Plant sanitation - Gracey's Meat Hygiene - page 94

can be a disadvantage if excessive rinsing is required or
an advantage for reasons of visibility and procedural
monitoring. The foam level can easily be controlled in a
multi-injector satellite station (described in a later sec-
tion) so this feature can be used as required.

in fatty foods. The risk is compounded by the presence of
chlorine, even at low levels in factory water. Chlorocresols
and chlorophenols may be formed which can taint meat
at low levels, parts per billion (ppb).
Considering all of the information in this section on
disinfection, the important points for industry at present
are to:
• Select the right product type for a particular appli-
cation
• Use freshly diluted product (if the product type
demands an aqueous solution)
• Ensure the correct concentration can be routinely
achieved and validate it
• Apply the product at the right point within the total
hygiene procedure
• Ensure sufficient contact time (determined by prod-
uct type/standard required)

Disinfectants: Design and choice
The method of kill and the point of attack on the defences
of micro-organisms may be different in each case. Unless
carefully formulated, disinfectants could have weak-
nesses at lower temperatures or against some more diffi-
cult-to-kill bacteria such as pseudomonads . This could
be critical, for example, when disinfecting a chill.
Well-formulated disinfectants may employ several dif-
ferent biocidal components, often with surfactants and
other agents to help in the killing action. This also helps
eliminate the possibility of adaptation or even resistance
developing among the population of micro-organisms.
Development of resistance to antibiotics is well docu-
mented and increasingly observed in the medical and
veterinary fields (Soonthornchaikul et al. , 2005). To date,
a similar resistance pattern to biocides and disinfectants is
not readily seen in industrial applications such as food
plant disinfection. However, different susceptibilities have
been described for culturable and viable non-culturable
(VNC) forms of Campylobacter , against disinfectants at
low in-use levels (Rowe et al ., 1998). There is increasing
work in this area particularly looking for evidence of
antibiotic-induced cross-resistance to standard disinfect-
ants and vice versa, both in clinical practice (Russell, 2002)
and in the food production system (Doyle et al ., 2006).
Disinfectants can be affected by residues of detergents
left on surfaces, perhaps owing to inadequate rinsing.
Anionic surfactants in the detergent may neutralise the
cationic surfactant of 'quats, rendering them ineffective.
Disinfectants should be chosen in conjunction with
the supplier, taking into full account the surface materi-
als to be disinfected; the soil residues likely to be present
after cleaning; the safety to operators and product; the
specific organisms, if any, to be controlled; the ambient
and solution temperature; and the timescale (rapid or
residual) required. Cleaning and disinfection for some
applications may be adequately combined into one oper-
ation using a sanitiser, which has the action of both a
detergent and a disinfectant. Usually, this is a quat- or
amphoteric-based neutral or mildly alkaline product for
manual use. However, the one-stage product approach,
while time-saving, does not give as consistent or as effec-
tive a final result as the two stages executed separately.
Under no circumstances should phenolic, pine or
other highly perfumed disinfectants be used in a food
plant, even in the offices. The risk of taint is high, even
from very small airborne concentrations and especially

Disinfectant kill rates can be routinely assessed via
standard European Norm (EN) disinfection assessment
tests, and although they 'mimic' the real environment,
they are a controlled and standardised way of showing
differences between disinfectant products (BS EN 1276,
2009; Maillard, 2005). Accordingly, they can be used as
part of the selection criteria earlier.
Disinfection assessment tests are a good source of
information about the basic efficacy of a biocidal mole-
cule or formulated disinfectant product within certain
test parameters. These tests measure kill rate (a mathe-
matical log reduction of the viable members of a micro-
bial population of known origin and size) while taking
into account performance-limiting factors within the
proposed use environment such as low temperatures and
residual soiling. The effective in-use concentrations are
then usually established at hundreds or thousands of
ppm of biocidal molecules. This approach ensures that
the final recommended in-use concentration of a disin-
fectant product is significantly above (often ×10 or ×20)
the known minimum inhibitory concentration (MIC) of
the individual biocidal molecules or disinfectant formu-
lation. The MIC is the value of a standard laboratory test
at which an antimicrobial agent will prevent growth of a
specific micro-organism.
All of these points together are designed, in respect of
current understanding, to ensure that the targeted
micro-organisms are removed/killed and reduce the risk
of temporary adaptation or even permanent resistance
within a species or population.

Hygiene equipment and application methods
Detergents and disinfectants can be applied in a number of
different ways, dictated by the nature of the cleaning task.