CSpoilage of Fruit Juices

(1) Flat or buttermilk flavor. The lactobacilli are important in the spoilage of fruit juices. Some strains are quite acid tolerant and can metabolize citric and malic acid. This reduces the acidity and results in a bland, rather flat flavor and a loss in astringency. A buttermilk flavor results in the fruit juice.

(2) Slimy consistency. Bacteria of the species Leuconostoc mesenteroides produces a slimy, unpleasant consistency of fruit juices.

(3) Fermentation. Yeasts contaminate and ferment fruit juice, especially apple juice. The sugars are fermented to alcohol which is converted to acetic acid, giving the fruit juice a vinegar flavor.

d. Spoilage of Meat Products. Canned meat products are subject to the same type of spoilage as other low-acid foods, if heat-resistant spores which survive the process can germinate and grow. In semipreserved or pasteurized cured products, such as canned ham, the curing salts and refrigeration are used to prevent spore germination and growth. If not adequately processed, thermoduric cells, such as Streptococcus faecium, may survive and cause souring. This organism may cause rapid discoloration after the product is removed from the can. If the spores of clostridia are able to germinate, gas may be formed along with extensive putrefaction.

e. Spoilage of Salad Dressing. The spoilage of mayonnaise and salad dressings is caused by Saccharomyces bailii and Lactobacillus fructivorans. Rather low numbers of the yeast and bacteria are present in the spoiled product.

f. Spoilage of Tomato Juice. Canned tomato juice is subject to flat sour spoilage if not properly handled either during preparation or final heat treatment. Flat sour spoilage is attributed to the presence of and growth of Bacillus coagulans, which either survives normal heat processes or recontaminates the product. Detection of spoilage is made by flavor, pH, and odor.

g. Spoilage of Assorted Products. Cereals, honey, molasses, syrup, and candy ordinarily have water activities too low to support the growth of bacteria. However, due to storage at high relative humidity or production of water by metabolism, bacteria can be responsible for the spoilage of these products.

h. Spoilage of Bottled Sauces. The gas-forming Lactobacillus lycopersici causes fermentation in tomato catsup, other tomato products, Worcestershire sauce, and similar products.

i. Spoilage of Canned Peaches and Pineapple. Canned pineapple occasionally exhibits spoilage caused by gas-formers, Leuconostoc mesenteriodes. This organism may also cause ropiness in canned peaches.

j. Spoilage of Packaged Milk. Occasionally, heat-resisting, anaerobic bacteria cause trouble in milk packs. The anaerobes produce off-flavors, thinning, curdling, and so forth, in canned milk.

k. Summary. Figure 6-1 is a summary of microbial conditions found in semiperishable subsistence.

PRODUCT

CONDITION

Canned fruit

Butyric acid, Soft rot

Canned apricots

Softening

Canned grapefruit

Gas (C02)

Fruit juice

Souring, C02 Acetification (production of acetic acid or vinegar} Moldy surface, Cloudy, Buttermilk flavor

Jelly, jam preserves

Fermentation, moldy

Canned corn, green beans, peas

Flat sour, Sulfide stinker, Putrid swell, Hard swell

Canned tomatoes

Flat sour, Butyric fermentation

Pickles

Soft, Black, Soft, mushy, slimy, Reduced acidity

Sauerkraut

Pink

Vegetable juice

Sour

Bread

Ropy, slime, Black mold, Blue mold, Pink mold, Sour, Red

Cereals, grains

Moldy, Discoloration, Pink

Honey

Fermented, yeasty

Molasses

Gas, frothy

Canned meat

Gas, souring, putrefaction, discoloration

Figure 6-1. Microbial conditions of semiperishable subsistence. 6-4. OXIDATIVE RANCIDITY

a. General. Examine the product and note any color, texture, flavor, and/or odor abnormalities. Check for the presence of oxidative rancidity.

b. Characteristics. Oxidative rancidity is caused by oxidation of unsaturated fats. Products with a high degree of unsaturated fats are most susceptible to oxidative rancidity. In freeze-dehydrated items, the rancidity will be in the lean rather than the fat component of the food item.

c. Odor and Flavor. The odor is acrid, sharp, and biting. A rancid flavor may be present and will vary depending on the stage of reaction.

d. Reference. A discussion of oxidative rancidity may be found in paragraph

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