Proton transfer reaction mass spectrometry: a green alternative for food volatilome profiling

Proton transfer reaction mass spectrometry (PTR-MS) has been developed for the direct, high sensitivity and high time resolution monitoring of volatile organic compounds (VOCs). Although PTR-MS development was not guided by greenness goals, most of its features perfectly fit within the green analytical chemistry (GAC) principles, making PTR-MS an intrinsically green analytical technique. Indeed, in its basic implementation, it does not require solvents or non-renewable carrier gases and, in principle, distilled water, used to feed the source where precursors ions are formed, is the only consumable. Food science and technology and agroindustry are amongst the fields where PTR-MS has been successfully exploited. Here we review and discuss, with emphasis on the GAC requirements, the potential of PTR-MS as a tool for both fundamental research and industrial applications in different food-related themes: i) food consumption and sensory, ii) bioprocess monitoring, iii) traceability, iv) quality control, and v) high-throughput food volatilome phenotyping. The outcome of all these related studies indicates PTR-MS both as a complementary tool to gas chromatographic methods and as a valuable technique when reduced analysis time, high sensitivity and/or on-line measurement are require

Effect of CO2 preservation treatments on the sensory quality of pomegranate juice

8openInternationalBothDue to the interest in identifying cost-effective techniques that can guarantee the microbiological, nutritional, and sensorial aspects of food products, this study investigates the effect of CO2 preservation treatment on the sensory quality of pomegranate juice at t0 and after a conservation period of four weeks at 4 °C (t28). The same initial batch of freshly squeezed non-treated (NT) juice was subjected to non-thermal preservation treatments with supercritical carbon dioxide (CO2), and with a combination of supercritical carbon dioxide and ultrasound (CO2-US). As control samples, two other juices were produced from the same NT batch: A juice stabilized with high pressure treatment (HPP) and a juice pasteurized at high temperature (HT), which represent an already established non-thermal preservation technique and the conventional thermal treatment. Projective mapping and check-all-that-apply methodologies were performed to determine the sensory qualitative differences between the juices. The volatile profile of the juices was characterized by gas chromatography-mass spectrometry. The results showed that juices treated with supercritical CO2 could be differentiated from NT, mainly by the perceived odor and volatile compound concentration, with a depletion of alcohols, esters, ketones, and terpenes and an increase in aldehydes. For example, in relation to the NT juice, limonene decreased by 95% and 90%, 1-hexanol decreased by 9% and 17%, and camphene decreased by 94% and 85% in the CO2 and CO2-US treated juices, respectively. Regarding perceived flavor, the CO2-treated juice was not clearly differentiated from NT. Changes in the volatile profile induced by storage at 4 °C led to perceivable differences in the odor quality of all juices, especially the juice treated with CO2-US, which underwent a significant depletion of all major volatile compounds during storage. The results suggest that the supercritical CO2 process conditions need to be optimized to minimize impacts on sensory quality and the volatile profile.openMosca, A.C.; Menghi, L.; Aprea, E.; Mazzucotelli, M.; Benedito, J.; Zambon, A.; Spilimbergo, S.; Gasperi, F.Mosca, A.C.; Menghi, L.; Aprea, E.; Mazzucotelli, M.; Benedito, J.; Zambon, A.; Spilimbergo, S.; Gasperi, F

High efficiency microfabricated planar columns for analysis of real-world samples of essential oils and plant volatile fraction

Compact and miniaturized instrumentation has obvious benefits in terms of energy consumption, materials, and laboratory space and, at the same time offers the possibility of “in-field” applications. In view of a possible application of on-chip GC for the analyses of essential oils in-situ with the industrial production and the volatile fraction emitted from plants, this study evaluates the performance of a set of planar columns developed to analyze complex mixtures. In a previous study, the performances of 2-m planar columns statically coated with apolar (Sil5%-PH), polar (FFAP-EXT), and chiral (Et-β-CD) stationary phases were tested. The results were comparable to those of reference conventional NB columns, efficiency achieving a number of theoretical plates per meter (N/m) ranging from 5700 for Et-β-CD to 7200 for Sil5%-PH [1]. Plant and food volatile fractions are characterized by high complexity and usually consist of components within a widely extended range of volatility and polarity. A reliable chemical analysis, therefore, requires columns with a high separation power. One of the ways to deal with this issue successfully is to increase column length while keeping high efficiency and selectivity. A set of 5-m planar columns (60 x 80 µm; nominal dc 0.71 µm) coated with the same stationary phases as in the previous study was therefore developed. Column performances were tested by analyzing essential oils (peppermint, lavender, chamomile, rosemary, tea tree, and bergamot) and headspace of the same aromatic plants, as well as standard mixtures of related compounds. The results were compared to those obtained with the 2-m planar columns of the previous study taken as reference. The 5-m planar columns provide separations of the components of the investigated samples fully overlapping on the corresponding conventional NB column. Their chromatographic performances were highly satisfactory achieving efficiency higher than the previous ones with N/m reaching 9300 for the FFAP-EXT planar column, and significantly increasing the retention of highly volatile compounds, thereby providing a drastic increase of their separation power (i.e. peak capacity). These results show that 5-m planar columns can provide performances that make them able to satisfy all requirements for a reliable analysis of complex samples such as essential oils and plant volatile fractions

