Ricardo Malheiro

Influence of spike lavender (Lavandula latifolia Med.) essential oil in the quality, stability and composition of soybean oil during microwave heating.

Lipids oxidation is one of the main factors leading to quality losses in foods. Its prevention or delay could be obtained by the addition of antioxidants. In this sense the present work intend to monitor the protective effects of Lavandula latifolia essential oil during soybean oil microwave heating. To achieve the proposed goal quality parameters (free acidity, peroxide value, specific coefficients of extinction and ΔK), fatty acids profile, tocopherols and tocotrienols composition, antioxidant activity and oxidative stability were evaluated in soybean oil with and without spike lavender essential oils (EO) submitted to different microwave heating exposure times (1, 3, 5, 10 and 15 min; 1000 Watt) with a standard domestic microwave equipment. Microwave heating induced severe quality and composition losses, mainly above 3 min of microwave heating, regardless the sample tested. However, spike lavender EO addition counteracts the oxidation comparatively to control oils, by presenting enhanced values in quality parameters. A higher protection in unsaturated fatty acids loss was also observed as well as a higher antioxidant activity and oxidative stability. The microwave heating effects were clearly different in the samples with essential oils addition, allowing discrimination from plain soybean oils by a principal component analysis, being also capable to discriminate the different heating times tested within each sample.

Effect of Olive Leaves Addition during the Extraction Process of Overmature Fruits on Olive Oil Quality

The harvest period is one of the most important factors influencing olive oil quality. This period is extended for several months and the late-extracted olive oils are characterized by quality loss and reduced resistance to oxidation. The aim of this work was to verify the effect of olive leaves addition during the oil extraction process in the olive oils quality and composition. In two consecutive years (2009 and 2010), different olive leaves amounts (1%, 2.5%, 5% and 10% w/w) were added during the extraction process of cv. Cobrançosa olive fruits, collected in the late season. Standard quality parameters, oxidative stability, fatty acids profile, tocopherols, chlorophylls, and carotenoids contents were evaluated. Olive leaves addition induces a slight increase in acidity, peroxide value, K232, and K270 without compromising olive oils classification, but the resistance to oxidation was significantly improved. Vitamin E increased nearly 30% with 10% of leaves added mainly due to the considerable increase in α-tocopherol. A similar effect was observed in the contents of chlorophylls (chlorophyll a and pheophytin a) and carotenoids (lutein and β-carotene), that attributed a more intense greener pigmentation and enhanced nutritional attributes. Significant correlations were observed for several parameters with the amounts of leaves added. Moreover, leaves addition modified the characteristics and composition of the olive oils in a way that was possible to discriminate and to classify each group.

Determination of the volatile profile of stoned table olives from different varieties by using HS-SPME and GC/IT-MS

BACKGROUND The volatile composition of alcaparras stoned table olives produced from five of the most representative olive cultivars (cv. Cobrançosa, Madural, Negrinha de Freixo, Santulhana and Verdeal Transmontana) from the Trás-os-Montes region (north-east of Portugal) was analytically characterised using headspace-solid phase microextraction/gas chromatography-ion trap-mass spectrometry. RESULTS Overall, 42 volatile compounds were identified, belonging to distinct chemical classes: 15 aldehydes, seven esters, five alcohols, five sesquiterpenes, four norisoprenoids derivates, three monoterpenes, o ne ketone and two alkenes. Aldehydes were the major chemical class identified in all olive cultivars studied (more than 74% of all the volatile compounds identified). Hexanal, phenylacetaldehyde and (E,E)-2,4-heptadienal were the major volatile compounds identified. CONCLUSIONS It was possible to discriminate the results obtained from the volatile profile of the five olive cultivars by using principal component analysis. Both qualitative and quantitative fractions of alcaparras table olives were influenced by olive cultivar, which confers a single aroma. This fact certainly influences consumer preference and acceptability towards a specific olive cultivar.

Olive Volatiles from Portuguese Cultivars Cobrançosa, Madural and Verdeal Transmontana: Role in Oviposition Preference of Bactrocera oleae (Rossi) (Diptera: Tephritidae).

The olive fly, Bactrocera oleae (Rossi), a serious threat to the olive crop worldwide, displays ovipositon preference for some olive cultivars but the causes are still unclear. In the present work, three Portuguese olive cultivars with different susceptibilities to olive fly (Cobrançosa, Madural, and Verdeal Transmontana) were studied, aiming to determine if the olive volatiles are implicated in this interaction. Olive volatiles were assessed by SPME-GC-MS in the three cultivars during maturation process to observe possible correlations with olive fly infestation levels. Overall, 34 volatiles were identified in the olives, from 7 chemical classes (alcohols, aldehydes, aromatic hydrocarbons, esters, ketones, sesquiterpenes, and terpenes). Generally, total volatile amounts decrease during maturation but toluene, the main compound, increased in all cultivars, particularly in those with higher susceptibility to olive fly. Sesquiterpenes also raised, mainly α-copaene. Toluene and α-copaene, recognized oviposition promoters to olive fly, were correlated with the infestation level of cvs. Madural and Verdeal Trasnmontana (intermediate and highly susceptible cultivars respectively), while no correlations were established with cv. Cobrançosa (less susceptible). No volatiles with inverse correlation were observed. Volatile composition of olives may be a decisive factor in the olive fly choice to oviposit and this could be the basis for the development of new control strategies for this pest.

