Shelf Life Prediction of Bread Sticks Using Oxidation Indices: A Validation Study
S. CALLIGARIS, S.D. PIEVE, G. KRAVINA, L. MANZOCCO, AND C.M. NICOLI
ABSTRACT: The aim of this study was to apply the protocol for the shelf life prediction of bakery products proposed by Calligaris and others (2007a) on bread sticks. The methodology comprises 4steps: (1) evaluation of the physical properties of fat; (2) performing the accelerated shelf life test; (3) evaluation of sensory acceptance limit and the relevant chemical index limit; (4) setting up the shelf life prediction model. The results allow validating the shelf life prediction methodology proposed. In fact, the peroxide number was found to be a representative index of the qualitydepletion of bread sticks during their shelf life. In addition, once again by accounting for the changes in the fat physical state, it is possible to set up a modified Arrhenius equation able to describe the temperature dependence of peroxide formation. Finally, a mathematical model to simply and quickly calculate the shelf life of bread sticks has been developed. Keywords: acceptance, bread sticks,lipid physical state, oxidation, shelf life modeling
akery products are one of the widest consumed product categories in the world with a global market in 2005 of about US $300 billions. Among the wide range of products countable in this food category, a big portion is dry shelf-stable foods such as biscuits, crackers, and bread sticks. Their quality depletion during storage is mainly caused bydifferent deteriorative events, among which lipid oxidation and the loss of crispness are the main phenomena. As well known, the 1st one is favored by the presence of oxygen, the 2nd one is due to the water absorption. From a technological point of view, the latter could be effectively prevented by the application of appropriate packaging solutions that, unfortunately, are not sufficient to avoidalso the oxidative reactions. Consequently, the lipid oxidation becomes the main deteriorative event leading to the quality depletion of dry bakery products. It is well known that oxidative reactions cause the formation of off-flavors accounting for the consumers’ rejection of the product (Shahidi and others 1987; Frankel 1993; Brewer and others 1999; Grosso and Resurreccion 2002). Consequently, aconsumer panel would be the most appropriate tool to determine when the food reaches the end of its life by sniffing the product. This approach conflicts with the industrial needs because it is very expensive and difficult to perform routinely. More useful for routine shelf life evaluation would be the identification of a chemical quality index, related to the sensorial acceptability, which could bemeasured by a quick and simple analytical method. The identification of such relationship is a key step in developing a simple and ready to use shelf life prediction model. To answer these practical problems, Calligaris and others (2007a) proposed a protocol to find out mathematical models for shelf life prediction of bakery products. In the case study considered, the authors evidenced that theperoxide value (PV ) could be a useful chemical index to monitor the loss of the sensory quality of the
product during storage. In fact, the PV changes were well correlated to sensory consumer acceptance. The availability of the mathematical relation between sensory acceptability and peroxide value, together with that of the temperature dependence of peroxide formation, wasexploited in developing a useful model allowing to simply and quickly calculating the shelf life of biscuits. Since lipid oxidation proceeds fairy slowly at room temperature, the further problem is to accelerate oxidation reactions in order to save time. Accelerated shelf life tests (ASLT) have been employed to predict the oxidative stability of lipid containing foods. Generally, temperature...