2-hexenal--z-isomer and nonanal

Virgin olive oil is inevitably subject to an oxidation process during storage that can affect its stability and quality due to off-flavors that develop before the oil surpasses its 'best before' date. Many parameters are involved in the oxidation process at moderate conditions. Therefore, a multiparametric study is necessary to establish a link between physico-chemical changes and sensory quality degradation in a real storage experiment. In this context, a storage experiment of 27 months was performed for four monovarietal virgin olive oils, bottled in transparent 500-mL PET bottles and subjected to conditions close to a supermarket scenario. Volatile composition, quality parameters and phenolic compounds were determined monthly. Simultaneously, an accredited sensory panel assessed their sensory characteristics. The stability of the fresh samples was also studied with the oxidative stability index (OSI) and mesh cell-FTIR. (

Topics: Aldehydes; Food Storage; Olive Oil; Oxidation-Reduction; Phenols; Taste; Volatile Organic Compounds

Species of kalanchoe are rich in bioactive compounds and are widely used in folk medicine; however, these plants are not well known from the point of view of aroma. Two species, Kalanchoe pinnata and Kalanchoe daigremontiana, were examined after six months and two years of growth and their vitamin C content, succulence, and aroma composition were determined. The efficiency of juice extraction was highest (72%) for the leaves of K. daigremontiana after six months of growth. The concentration of vitamin C was highest in juices from two-year-old plants and much higher in the juice of K. pinnata (81 mg/100 g). SPME/GC/MS analysis identified 32 aroma components, considering those with the spectrum similarity over 75%. The main components were furan-2-ethyl, hexanal, 2-hexenal, 2,4-hexadienal, 1-octen-3-ol, nonanal. The quantitative relations of these compounds were somewhat different in the two species. The most dominant component, 2-hexenal, is responsible for the green-like aroma noted by the sensory panel.

Topics: Aldehydes; Alkadienes; Ascorbic Acid; Fruit and Vegetable Juices; Furans; Gas Chromatography-Mass Spectrometry; Kalanchoe; Octanols; Odorants; Plant Extracts; Plant Leaves; Principal Component Analysis

The interactions of soy protein isolate (SPI) and flavor compounds (hexanal, trans-2-hexenal, 1-octen-3-ol, trans-2-octenal, nonanal, and trans-2-nonenal) were investigated. The influence of SPI structure modified by malondialdehyde (MDA) and flavor compound structure on the interactions were determined by using headspace solid-phase microextraction (SPME) and gas chromatography (GC) combined with mass spectrometry (MS). The binding of native SPI to the flavor compounds decreased in the order trans-2-nonenal>nonanal>trans-2-octenal>trans-2-hexenal>hexanal>1-octen-3-ol. It might be attributed to that aldehydes are more hydrophobic than alcohols. The former is more conducive to hydrophobic binding with the SPI. Furthermore, the aldehydes, in particular trans-s-undecenal, could also react covalently. The effect of MDA modification on protein-flavor interactions depended on the structure of the flavor compound. Upon low concentration of MDA (≤1mM), the binding of all six flavors to SPI increased. However, a further increase in the extent of MDA (≥2.5mM), more soluble and even insoluble aggregates formed, which reduced the binding of hexanal and nonanal to SPI. The other four flavors with double bond revealed little changes in binding (trans-2-octenal, and trans-2-nonenal) or even an increase in binding (trans-2-hexenal, and 1-octen-3-ol). The results suggested that hydrophobic interactions were weakened upon high extent of oxidation, whereas covalent interactions were enhanced.

Topics: Alcohols; Aldehydes; Chromatography, Gas; Flavoring Agents; Hydrophobic and Hydrophilic Interactions; Malondialdehyde; Mass Spectrometry; Octanols; Odorants; Oxidation-Reduction; Particle Size; Solid Phase Microextraction; Soybean Proteins

The present study aimed to analyse the chemical components of the essential oil from Pyrrosia tonkinensis by GC-MS and evaluate the in vitro antibacterial activity. Twenty-eight compounds, representing 88.1% of the total essential oil, were identified and the major volatile components were trans-2-hexenal (22.1%), followed by nonanal (12.8%), limonene (9.6%), phytol (8.4%), 1-hexanol (3.8%), 2-furancarboxaldehyde (3.5%) and heptanal (3.1%). The antibacterial assays showed that the essential oil of P. tonkinensis had good antibacterial activities against all the tested microorganisms. This paper first reported the chemical composition and antimicrobial activity of the essential oil from P. tonkinensis.

Topics: Aldehydes; Anti-Bacterial Agents; Cyclohexenes; Gas Chromatography-Mass Spectrometry; Hexanols; Limonene; Microbial Sensitivity Tests; Oils, Volatile; Phytol; Plant Oils; Polypodiaceae; Terpenes