ROBERTA DA SILVEIRA

Título da Dissertação: DETERMINAÇÃO DE FRAUDE EM AZEITE DE OLIVA EXTRA VIRGEM POR ESPECTROMETRIA DE MASSAS

Orientadora: Prof. Dr. Jesuí Vergílio Visentainer

Data da Defesa: 23/02/2018

RESUMO GERAL

INTRODUCTION. Nowadays consumers are particular concerned about products quality, valuing and prioritizing healthy food, and for this reason, lard and sebum are being replaced by edible vegetable oils, with special emphasis on olive oil (Olea europaea) due to its combination of enjoyable flavor and nutritional benefits. Owing to health appeal, desirable characteristics and limited production, extra virgin olive oil (EVOO) has elevated commercial value, becoming focus of intentional adulteration. Among these, the most common includes the addition of low cost edible vegetable oil such as refined soybean oil (SO), which is the second most consumed vegetable oil around the world representing the main culture in Brazil. The price difference between EVOO and SO could be a technique to industries profit from the addition of low cost oils to EVOO.
AIMS. This work aims to apply simple methodologies established by Codex Alimentarius claiming to ensure quality criteria, such as free acidity and absorbency in ultraviolet for later comparison with label information, plus ensures purity criteria through fatty acid composition. The results from all three analyses adopted by food industry were compared to a new developed method to identify and quantify addition of SO in EVOO, detecting a lipid marker present only in SO from triacylglycerol (TAG) composition obtained by ESI-MS direct infusion. Subsequently, all four methodologies were applied in commercial samples and compared in order to demonstrate that the current methodology adopted by industry to guarantee purity and quality of EVOO is not sufficient to detect small adulteration.
MATERIAL AND METHODS. Eight bottles of EVOO and two cans of commercial blends of SO and EVOO, as well as SO were acquired from local market of Maringa – PR, Brazil, in addition one sample with international certificate identified as P was used as standard. Quality and purity criteria were carried out according to International Olive Council (IOC). TAGs were detected by ultra performance liquid chromatography (UPLC) Acquity H-class system coupled to a triple quadrupole mass spectrometer Xevo TQDTM (MS) equipped with electrospray ionization (ESI) source. The methodology applied was based on Youzbachi et al. (2015) with modification.
RESULTS AND DISCUSSION. Free fatty acids values ranged from 0.48 + 0.03 % to 1.07 + 0.00 %; consequently, all samples are in disagreement with the exposed in its respective labels, except the standard. Acidity in olive oil is the result of triacylglycerols breakdown, due to a chemical reaction called hydrolysis or lipolysis, in which free fatty acids are formed. Oil extracted carelessly and/or from poor quality fruits, fly infestation, delays between harvesting and extraction, damaged fruits, fungal diseases in fruit and prolonged contact between oil and vegetation water are factors leading to an elevated free fatty acid value. Storing olives in heaps or silos is also responsible for a high acidity. K 270 values ranged from 0.12 + 0.00 to 2.60 + 0.00, three olive oil samples presented values superior than established; 3, 6 and 7, besides SO. For K 232 values, all samples presented results within the required by legislation. For ΔK values, only 3, 6 and 7 obtained values above maximum limit, besides SO. The absorption at wavelength 232 nm is related to the formation of linoleic acid hydroperoxides, conjugated dienes and carboxylic compounds, while conjugated trienes absorbs at wavelength 270 nm. Moreover, K 232 value is reported as primary oil oxidation rate, whereas K 270 value is the secondary oxidation rate, plus in specific circumstances adulterated EVOO may present spectral characteristics analogous to refined oils. ΔK is based on the measurement of absorption intensity at 270 nm relative to conjugated trienes individual, discounting other chromophores influence that could be produced by olive oil oxidation. It is acknowledged that ΔK for EVOO oil is near zero, while for refined vegetable oils this value is superior to zero due to conjugated trienes formed during bleaching stage. A total of 17 fatty acids (FAs) were identified, though in two samples were encountered 23 fatty acids, five additional fatty acids are trans origin. Samples 3, 6 and 7 presented different fatty acid composition than the standard, being more similar to SO in relation to acid oleic and α-linoleic acids amounts. However, the study of fatty acid composition isolated is not sufficient to ensure the olive oil suitability once the adulteration could be in small percentages, consequently complementary analyzes are essential. Therefore, intending to create an innovative manner to investigate addition of SO oil in EVOO, the fingerprint of both oils was obtained. 22 TAGs were identified in both oils, but m/z 880-900 region demonstrates the occurrence of TAG encountered exclusively in SO; the cited region was expanded in order to confirm specifics TAG and a lipid marker for SO was defined: OLMo (m/z 886.68). Calibration curve of m/z 886.68 [TAG+NH4]+ was constructed taking into account its intensity versus SO percentage added to EVOO, achieving R = 0.9810 and y = 2.108 x + 109 obtained by linear regression. Thus, starting from line equation it is possible to determine the total of SO added to EVOO. Among all analyzed commercial samples, eight EVOO revealed some addition of SO, varying from 3.35 + 0.48 to 9.15 + 1.49 %.
CONCLUSIONS. The proposed method is fast; sixty seconds to obtain the mass spectrum of samples, conclusive; there is no requirement of endorsement with alternative methods, precise; low standard deviation and efficient; addition of 1% of SO could be detect in intentionally adulterated standard. Lastly, traditional low budget physico-chemical and chromatographic methods adopted by industry to endorse suitability of EVOO products are not effective, because it could just suggest possible crude fraud, but not confirm it as the proposed new method.
Keywords: direct infusion; mass spectrometry; extra virgin olive oil; soybean oil; fraud.

 Artigos Publicados Vinculados a Dissertação:

http://doi.org/10.1016/j.foodres.2017.09.076