Microbial Spoilage

a. Relatively Rapid Deterioration. From the moment fish are taken from the water, a series of deteriorative changes start to occur which eventually will render the fish unmarketable. Since these changes occur relatively rapidly, fish are probably the most perishable of all flesh foods. Microbiological action produces the most extensive of the deteriorative changes.

b. Product Examination by the Inspector. Examine the product and note abnormal color(s), odor(s), and/or texture(s) typical of microbial deterioration. Microbial spoilage may be caused by bacteria, mold, and/or yeasts. The particular color, odor, or texture change(s) involved will depend upon the type or species of microorganism involved.

c. Caution to the Inspector and Appropriate Action. If microbial spoilage is suspected, THE INSPECTOR SHOULD NOT TASTE THE PRODUCT. He should contact the veterinary officer for further examination of the product.

d. Color Changes. The following color changes may indicate microbial spoilage: red, pink, chocolate brown, yellowish green, black, brown, and so forth e. Odor Changes. The following odor changes have been associated with microbial deterioration: muddy, musty, sour, putrid, soapy, milky, fecal, brine-like, sweet, yeasty, ammonia, hydrogen sulfide, fruity, dishraggy, wet hair, wet dog, and so forth.

f. Changes in Texture. The following textural changes may be associated with microbial deterioration: slimy, foamy, bubbly, soft, honeycombed, turbid, and jellylike.

g. Flavor Changes. Even though you, the 91R20, will NOT taste the product, you should be aware that the following flavor changes have been associated with microbial deterioration: muddy, musty, feedy (like animal feed).

h. Common Spoilage Organisms. The most common type of spoilage organisms in fish are gram-negative psychrophilic bacteria. The chief genera of this group are Pseudomonas and Achromobacter. These organisms cause slime formation, discoloration, and putrefaction of the product.

i. Honeycombing. A condition called honeycombing is found in canned tuna and salmon. It is caused by gas-forming bacteria present prior to canning. This is indicative of decomposed fish being utilized in the canning process. It is evidenced by small pitted holes in the surface flesh, which may extend through two or more layers. It can also be detected as a sharp taste during a sensory evaluation.

j. Pink or Red Oysters. A pink- or red-colored oyster indicates a deteriorative condition due to the growth of yeast at 0°F (-17.8°C) and below. The change in color starts as pinpoint specks. When the oyster is thawed, both the meat of the oyster and the liquid will become uniformly red. This can also be caused by the oysters eating small microscopic animals called dinoflagellates. Red pigments accumulate in the liver and give the oyster a pink or red color.

k. Green-Gilled Oysters. Green-gilled oysters represent another condition that may be observed. This condition is caused by the accumulation of a pigment in the gills and mantle. The bluish or greenish pigment is derived from certain types of diatoms. Diatoms are a family of minute algae upon which the oysters feed. The pigments are temporarily stored in the blood cells. These blood cells fill up the blood vessels of the gills and mantle. The color will be more evident in the gills than in any other area of the body.

l. Cotton or Milky Shrimp. A condition known as cotton or milky shrimp may be observed during the inspection of shrimp. It is due to parasitic protozoa (Microspordia). The flesh of the shrimp becomes soft and gelatinous and reminds one of a puffed-up piece of cotton or cottage cheese curds.

m. Fish Steaks and Fillets. Filleted and steaked fish are particularly susceptible to the deleterious effects of bad handling. This is because the naked fish provides an excellent medium for bacterial growth. Theoretically, a fillet carefully prepared from a fresh fish should be nearly sterile; all bacteria are initially present only on the exterior surfaces of the fish. However, filleting knives, tables and boards, filleter's gloves, wash water, and so forth, rapidly accumulate large populations of bacteria if proper sanitary precautions are not observed. A summary of the condition characteristics of fresh, stale, and putrid fish may be found in figure 3-1. Those characteristics that apply to fillets and steaks are marked with an asterisk.

FRESH

STALE

PUTRID

APPEARANCE*

Bright bloom

Dull

Dull - dry

ODOR*

Devoid of odor or odor is characteristic of species

Slight off-odor (fishy odor, trimethylamine)

Offensive odor (ammonia)

EYES

Bright, prominent, clear

Opaque, dull, sunken, red bordered

Greatly sunken, broken down, devoid of definition

or color

GILLS

Red, free of odor

Reddish-gray, pale yellow, slight odor

Dark brown, offensive odor

SCALES

Glisten, firmly adherent

Dull, loose, easily removed

Dry, loose, come off in hand

SURFACE SLIME

Clear, odorless, or creamy white

Devoid of color or dark, viscous, slight odor

Dry and very sticky, offensive odor

FLESH*

Firm, elastic, tight on bones, finger impressions do not remain

Soft, flabby, finger impressions remain

Withered, flabby, finger impressions remain

BLOOD*

Bright red, no odor

Dark brown, slight odor

Dirty brown, offensive odor

* Applies to fillets and steaks.

* Applies to fillets and steaks.

Figure 3-1. Condition classification: characteristics of fresh, stale, and putrid fish.

n. Surveillance Inspection. Microbial spoilage may develop in conjunction with other deteriorative or unacceptable conditions. If found during a surveillance inspection, all conditions should be reported to the accountable officer.

o. Summary of Microbial Spoilage. A summary of the microbial conditions of waterfood and spoilage organisms is found in figure 3-2.

PRODUCT

CONDITION

MICROORGANISM

FRESH FISH

Off-odor Fruity H2S odor

Pseudomonas, Vibrio, Proteus

Pseudomonas

Pseudomonas

Red growth Cheesy

Halobacterium Sporendonema Halophilic bacteria

OYSTERS

Serratia marcescens

SHRIMP

Off-odor

Pseudomonas

Figure 3-2. Microbial conditions of waterfoods.

Figure 3-2. Microbial conditions of waterfoods.

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  • samsa v
    What is bloom deteriorative condition?
    6 years ago

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