Study of Meat Shelf-Life Markers and Food Quality Through Different Instrumental Analytical Methods

Shelf-life is defined as the time during which a food product remain safe, comply with label declaration of nutritional data and retain desired sensory, chemical, physical and microbiological characteristics when stored under the recommended conditions [1]. Shelf-life is a function of time, environmental factors and susceptibility of product to quality change [2]. The study of food shelf-life is becoming increasingly important for two main reasons: the need to furnish safe food to a continuously growing population and the need to reduce the food waste. In fact, an increase of food production to supply the needs of the population is not sustainable from an ecological point of view [3] and it is also inevitably correlated to food loss and waste. The Food and Agriculture Organization (FAO) reports that the food waste in Europe and in North America is 95–115 kg/year per capita, and the extent of food loss and waste globally reaches approximately 1.3 billion tons per year [4]. While food losses are mainly related to food-processing [5], food waste is related to food shelf-life as it occurs during distribution and consumption processes in the food-chain [6]. In fact, the distribution of food products under inadequate conditions, such as high temperature or humidity, that is one of the causes of the shortening of shelf-life [7-9], or the delay in the consumption after the expiring date, that gives to the food product an uncertain safety [10, 11], are responsible for the wasting of a percentage of perishable foods that ranges from 15% (mainly for damage and spoilage) [12] to 35% (for inadequate temperature) [13]. By the consequence, monitoring food shelf-life means monitoring the degree of food spoilage and therefore reducing food waste [14]. However, monitoring food shelf-life is not simple as deterioration processes can be evidenced by several attributes that are product, consumer and market specific [15, 16]. In foods with long shelf-lives, the end of the acceptability for the consumption is usually determined through the evaluation of nutritional and organoleptic properties [17], while that of high perishable foods is mainly detected through the loss of sensorial properties or changes in the organoleptic characteristics (flavour, colour) [18, 19]. The study of food spoilage degree can be carried on through sensorial analyses, which are based on the use of survival analysis methodologies [20] to evaluate the consumer rejection probability level, or through instrumental measurements, which are often related to sensory attributes. As reported in Table 1, several attributes related to food shelf-life have been regulated and used as markers of shelf-life in diverse food products. Most times, the study of microbial spoilage is the most reliable attribute related to food spoilage and it is directly connected to a loss of sensorial attributes [21]. However, monitoring food shelf-life is not simple as deterioration processes can be evidenced by several attributes that are product, consumer and market specific [15, 16]. In foods with long shelf-lives, the end of the acceptability for the consumption is usually determined through the evaluation of nutritional and organoleptic properties [17], while that of high perishable foods is mainly detected through the loss of sensorial properties or changes in the organoleptic characteristics (flavour, colour) [18, 19]. The study of food spoilage degree can be carried on through sensorial analyses, which are based on the use of survival analysis methodologies [20] to evaluate the consumer rejection probability level, or through instrumental measurements, which are often related to sensory attributes. As reported in Table 1, several attributes related to food shelf-life have been regulated and used as markers of shelf-life in diverse food products. Most times, the study of microbial spoilage is the most reliable attribute related to food spoilage and it is directly connected to a loss of sensorial attributes [21]. However, monitoring food shelf-life is not simple as deterioration processes can be evidenced by several attributes that are product, consumer and market specific [15, 16]. In foods with long shelf-lives, the end of the acceptability for the consumption is usually determined through the evaluation of nutritional and organoleptic properties [17], while that of high perishable foods is mainly detected through the loss of sensorial properties or changes in the organoleptic characteristics (flavour, colour) [18, 19]. The study of food spoilage degree can be carried on through sensorial analyses, which are based on the use of survival analysis methodologies [20] to evaluate the consumer rejection probability level, or through instrumental measurements, which are often related to sensory attributes. As reported in Table 1, several attributes related to food shelf-life have been regulated and used as markers of shelf-life in diverse food products. Most times, the study of microbial spoilage is the most reliable attribute related to food spoilage and it is directly connected to a loss of sensorial attributes [21]. As food is a complex matrix, it is difficult to select just one marker (called also limiting factor) to monitor the shelf-life. For this reason, several approaches have been developed to study more than one limiting factor to have an overall idea of spoilage process. With regard to this, MathematicaR (Wolfram Research, Champaign, IL) is a new interactive program, developed by Peleg and Normand (2015) that combine two limiting factors simultaneously to evaluate food shelf-life [35]. Another approach concerns the use of a single index called global stability index (GSI), developed by Achour (2006), which combine sensory, chemical and microbiological attributes to evaluate food shelf- life [36]. Even if GSI has been used to study the shelf-life of fresh products and fish [37- 40], its limitation is related to the lack of standard procedures to assign the values for each limiting factor. One more strategy used to study food shelf-life is based on fingerprinting kinetics and it was developed by Grauwet et al. (2014) [41]. This approach allows to identify the most important markers of shelf-life for a specific food product by screening the modifications in the food product, due to degradation processes, and selecting the most important markers involved in the degradation process. Then, it allows to connect the selected markers to specific spoilage reactions though a multivariate analysis. This technique allows to have an overall idea of food spoilage process and it has been used to study the shelf-life of fruit/vegetable juices and purees [42-46]. The study of food shelf-life, the identification of a marker of shelf-life and the regulation on the minimum level to be respected for that specific marker is essential to establish useful information for the consumer, such as the expiration date. The expiration date represents the time needed for the chosen quality attribute to reach its unacceptable level under specific storage conditions. The expiration date is clearly visible on the packaging of the food product and reported as “use by date” or “best before” [47]. An accurate match between the expiration date and the end of the shelf-life of the food product is found, if the storage conditions have been respected from the dealers and the consumers [48-50]. However, adequate storage conditions are not often respected, especially regarding the temperatures of refrigerators [51-53] or improper packaging which slows the air-flow with subsequent increase of the temperature [52, 54]. This leads to a mismatch between the expiration date and the effective spoilage degree of the food product. Moreover, these evidences have pointed out the ongoing process according to which the expiration dates will have always less importance [55], giving way to new technologies that are able to provide a real-time shelf-life estimation of food products.