Elsevier

Food Chemistry

Volume 190, 1 January 2016, Pages 122-127
Food Chemistry

Analytical Methods
Authentication of canned fish packing oils by means of Fourier transform infrared spectroscopy

https://doi.org/10.1016/j.foodchem.2015.05.064Get rights and content

Highlights

  • ATR-FTIR to assess the genuineness of the packing media of canned fish.

  • PLS-DA can differentiate olive oil from seed oils regardless the type of fish canned.

  • Sunflower oil cannot be differentiate from oils labeled as “vegetable oil”.

  • No interfering effect from fish lipid transference has been observed.

Abstract

The authentication of packing oil from commercial canned tuna and other tuna-like fish species was examined by means of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and chemometrics. Using partial least squares discriminant analysis (PLS-DA), it was possible to differentiate olive oil from seed oils. Discrimination of olive oil from high-oleic sunflower oil was possible, despite the latter having a degree of unsaturation more similar to olive oil than to sunflower oil. However, in the samples analyzed, sunflower oil could not be differentiated clearly from those labeled with the generic term “vegetable oil”. Furthermore, the authentication of extra virgin olive oil, although more difficult, could be achieved using ATR-FTIR spectroscopy. The method could be applied regardless of fish type, without interference from fish lipids.

Introduction

Interest in fish consumption has increased in recent years due to the wide range of health benefits associated with the high polyunsaturated fatty acids (PUFAs) content. In addition to fresh fish, canned products enable delayed consumption of this otherwise perishable food. Canned tuna is one of the most widespread and recognizable fish commodities in the world, and oil is frequently adopted as a liquid medium. In fact, oil has a preserving effect and helps make the product more palatable. Among the different types of oil, the most commonly used in canning are: olive oil (OO, made up of refined olive oil blended with virgin oil, apart from ‘lampante’ oil, in an undefined ratio) and refined seed oils (RSOs). The most expensive extra virgin olive oil (EVOO, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes) is reserved for tuna due to the higher commercial value of this fish. In general, the price of canned fish in OO is higher than fish in RSOs, (sunflower or soybean oils), which are commonly labeled as “vegetable oil”. Furthermore, the presence of OO is usually highlighted in the labeling by the producers because its consumption is associated with a healthy diet. European Commission Regulation No. 1536/92 (European Commission, 1992), laying down common marketing standards for preserved tuna and bonito, establishes that if the covering medium used forms an integral part of the trade description, (i.e. name of the product includes the description ‘in olive oil’), only OO can be used, excluding all other oils. In addition, the introduction of new EU legislation (European Parliament, 2011) concerning food information for consumers, which took effect in 2014, brings important changes in the labeling of foodstuffs. Regarding processed foods containing vegetable oil as an ingredient, the new regulation states the type of oil employed must be indicated on the package. Up to now, it has been common practice to label the oil with the generic term “vegetable oil”. Consequently, there is a growing need to develop methodologies for industry and regulators to verify the type of oil used (Osorio, Haughey, Elliott, & Koidis, 2014). Few studies assessing the genuineness of the liquid medium in production of in-oil canned fish have been reported. Of those that have been published, the first was designed to assess the genuineness of oil used as medium for canned tuna, mackerel and sardines by analysis of fatty acid composition (Cerma and Remoli, 1966, Remoli and Doro, 1968, Remoli and Doro, 1970). Similarly, the percentage of unsaturated fatty acids trans isomers has been evaluated to test the genuineness of the oil for canned sardines, tuna and mackerel (Bizzozero and Carnelli, 1996, Cavallaro et al., 1996). Triglycerides profiles were proposed as a more reliable tool by Vittucci, Pierri, and Maffei (1999). These studies stressed the difficulty of assessing whether the oil, used as liquid medium in canned fish, was genuine because of lipid exchange between the fish and oil. Thus, the fact that fish releases lipids, and trans linoleic and trans linolenic acids can affect features essential in determining whether the oil is genuine (Vittucci et al., 1999). To address this problem, Rossi and co-workers reported the sterol composition could contribute when assessing oil authenticity (Rossi, Colonello, & Alamprese, 2001). In recent studies, more emphasis has been given to the evaluation of oil quality, particularly aspects such as the extent of oxidative and hydrolytic degradation (Caponio et al., 2003, Caponio et al., 2011).