Over-expression of a tomato N-acetyl-L-glutamate synthase gene (SlNAGS1) in Arabidopsis thaliana results in high ornithine levels and increased tolerance in salt and drought stresses

A single copy of the N-acetyl-L-glutamate synthase gene (SlNAGS1) has been isolated from tomato. The deduced amino acid sequence consists of 604 amino acids and shows a high level of similarity to the predicted Arabidopsis NAGS1 and NAGS2 proteins. Furthermore, the N-terminus ArgB domain and the C-terminus ArgA domain found in SlNAGS1 are similar to the structural arrangements that have been reported for other predicted NAGS proteins. SlNAGS1 was expressed at high levels in all aerial organs, and at basic levels in seeds, whereas it was not detected at all in roots. SlNAGS1 transcript accumulation was noticed transiently in tomato fruit at the red-fruit stage. In addition, an increase of SlNAGS1 transcripts was detected in mature green tomato fruit within the first hour of exposure to low oxygen concentrations. Transgenic Arabidopsis plants have been generated expressing the SlNAGS1 gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter. Three homozygous transgenic lines expressing the transgene (lines 1-7, 3-8, and 6-5) were evaluated further. All three transgenic lines showed a significant accumulation of ornithine in the leaves with line 3-8 exhibiting the highest concentration. The same lines demonstrated higher germination ability compared to wild-type (WT) plants when subjected to 250 mM NaCl. Similarly, mature plants of all three transgenic lines displayed a higher tolerance to salt and drought stress compared to WT plants. Under most experimental conditions, transgenic line 3-8 performed best, while the responses obtained from lines 1-7 and 6-5 depended on the applied stimulus. To our knowledge, this is the first plant NAGS gene to be isolated, characterized, and genetically modified

Differential regulation of alanine aminotransferase homologues by abiotic stresses in wheat (Triticum aestivum L.) seedlings

Wheat (Triticum aestivum L.) seedlings contain four alanine aminotransferase (AlaAT) homologues. Two of them encode AlaAT enzymes, whereas two homologues act as glumate:glyoxylate aminotransferase (GGAT). To address the function of the distinct AlaAT homologues a comparative examination of the changes in transcript level together with the enzyme activity and alanine and glutamate content in wheat seedlings subjected to low oxygen availability, nitrogen and light deficiency has been studied. Shoots of wheat seedlings were more tolerant to hypoxia than the roots as judging on the basis of enzyme activity and transcript level. Hypoxia induced AlaAT1 earlier in roots than in shoots, while AlaAT2 and GGAT were unaffected. The increase in AlaAT activity lagged behind the increase in alanine content. Nitrogen deficiency has little effect on the activity of GGAT. In contrast, lower activity of AlaAT and the level of mRNA for AlaAT1 and AlaAT2 in wheat seedlings growing on a nitrogen-free medium seems to indicate that AlaAT is regulated by the availability of nitrogen. Both AlaAT and GGAT activities were present in etiolated wheat seedlings but their activity was half of that observed in light-grown seedlings. Exposure of etiolated seedlings to light caused an increase in enzyme activities and up-regulated GGAT1. It is proposed that hypoxia-induced AlaAT1 and light-induced peroxisomal GGAT1 appears to be crucial for the regulation of energy availability in plants grown under unfavourable environmental conditions

Coping with Fungal Diseases in Crops: New Advances in Genomics, Breeding and Management

This Special Issue comprises a collection of eight peer-reviewed articles centered around the plant–pathogen interaction with the aim of proposing strategies that enhance plant resistance to pathogens and limit the damage to crop production, utilizing a multidisciplinary approach [...