Effect of Ultra-High Pressure Homogenization (UHPH) and Conventional Thermal Pasteurization on the Volatile Composition of Tiger Nut Beverage

Tiger nut beverages are non-alcoholic products that are characterized by their pale color and soft flavor. Conventional heat treatments are widely used in the food industry, although heated products are often damaging to their overall quality. Ultra-high pressure homogenization UHPH) is an emerging technology that extends the shelf-life of foods while maintaining most of their fresh characteristics. The present work deals with the comparison of the effect of conventional thermal homogenization-pasteurization (H-P, 18 + 4 MPa at 65 °C, 80 °C for 15 s.) and UHPH (at 200 and 300 MPa, and inlet temperature of 40 °C), on the volatile composition of tiger nut beverage. Headspace-solid phase microextraction (HS-SPME) was used for detecting volatile compounds of beverages, which were then identified by gas chromatography-mass spectrometry (GC-MS). A total of 37 different volatile substances were identified in tiger nut beverages, which were primarily grouped into the aromatic hydrocarbons, alcohols, aldehydes and terpenes chemical families. Stabilizing treatments increased the total amount of volatile compounds (H-P > UHPH > R-P). H-P was the treatment that produced the most changes in the volatile composition of RP, while treatment at 200 MPa had a minor impact. At the end of their storage, these products were also characterized by the same chemical families. This study evidenced the UHPH technology as an alternative processing of tiger nut beverages production that minimally modifies their volatile composition.

Volatile Composition Variability of Arnica montana Wild Populations of Trentino-Alto Adige, Italy, Determined by Headspace-Solid Phase Microextraction

Arnica montana is a plant distributed in most of Europe, including the Alpine arc and Apennines in Italy, and traditionally used worldwide for medicinal properties. Twelve natural populations of the species from Trentino-Alto Adige, Italy, were characterized using Headspace-Solid Phase Microextraction analysis for their volatile profile. Fifty-one compounds were detected in flower heads, the most abundant being (E)-Caryophyllene (23.4 %), 2,2,4,6,6-Pentamethylheptane (8.3 %), α- trans-Bergamotene (7.2 %), Germacrene D (5.7 %), and Hexanal (5.3 %). A multivariate analysis performed on the ten most abundant compounds grouped these investigated accessions into five main clusters. Three clusters, comprising together five accessions, were linked to the geographical origin of two collection sites. This work is a complete characterization of volatiles of the species by SPME analysis reported to date. Furthermore, results suggest that the species' volatile profile can be linked to the geographical origin of the natural populations and, therefore, represent a tool for evaluating biodiversity within the species.

Optimization of Headspace Solid-Phase Microextraction (HS-SPME) Parameters for the Analysis of Pyrazines in Yeast Extract via Gas Chromatography Mass Spectrometry (GC-MS)

Yeast extract was analyzed through headspace solid-phase microextraction (HS-SPME) in combination with (GC-MS) for its pyrazine compounds. Four different types of SPME fibers with various polarities were selected for preoptimization. The three coated fiber 50/30 µm DVB/CAR/PDMS showed the maximum volatile extraction efficiency and was selected for further analysis. Twenty-eight volatile compounds were tentatively identified through GC-MS including eight pyrazines and were categorically characterized as major volatile compounds responsible for the flavor enhancing notes in YE. Response surface methodology encoded with face centered central composite design was employed to optimize the experimental design. Average peak area of selected pyrazines; methylpyrazine, 2,3-dimethylpyrazine, 2,6-dimethylpyrazine, 2-ethyl-5-methylpyrazine, trimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, tetramethylpyrazine, 3,5-diethyl-2-methylpyrazine, and 2,3,5-trimethyl-6-ethylpyrazine were optimized through RSM-CCD to get the best conditions for HS-SPME. The HS-SPME variables X₁ (equilibrium time), X₂ (extraction time), and X₃ (extraction temperature) were programed into the run sheets to opt an optimistic statistical approach. Among these, the variable X₂ and X₃ showed the most significant results with the response variable R and could be concluded as the most tantalize variables while practicing pyrazines extraction through HS-SPME method. Resultantly, the optimization methodology was successfully applied for the extraction of pyrazines from yeast extract. PRACTICAL APPLICATION: The selection of optimal conditions to conduct a HS-SPME experiment can dramatically affect the sensitivity and accuracy of aroma extraction process. Optimizing the SPME conditions is the best way to identify the role of all the possible factors that can fluctuate the volatile profile of any sample. This type of statistical approach to optimize the HS-SPME conditions for pyrazines in yeast extract was practiced for the very first time and could be considered as a prerequisite strategy to proliferate future projects related to some novel studies in terms of pyrazines flavor perception.

GC-MS study of changes in polar/mid-polar and volatile compounds in Persian lime (Citrus latifolia) during fruit growth

BACKGROUND

Citrus fruits possess a high content of bioactive compounds whose changes during fruit maturation have not been studied in depth. Fruits were sampled from week 1, after fruit onset (7 days after flowering), to week 14. Volatile compounds isolated by headspace-solid-phase microextraction and polar extracts from all samples were analyzed by gas chromatography-mass spectrometry.

RESULTS

The relative abundance of 107 identified metabolites allowed differences among samples at different stages of fruit growth to be established. Principal component analysis showed a clear discrimination among samples, and analysis of variance revealed significant differences in 94 out of the 107 metabolites. Among total volatiles, monoterpenes increased their relative abundance from 86% to 94% during fruit growth, d-limonene, γ-terpinene and β-pinene being the most abundant; conversely, sesquiterpenes decreased from 11.5% to 2.8%, β-bisabolene and α-bergamotene being the most concentrated. Sugars, in general, exhibited a gradual increase in abundance, reaching a maximum between weeks 9 and 12. Citric and malic acids, representing approximately 90% of the total identified carboxylic acids, reached a maximum concentration at commercial maturity (week 14).

CONCLUSION

Of the 107 tentatively identified metabolites during Persian lime growth, sugars, carboxylic acids, and volatiles were those that experienced more significant changes and more clearly created differences among fruit growth stages. © 2018 Society of Chemical Industry.