Improvement of stability and carotenoids fraction of virgin olive oils by addition of microalgae Scenedesmus almeriensis extracts.

Humans are not capable of synthesizing carotenoids de novo and thus, their presence in human tissues is entirely of dietary origin. Consumption of essential carotenoids is reduced due to the lower intake of fruits and vegetables. Microalgae are a good source of carotenoids that can be exploited. In the present work, carotenoids rich extracts from Scenedesmus almeriensis were added to extra-virgin olive oils at different concentrations (0.1 and 0.21 mg/mL) in order to enhance the consumption of these bioactives. Extracts brought changes in olive oils color, turning them orange-reddish. Quality of olive oils was improved, since peroxidation was inhibited. Olive oils fatty acids and tocopherols were not affected. β-carotene and lutein contents increase considerably, as well as oxidative stability, improving olive oils shelf-life and nutritional value. Inclusion of S. almeriensis extracts is a good strategy to improve and enhance the consumption of carotenoids, since olive oil consumption is increasing.

Chemical characterization of "alcaparras" stoned table olives from northeast Portugal.

Commercial stoned table olives named “alcaparras” from Trás-os-Montes (Portugal) were chemically characterized. During three consecutive years (2004–2006) 30 samples (10 per year) were examined for their nutritional value (moisture, crude protein, total fat, ash, carbohydrates, and energy), with a detailed report of the fatty acids and tocopherols composition. Water was the major constituent (72.5 ± 5.5%), followed by fat (14.6 ± 5.1%). The average amount of protein and ash were 1.1% and 3.4%, respectively, reporting unusual ash values for table olives, related to the technological process. One hundred grams of fresh stoned table olives presented an average energetic value of 156 kcal, lower than most table olives. The lipids are rich in oleic acid (average of 77.7 ± 2.0%), followed by palmitic acid and linoleic acid. Samples showed an average of total tocopherols of 1.2 mg/100 g of fresh weight, being α-tocopherol the most abundant. Table olives are important sources of MUFA, as olive oil, recognized as a preventive factor in diseases in which free radicals are implicated, complemented by the amounts of vitamin E, with both antioxidant and vitamin action.

Microwave Heating: A Time Saving Technology or a Way to Induce Vegetable Oils Oxidation?

The use of microwave radiation for food heating was discovered unintentionally in 1945 by Dr. Percy Spencer (Osepchuk, 1984). In the following years several experiments were conducted in order to improve the technology and food application fields, being exclusively used at the industrial level, mostly for drying, baking, and thawing. The popularization of domestic microwave ovens started in the 70’s (Osepchuk, 1984) once the improvements allowed price and size reduction. Microwaves are now indispensible equipments in westerns modern kitchens. Although there is no formal definition of the frequency range for microwave radiation, these electromagnetic waves occur in the 300MHz 300GHz region. Nevertheless, and in accordance with the industrial, scientific and medical (ISM) frequency bands for noncommunication purposes, only 915 MHz and 2.45GHz are used for food applications, especially the second due to its worldwide availability. In domestic equipments, these microwaves (high frequency oscillating electric and magnetic fields) are produced inside the oven, when electrons resonate at high frequencies in an electron tube called magnetron. The electric field is created through an inner cathode and an outer anode presenting a large potential difference between both. Permanent magnets, which compose the magnetron, are responsible for the magnetic field. Once heated, the cathode releases the electrons, traveling from the cathode in an outward spiraling path, eventually making their way to the anode. As the electrons go by resonance chambers, energy is released and received as microwaves by the output antenna. The microwaves are applied to the cavity oven, where the food is heated, via waveguides (Mutyala et al., 2010). The microwaves are reflected and distributed by the stirrer fan and then reflected again by the metallic walls of the container, being absorbed by food and lead to its temperature rise (Fig. 1). This capability to absorb microwave energy is governed by food dielectric properties, and involves primarily two mechanisms: dipolar relaxation and ionic conduction. Food water is often the primary component responsible for dielectric heating. Because of its dipolar nature, water molecules tend to re-orientate with the high frequencies

Identification of leaf volatiles from olive (Olea europaea) and their possible role in the ovipositional preferences of olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae)

The olive fly, Bactrocera oleae (Rossi), is a monophagous pest that displays an oviposition preference among cultivars of olive (Olea europaea L.). To clarify the oviposition preference, the olive leaf volatiles of three olive cultivars (Cobrançosa, Madural and Verdeal Transmontana) were assessed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) at six different periods of olive fruit maturation and degrees of infestation. A total of 39 volatiles were identified, mainly esters and alcohols, with a minor percentage of aldehydes, ketones and terpenic compounds, including sesquiterpenes. At sampling dates with higher degrees of infestation, cv. Cobrançosa had, simultaneously, significantly lower infestation degrees and higher volatile amounts than the other two cultivars, with a probable deterrent effect for oviposition. The green leaf volatiles (GLVs) (Z)-3-hexen-1-ol and (Z)-3-hexen-1-ol acetate) were the main compounds identified in all cultivars, together with toluene. The abundance of GLVs decreased significantly throughout maturation, without significant differences among cultivars, while toluene showed a general increase and positive correlation with olive fly infestation levels. The results obtained could broaden our understanding of the roles of various types and amounts of olive volatiles in the environment, especially in olive fly host selection and cultivar preference.