IR spectroscopy is a rapid and non-destructive technique for the authentication of food samples. Analysis of a food sample using the MIR spectrum (4000–400 cm−1) reveals information about the molecular bonds present and can, therefore, give details of the types of molecules present in the food. This technique is suitable for use in an industrial setting due to its ease of use and the relatively low financial cost of obtaining and running the equipment. Different types of foods have been tested for adulteration using IR spectroscopy: wine samples have been differentiated on the basis of geographical and varietal origin (Roussel, Bellon-Maurel, Roger, & Grenier, 2003); MIR and chemometrics detected adulteration of apple juice with beet syrup and cane syrup (100% and 96.2% correct, respectively, Sivakesava, Irudayaraj, & Korach, 2001); and adulteration of honey samples with sugar solutions at 14% w/w was detected using MIR and PLS (Kelly, Downey, & Fouratier, 2004). Extensive research has been performed regarding virgin olive oil adulteration because of its especial characteristics of high quality and high price commodity (Aparicio et al., 2013, Nunes, 2014). Thus, several models of principal component analysis (PCA) (Lai, Katherine Kemsley, & Wilson, 1994), stepwise linear discriminant analysis (SLDA) (Baeten et al., 2005) and partial least squares discriminant analysis, PLS-DA (Obeidat, Khanfar, & Obeidat, 2009) have been proposed to identify the presence of different vegetable oils in OO, mainly EVOO. Quantification of different adulterants in OO have also been approached – using FTIR and PLS (Gurdeniz and Ozen, 2009, Lerma-Garcia et al., 2010, Maggio et al., 2010, Tay et al., 2002). Furthermore, recently, we have proposed a methodology for quantification of OO in blends that meet specific EU legislation concerning commercialization and labeling of OO products (de la Mata et al., 2012). Here, we will evaluate for the first time the potential use of FTIR in combination with chemometrics to assess the authenticity of the oil added to canned fish.

Section snippets

Samples

Samples of in-oil canned fish (90) were purchased from different retailers (10) in Spain. They included different brands of canned tuna and other tuna-like species in a variety of olive (48) and seed (42) oils. A more detailed description of the samples is provided in Table 1. According to EU Regulation 1536/92 (European Commission, 1992), the light tuna label refers to Thunnus albacares, and the label generically denominated as “tuna” may include any Thunnus or similar species (e.g.,

Infrared spectra of fish flesh and packing oils

The ATR-FTIR spectra of different canned tuna-like fishes and different oils are shown in Fig. 1.

The infrared spectrum of fish flesh was dominated by the absorption bands characteristics of proteins at 3270 cm−1 (Nsingle bondH stretching, amide A), 1621 (Cdouble bondO stretching, amide I) and 1539 cm−1 (Nsingle bondH bending coupled with Csingle bondN stretching, amide II). The absorption bands of water, which usually accounts for about 60% of the weight of fresh fish muscle and is tightly bound to the proteins in the structure (Rasmussen

Conclusions

Information from the ATR-FTIR spectra of oil media in canned fish can be used for authentication of the botanical origin of the oil regardless of the type of fish. A clear distinction between oils rich in monounsaturated fatty acids and oils rich in polyunsaturated fatty acids was achieved easily using PCA. In addition, using PLS-DA, it was also possible to differentiate accurately HOSO from the rest and, even, to distinguish EVOO from OO with reasonable prediction performance. On the contrary,

Acknowledgments

The authors acknowledge the Andalusia Regional Government (Consejería de Innovación, Ciencia y Empresa) for financial support through project P07-FQM-02667 and PAIDI Research Group FQM363. J.P. De la Rosa is also grateful to the University of Jaén for a Beginning Research grant.

References (30)

  • S. Roussel et al.

    Authenticating white grape must variety with classification models based on aroma sensors, FT-IR and UV spectrometry

    Journal of Food Engineering

    (2003)
  • A. Tay et al.

    Authentication of Olive Oil Adulterated with Vegetable Oils Using Fourier Transform Infrared Spectroscopy

    LWT – Food Science and Technology

    (2002)
  • V. Baeten et al.

    Detection of the presence of hazelnut oil in olive oil by FT-Raman and FT-MIR spectroscopy

    Journal of Agricultural and Food Chemistry

    (2005)
  • N. Bizzozero et al.

    Fatty acid composition and trans unsaturation of the covering oil of canned mackerels and tunas

    Industrie Alimentari

    (1996)
  • F. Caponio et al.

    Use of HPSEC analysis of polar compounds in the ascertainment of the degradation level of oils utilised as liquid medium in canned tuna

    Rivista Italiana delle Sostanze Grasse

    (2002)
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