Elsevier

Food Chemistry

Volume 302, 1 January 2020, 125327
Food Chemistry

Effect of tomato (Solanum lycopersicum L.) lycopene-rich extract on the kinetics of rancidity and shelf-life of linseed (Linum usitatissimum L.) oil

https://doi.org/10.1016/j.foodchem.2019.125327Get rights and content

Highlights

  • The effect of tomato lycopene extract (TLE) on linseed oil shelf life was evaluated.

  • 80 mg lycopene/kg oil showed the same induction time at 110 °C of 200 mg BHT/kg oil.

  • TLE addition slowed oil degradation without changing the mechanism.

  • Rancidity followed first order kinetics during storage at 40–60 °C until 90 days.

  • TLE increased oil shelf-life at 25 °C by 31% (Rancimat) and 42% (kinetics).

Abstract

The effect of tomato lycopene-rich extract (TLE) addition on shelf-life of linseed oil was evaluated. Linseed oil was extracted by cold pressing and TLE by supercritical CO2. Linseed oils with and without TLE addition were characterized for moisture, color, refractive index, fatty acid composition and antioxidants. Adding TLE to 80 mg lycopene/kg oil improved linseed oil stability, showing the same induction time at 110 °C (by Rancimat) of control linseed oil with 200 mg/kg butylhydroxytoluene. The increase of free fatty acid, peroxide value, p-anisidine value, K232 and K268 at 40, 50, and 60 °C until 90 days followed first-order kinetics. Rancidity rate augmented with temperature. TLE addition slowed oil degradation without changing the mechanism since the Arrhenius lines were parallel. Mean Ea were respectively 38.2, 24.7, 38.0, 38.2, 41.5 kJ/mol. TLE addition increased linseed oil shelf-life by 31% (Rancimat) and by 42% (stability kinetics during storage).

Introduction

Flax (Linum usitatissium L.) has been cropped by man for thousands of years (Tańska, Roszkowska, Skrajda, & Dąbrowski, 2016). Currently it is cultivated for a dual purpose: to obtain vegetable fiber from the stem and to extract oil from the seeds. According to FAOSTAT (2014), 686 498 t of linseed oil were produced worldwide; the largest producer is China (25%), followed by Belgium (19%), United States (17%), Germany (8%), Ethiopia (7%) and India (7%).

Linseed or flaxseed oil has several industrial purposes, such as production of paint and floor covering (linoleum), additive in PVC plastics, coal-agglomerating agent, etc. The growing interest in the utilization of linseed oil as food is due to its high content of two polyunsaturated fatty acids (PUFA), α-linolenic acid (ALA; omega-3) and linoleic acid (LA; omega-6). The α-linolenic acid varies between 49 and 64% of total fatty acids and the linoleic between 15 and 17% (Shadyro, Sosnovskaya, & Edimecheva, 2017). Several studies have been carried out to test the benefits deriving from the consumption of PUFA, which contribute to prevent the onset of cardiovascular diseases, cancer and inflammation (Shadyro et al., 2017). However, the high degree of α-linolenic acid unsaturation implies a great susceptibility of linseed oil to oxidation during production and storage (Tańska et al., 2016), leading to significant deterioration of sensory characteristics and drastic reduction in nutritional value, thus limiting its access to the food and pharmaceutical markets.

The protection of vegetable oils, especially polyunsaturated oils, from oxidation is thus fundamental to guarantee an extended shelf-life. Numerous studies evaluated the effectiveness of natural and synthetic antioxidants to delay oxidative phenomena in vegetable oils (e.g. Wani, Sogi, Singh, & Götz, 2013), and in particular in linseed oil (Shadyro et al., 2017). Synthetic compounds such as butylhydroxyanisole (BHA), butylhydroxytoluene (BHT), and tert-butyl-hydroquinone (TBHQ) are widely used antioxidants due to their low cost, high stability and efficacy; a maximum amount of 200 mg/kg oil of any combination of these antioxidants is allowed (Codex Alimentarius, 2017a). However, possible toxicological effects on human health have been observed and some countries (e.g. Japan, Romania, Sweden, and Australia) banned their utilization (Ghatak & Sen, 2017).

In recent years there is a steady growth in studies dealing with the improvement of oxidative stability of linseed oil through the addition of natural antioxidants. Michotte et al. (2011) demonstrated that myrecitin was the phenolic compound that most reduced the production of primary oxidation products. Interestingly, Van Ruth, Shaker, and Morrissey (2001) decreased the amount of primary oxidation products by 30% and of secondary products by 99% with the addition of soybean methanol extracts.

Another promising antioxidant candidate is lycopene (Nour, Corbu, Rotaru, Karageorgou, & Lalas, 2018), an acyclic carotenoid abundant in tomatoes and tomato-based products, accounting for more than 85% of all lycopene sources in the diet, but present also in guava, cranberry, peaches, pink grapefruit, apricot, watermelon and papaya (Kaur & Kaur, 2015). Lycopene is a fat-soluble pigment able to quench damaging free radicals, especially the most aggressive reactive oxygen species (the singlet oxygen) and has antioxidant and antitumor properties (Kaur & Kaur, 2015).

Therefore, aim of this work was to investigate the kinetics of rancidity (hydrolysis, primary and secondary oxidation) as well as the shelf-life of linseed oil before and after the addition of tomato lycopene-rich extract (TLE).

Section snippets

Materials and methods

Seeds of brown flax variety were procured from the market of Ayacucho (Peru) and tomatoes cv. Perseo from the Universidad Nacional Agraria La Molina (Lima, Perú).

Chemical composition of flax seeds and dried tomato

Moisture, protein, lipid, ash and carbohydrate content of flax seeds (7.38 ± 0.09, 17.24 ± 0.02, 42.12 ± 0.47, 3.32 ± 0.01, and 29.94 ± 0.53 g/100 g, respectively) were similar to the data (7.7, 20.0, 41.0, 3.4, and 29.0 g/100 g, respectively) reported by Morris (2007) for brown flaxseed varieties from Canada.

The moisture, protein, lipid and ash concentrations of dried tomato were 4.81 ± 0.39, 12.13 ± 0.06 1.29 ± 0.27, and 10.73 ± 0.48 g/100 g, similar to the results reported for tomato dried

Conclusions

The presence of 80 mg lycopene/kg linseed oil led to the same induction time at 110 °C (by Rancimat) obtained using 200 mg/kg of the antioxidant artificial BHT. Significant differences were found between lycopene extract-enriched and pure linseed oil for color. TLE addition significantly increased linseed oil antioxidant capacity (ABTS test) from 2.48 to 3.33 μmol TE/g. During storage, the kinetics of formation of all rancidity parameters were first-order. The rate constant k increased with the

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

Financed by the Fondo Nacional de Desarrollo Científico, Tecnológico y de Innovación Tecnológica (FONDECYT), Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica (CONCYTEC), Perú, contract N° 126 – 2015 – FONDECYT. We thank Prof. Dimitri Fessas and Dr. Andrea Brandolini for their comments and suggestions.

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