Methods for food shelf life determination and prediction - Oxidation in Foods and Beverages and Antioxidant Applications - page 202

Table 9.4 Mean peroxide value corresponding to different percentages of consumer
rejecting the biscuits stored at 20 ëC

Consumers rejecting Peroxide value (meqO 2 /kg fat )

the sample (%)

95% lower limit Estimated 95% upper limit

10 4.9 6.4 8.9

30 8.6 10.9 14.4

50 12.9 15.6 18.1

70 18.4 21.7 25.7

From Calligaris et al. (2007a) with permission.

indicator of consumer acceptability. Peroxide values corresponding to different
acceptability limit were thus calculated (Table 9.4).
Further examples demonstrating the possible application of this approach
have been reported by Hough et al. (2002), Gambaro et al. (2004), Garitta et al.
(2004) and Manzocco and Lagazio (2009) with reference to different food
products.
It must be noted that this approach only leads to oxidative index values
corresponding to consumer acceptability limits at a specific storage temperature,
which is chosen to apply the methodology reported in Fig. 9.3. At the moment
there is no literature indication that an oxidative index determined at one
temperature can be successfully used at temperatures other than those used in the
initial experiment.

9.5 Shelf life testing
As shown in Fig. 9.1, once an appropriate oxidative indicator has been
identified, it is necessary to estimate the length of time needed to reach some
critical value. This step, generally defined as shelf life testing, implies the
continuous monitoring of the changes of the oxidative indicator during storage
of food under controlled environmental conditions. Data relevant to the
evolution of oxidation during storage are then modelled to obtain proper
parameters describing/predicting the oxidation kinetics. The latter are necessary
to obtain the shelf life once knowing the acceptability limit.
Two strategies of shelf life testing can be pursued depending on the expected
product life time:

1. shelf life testing under actual storage conditions for perishable foods;
2. shelf life testing under accelerated storage conditions for shelf-stable
products.

While the former is based on the direct measure of product shelf life according
to its usual storage conditions, the latter implies stability tests to be carried out
under environmental conditions able to speed up quality loss.