Fundamental Food Microbiology, Third Edition - Fuad Fathir

NORMAL MICROBIOLOGICAL QUALITY OF FOODS AND ITS SIGNIFICANCE 45
Low-heat-processed red meat and poultry products include perishable cured or
uncured products that have been subjected to heat treatment to ca. 160�F (70°C) ,
packaged aerobically or anaerobically, and stored at refrigerated temperature. They
include products such as franks, bologna, lunchmeats, and hams. The products,
especially those packaged anaerobically and cured, are expected to have a long
storage life (50 d or more). The microbial sources before heat treatment include the
raw meat, ingredients used in formulation, processing equipment, air, and personnel.
Heat treatment, especially at an internal temperature of 160�F or higher, kills most
microorganisms, except some thermodurics, which include Micrococcus, some
Enterococcus, and maybe some Lactobacillus and spores of Bacillus and Clostridium.
The microbial level can be 10 1–2 / g. Following heating, the products, some of
which are further processed (such as removing casing or slicing) come in contact
with equipment, personnel, air, and water before final packaging. Different types of
bacteria, yeasts, and molds, including pathogens, can enter these products, depending
on the conditions of the processing plants. Although the initial bacterial level normally
does not exceed 10 2 /g, some of them can be psychrotrophic facultative anaerobic
and anaerobic bacteria (Lactobacillus, Leuconostoc, some coliforms, Serratia,
Listeria, Clostridium spp.). During extended storage in vacuum or modified-air
packages, even from a low initial level, bacterial population can rise and adversely
affect the safety and shelf life of products. This is aggravated by fluctuation in storage
temperature and in products having low fat, high pH, and high A w. 1–4
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III. RAW AND PASTEURIZED MILK
Raw milk can come from cows, buffalo, sheep, and goats, although the largest
volume comes from cows. Pasteurized or market milk includes whole, skim, lowfat,
and flavored milks, as well as cream, which are heat treated (pasteurized)
according to regulatory specifications. 1,2,5 Milk is high in proteins and carbohydrates
(lactose), which many microorganisms can utilize for growth. Because both raw
milk and pasteurized milk contain many types of bacteria as predominant microorganisms,
they are refrigerated; yet they have limited shelf life.
In raw milk, microorganisms come from inside the udder, animal body surfaces,
feed, air, water, and equipment used for milking and storage. The predominant types
from inside a healthy udder are Micrococcus, Streptococcus, and Corynebacterium.
Normally, raw milk contains