Degradation Markers in Nutritional Products a Review

Research Article

Austin J Anal Pharm Chem. 2014;1(1): 1005.

Degradation Markers in Nutritional Products a Review

Sochr J, Cinkova K and Svorc L*

Department of Chemical and Food Technology, Slovak University of Technology, Slovak Republic

*Corresponding author: :Svorc L, Institute of Analytical Chemistry, Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, 812 37 Bratislava, Slovak republic.

Received: June 29, 2014; Accepted: July 08, 2014; Published: July 08, 2014


The main objective of the present review is to develop a brief overview of the current state of the knowledge on the analytical determination of oxidation and/or degradation parameters in nutritional products. Basically, since it is one of the major causes of food quality deterioration, and it has been a challenge for manufacturers and food scientists alike, lipid oxidation has traditionally been the most studied process throughout the history. There are many analytical methods to perform the detection of changes in food quality, focusing on the determination of the formation of oxidation products or on the changes in the standard profile of specific compounds. In addition, sensory analyses to identify oxidative changes in foods are also common. However, it is not the only parameters to measure the oxidation of food. Proteins and carbohydrates are also susceptible to oxidation; and therefore, many undesirable and/or harmful metabolites can also be found in food after this type of degradation that food industry must necessary control. The proposed summarized review will focus on both oxidation processes in order to better understand the evolution throughout the history of food control.

Keywords: Nutritional product; Oxidation; Degradation; Analysis


In general, the oxidation of food stuffs is a process that must be avoided. However, the process occurs naturally when food is exposed to air and it is potentiated by heat, light, chemical catalysts or enzymatic processes. The oxidation causes the loss of nutritional value of food and changes the chemical composition. For example, oxidation of fats and oils leads to rancidity and in fruits it can result in the formation of compounds which discolor damaging the product.

The food alterations could deteriorate the quality of the product and also generate undesirable compounds with direct consequences on human health. There are many reports published in the scientific literature about the possible toxicity of certain metabolites generated from lipid oxidation such as cholesterol oxidation products; COPs, commonly known as oxy sterols; OS [1,2]; and phytosterol oxidation products; POPs; which have unhealthy effects at higher concentrations. Cytotoxicity, atherogenesis, mutagenesis, carcinogenesis changes in cellular membrane and inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase, HMG-CoA reductase, activity have been widely described [3-6].

Therefore, it is mandatory to control the oxidation processes using the technology available. Throughout the history, several analytical methods have been proposed to keep under control the oxidation of nutritional products. There are very different techniques that can be applied depending on the final objective and the product under study. The oxidation parameters to measure can be classified in three important groups depending of the sample: lipids, proteins or carbohydrates. Another classification could be done taking into account the technique used to control the oxidation: chemical or sensory methods. Finally, a third classification could be showed comparing two modes: general oxidation or determination of target compounds.

This summary review consists in a globalized approach to know, from an analytical point of view, the evolution in food control in terms of oxidation parameters. In addition, the methods and techniques that are commonly employed today to determine the rate of oxidation of food are presented in more detail.

Lipid Oxidation

Lipids are an important component of food being also used in a large amount of industrial applications. Lipids in food, either naturally occurring or added exogenously are used as nutrient and also provide a heat transfer medium for food processing and render desirable texture and flavour to the products. They are one of the major and essential macronutrients required for growth and maintenance of living organisms. However, overconsumption of lipids, especially certain saturated lipids and trans fats, has been associated with diseases such as obesity, hypertension, cardiovascular disease or cancer [3,7-10], mainly when these lipids are oxidized generating other compounds. Although there are others hypothesis that differ regarding the issue of that fats are the unique responsible of cardiovascular disease [11,12].

Lipid oxidation is an important cause of deterioration in quality of food both during manufacturing and product shelf life, and negatively affects the integrity of biological systems. The oxidative changes cause development of off-flavors, loss of nutrients and bioactives, and even the formation of potentially toxic compounds originating products unsuitable for the human consumption.

The overall mechanism of lipid oxidation consists of three phases: the initiation, with the formation of free radicals; the propagation, with the free-radical chain reactions; and the termination, with the formation of stable non-radical products.

The most important lipids involved in the oxidation process are the unsaturated fatty acid moieties, oleic, linoleic and linolenic. Lipid peroxidation generates a large number of by-products, including breakdown molecules resulting from cleavage of the oxidized fatty acyl chain as is shown in Figure 1. The rate of oxidation of fatty acids increases with the degree of unsaturation. The free radicals reactions are thermodynamically difficult, for this reason the production of the first few radicals mandatory must occur by some catalytic means such as hydro peroxide decomposition, light and heat exposure and metal catalysis. In addition, auto oxidation is the most common process. It is defined as the spontaneous reaction of lipids with atmospheric oxygen through a chain reaction of free radicals (Figure 1).