Quality Assurance for Sanitation 139tion or regulatory purposes because it is
directed at monitoring process control, not
individual product analysis. However, to be
familiar with the wholesomeness and overall
acceptability of each product, the preferred
procedure is to analyze and maintain control
charts on all products.
Sample size usually consists of three to
five specimens that serve as a representative
of the population sampled. Another guide-
line for sample size is the square root of the
total units, and, for large lots, an acceptable
size may be the square root of the total units
divided by 2. Daily sampling is necessary to
monitor process control effectively. Action
limits for finished products should be as out-
lined under the analysis program and should
be used in determining whether the process
conforms to the designated specifications. If
three consecutive samples exceed the maxi-
mum limit for contamination, production
should cease, with further cleaning.
Cumulative Sum (CUSUM) Control Charts
Data can be plotted where greater sensitiv-
ity in detecting small process changes is
required by use of the CUSUM chart. This
chart is a graphic plot of the running sum-
mation of deviation from a control value.
These differences are totaled with each sub-
sequent sampling time to provide the
CUSUM values. This monitoring technique
can be incorporated in sanitation operations
that require a higher degree of precision than
obtained from a regular statistical QC chart.
The CUSUM chart gives a more accurate
account of real changes, faster detection and
correction of deviation, and a graphical esti-
mation of trends. It enhances an optimum
process control for various applications.
Webb and Price (1987) suggested that the
CUSUM chart was not developed for multi-
ple levels and is not practical for use on pro-
duction processes that drift over an extended
period of time. If used, it is important that
the results of the CUSUM system be kept
current so that immediate corrective action
may be taken.
A personal computer can rapidly perform
the statistical computations and identify the
points that require corrective action, thus
reducing the burden of processing large
quantities of data. These data can be avail-
able to promptly expedite corrective actions,
project future performances, and determine
when and where preventive QC procedures
are necessary.Summary.................................................................................................
Product wholesomeness and uniformity
can be more effectively maintained through a
QA program that incorporates available sci-
entific and mechanical tools. Quality is con-
sidered to be the degree of acceptability by
the user. These characteristics are both
measurable and controllable. The major
ingredients needed for a successful QA pro-
gram are education and cooperation. The
HACCP approach can be incorporated in a
QA program because it applies to a zero-
defects concept in food production. Effective
surveillance of a QA program can detect
unsanitary products and variations in pro-
duction. Statistical QC techniques make
inspection more reliable and eliminate the
cost of 100% inspection. The principal tool
of a statistical QC system is the control
chart. Trends of control charts provide more
information than do individual values. Val-
ues outside the control limits indicate that
the production process should be closely
observed and possibly modified.