution or as liquids. They are generally
administered to certain patients in hospitals or other patient care facilities, but may also be administered
in the home. Administration is by continuous drip from enteral feeding bags, and the process may go on
for 8 hours or longer, with the ENS at room temperature. Enteral foods are made by several commercial
companies as complete diets that only require reconstituting with water before use, or as incomplete
meals that require supplementation with milk, eggs, or the like prior to use. ENS-use preparations are
nutritionally complete, with varying concentrations of proteins, peptides, carbohydrates, and so forth,
depending on patient need.
The microbiology of ENS has been addressed by some hospital researchers, who have found the
products to contain varying numbers and types of bacteria and to be the source of patient infections.
Numbers as high as 10
8 /ml have been found in some ENS at time of infusion.
14 In a study of one reconstituted commercial ENS, the initial count of 9 × 10
3 /ml increased to 7 × 10
4 /ml after 8 hours at room
temperature.
20 Numbers as high as 1.2 × 10
5 /ml were found in another sample of the same preparation.
The most frequently isolated organism was Staphylococcus epidermidis, with Corynebacterium, Citrobacter, and Acinetobacter spp. among the other isolates. From a British study, enteral feeds yielded
10
4
− 10
6 organisms/ml, with coliforms and Pseudomonas aeruginosa as the predominant types.
15
The capacity of five different commercial ENS to support the growth of Enterobacter cloacae
under use conditions has been demonstrated,
9 and the addition of 0.2% potassium sorbate was shown
to reduce numbers of this organism by three log cycles over controls. Patients are known to have
contracted E. cloacae and Salmonella Enteritidis infections from ENS.
4,14 Procedures that should be
employed in the preparation/handling of ENS to minimize microbial problems have been noted.
17 For
a review of the history and other nonmicrobial aspects of ENS or medical foods (see reference 52).
DEHYDRATED FOODS
In a detailed study of the microbiology of dehydrated soups, Fanelli et al.
10,11 showed that approximately 17 different kinds of dried soups from nine different processors had total counts of less than
log 10 /g 5.00. These soups included chicken noodle, chicken rice, beef noodle, vegetable, mushroom,
pea, onion, tomato, and others. Some of these products had total counts as high as log 10 /g 7.30, and
some had counts as low as around log 10 2.00. These investigators further found that reconstituted
dehydrated onion soup showed a mean total count of log 10 /ml 5.11, with log 10 3.00 coliforms, log 10
4.00 aerobic spore formers, and log 10 /ml 1.08 of yeast and molds. Upon cooking, the total counts
were reduced to a mean of log 10 2.15, whereas coliforms were reduced to <0.26, spore formers to
log 10 1.64, and yeasts and molds to log 10 /ml <1.00. In a study of dehydrated sauce and gravy mixes,
soup mixes, spaghetti sauce mixes, and cheese sauce mixes, C. perfringens was isolated from 10 of
55 samples.
42 The facultative anaerobe counts ranged from log 10 /g 3.00 to >6.00. In a study of 185
samples of food-grade dry gelatin, no samples exceeded an APC of log 10 /g 3.70.
33 Of 129 dehydrated
space food samples examined, 93% contained total counts log 10 /g <4.00.
47
Powdered eggs and milk often contain high numbers of microorganisms—on the order of log 10 /g
6–8. One reason for the generally high numbers in dried products is that the organisms have been concentrated on a per gram basis along with product concentration. The same is generally true for fruit juice
concentrates, which tend to have higher numbers of microorganisms than the fresh, nonconcentrated
products.
ENTERAL NUTRIENT SOLUTIONS (MEDICAL FOODS)
Enteral nutrient solutions (ENS), also known as medical foods, are liquid foods administered by
tube. They are available as powdered products requiring reconstitution or as liquids. They are generally
administered to certain patients in hospitals or other patient care facilities, but may also be administered
in the home. Administration is by continuous drip from enteral feeding bags, and the process may go on
for 8 hours or longer, with the ENS at room temperature. Enteral foods are made by several commercial
companies as complete diets that only require reconstituting with water before use, or as incomplete
meals that require supplementation with milk, eggs, or the like prior to use. ENS-use preparations are
nutritionally complete, with varying concentrations of proteins, peptides, carbohydrates, and so forth,
depending on patient need.
The microbiology of ENS has been addressed by some hospital researchers, who have found the
products to contain varying numbers and types of bacteria and to be the source of patient infections.
Numbers as high as 10
8 /ml have been found in some ENS at time of infusion.
14 In a study of one reconstituted commercial ENS, the initial count of 9 × 10
3 /ml increased to 7 × 10
4 /ml after 8 hours at room
temperature.
20 Numbers as high as 1.2 × 10
5 /ml were found in another sample of the same preparation.
The most frequently isolated organism was Staphylococcus epidermidis, with Corynebacterium, Citrobacter, and Acinetobacter spp. among the other isolates. From a British study, enteral feeds yielded
10
4
− 10
6 organisms/ml, with coliforms and Pseudomonas aeruginosa as the predominant types.
15
The capacity of five different commercial ENS to support the growth of Enterobacter cloacae
under use conditions has been demonstrated,
9 and the addition of 0.2% potassium sorbate was shown
to reduce numbers of this organism by three log cycles over controls. Patients are known to have
contracted E. cloacae and Salmonella Enteritidis infections from ENS.
4,14 Procedures that should be
employed in the preparation/handling of ENS to minimize microbial problems have been noted.
17 For
a review of the history and other nonmicrobial aspects of ENS or medical foods (see reference 52).