Volatile Organic Compounds Profile in White Sturgeon (Acipenser transmontanus) Caviar at Different Stages of Ripening by Multiple Headspace Solid Phase Microextraction

Effects of the Species and Growth Stage on the Antioxidant and Antifungal Capacities, Polyphenol Contents, and Volatile Profiles of Bamboo Leaves

Bamboo leaves contain high concentrations of various biologically active compounds, such as polyphenols and volatiles, making them attractive as raw resources for antioxidant additives in the food industry. Here, we investigated the total phenolic content (TPC) and total flavonoid content (TFC) of four bamboo leaf extracts from two species (Phyllostachys edulis and Chimonocalamus delicatus) at two growth stages (first and second years). Antioxidant capacity was determined based on the radical-scavenging capacity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+). We also assessed the antifungal capacity based on mycelial growth inhibition of Colletotrichum musae (C. musae), Botrytis cinerea (B. cinereain), and Alternaria alternata (A. alternata). Pearson's correlation coefficients showed that the TPC was significantly (p < 0.01) negatively correlated with the half-maximal inhibitory concentrations against DPPH and ABTS+, whereas the TFC was positively correlated with C. musae and B. cinereain growth inhibition, which suggest that TPC and TFC might be the major contributors to the antioxidant and antifungal capacities of bamboo leaves, respectively. The volatile organic compounds (VOCs) of bamboo leaves were also analyzed using gas chromatography-ion mobility spectrometry. The VOCs included twenty-four aldehydes, eleven alcohols, four furans, seven esters, fifteen terpenes, three ketones, one pyrazine, and thirty unidentified compounds. Principal component analysis, partial least squares discriminant analysis, and hierarchical cluster analysis were performed to assess the differences in the volatile profiles of the four bamboo leaf samples, from which 23 discriminatory VOCs with variable importance in the projection values > 1 were screened, and part of them were impacted by species or growth stage. These findings provide a theoretical foundation for the use of bamboo leaves.

Correlation investigation between core microbe inoculation and the evolution of flavor characteristics during the storage of sturgeon caviar (Acipenser gueldenstaedtii)

The volatile and non-volatile compounds were monitored to investigate the microbial evolution associated with the characteristic flavors for sturgeon caviar during refrigeration. The results revealed that the composition of volatile compounds changed significantly with prolonged refrigeration time, especially hexanal, nonanal, phenylacetaldehyde, 3-methyl butyraldehyde, and 1-octen-3-ol. The nonvolatile metabolites were mainly represented by the increase of bitter amino acids (Thr. Ser, Gly, Ala, and Pro) and a decrease in polyunsaturated fatty acids, especially an 18.63 % decrease in 5 months of storage. A total of 332 differential metabolites were mainly involved in the biosynthetic metabolic pathways of α-linolenic acid, linoleic acid, and arachidonic acid. The precursors associated with flavor evolution were mainly phospholipids, including oleic, linoleic, arachidonic, eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids. The most abundant at the genus level was Serratia, followed by Arsenophnus, Rhodococcus, and Pseudomonas, as obtained by high-throughput sequencing. Furthermore, seven core microorganisms were isolated and characterized from refrigerated caviar. Among them, inoculation with Mammalian coccus and Bacillus chrysosporium restored the flavor profile of caviar and enhanced the content of nonvolatile precursors, contributing to the characteristic aroma attributes of sturgeon caviar. The study presents a theoretical basis for the exploitation of technologies for quality stabilization and control of sturgeon caviar during storage.

Effects of microbial diversity and phospholipids on flavor profile of caviar from hybrid sturgeon (Huso dauricus × Acipenser schrencki)

Thirty-seven volatiles were identified by gas chromatography-ion mobility spectrometry in sturgeon caviar. Alkenes (37, 43), alcohols (30, 36), aldehydes (9, 10), and esters (11, 13) were detected by two-dimensional gas chromatography-time-off-flight mass spectrometry in fresh and stored caviar, respectively. Alkenes (humulene, caryophyllene, longifolene, and d-limonene), aldehydes (heptanal, hexanal, pentanal, and 3-methyl butanal), and 2-ethyl-1-hexanol were sniffed and described as providing fresh, fatty, and fishy attributes by gas chromatography-olfactometry. The fungal genera of Apiotrichum, Penicillium, Filobasidium, Gibberella, and Cladosporium and 16 bacterial genera were significantly correlated with variations in the contents of 25 aldehydes and 11 ketones. Nine strains, 20 fatty acids, and 69 differential phospholipids were isolated and profiled. Glycerophosphoethanolamine (20:2/20:4), glycerophosphoethanolamine (22:6/22:5), and glycerophosphocholine (16:0/13:0) were significantly associated with the formation of odorants and the proposed mechanism of flavor formation from phospholipids is summarized. This study represents a foundation for achieving targeted preservation and flavor control of caviar.

Evolution of Food Safety Features and Volatile Profile in White Sturgeon Caviar Treated with Different Formulations of Salt and Preservatives during a Long-Term Storage Time

Caviar is a semi-preserved fish preparation in which cold storage (around 0 °C) and packaging under anaerobic conditions are fundamental to guarantee adequate safety parameters. Consumers seem to prefer caviar prepared with food salt only, but according to the needs of the different distribution channels, some preservatives are used in order to prolong its shelf life and to allow less restrictive storage conditions. Traditionally, the most common preservative was sodium tetraborate (borax), a salt that contributes to the sensory profile of caviar. However, due to its toxicity, borax has been banned in many countries, and the current trend is to reduce or eliminate its use. In this study, we evaluated the evolution of food safety parameters (pH, water activity, microbiological parameters) and the volatile profile during 14 months of storage in caviar samples treated with three different preservatives: I. exclusively NaCl, II. a mixture of borax and NaCl, and III. a mixture of organic acids and salts. Microbial presence was studied by means of plate counts; volatile organic compounds were identified on the sample headspace by means of solid phase microextraction with gas-chromatography and mass spectrometry. Results showed relevant differences among the three treatments investigated, with salt samples characterized by the highest viable counts and the greatest presence of volatile products driven by oxidative and spoilage processes, mainly occurring toward lipid and amino acids. On the contrary, the mixture of organic acids and salts showed the best response during the entire storage period. Finally, the employment of a multiparametric statistic model allowed the identification of different clusters based on the time of ripening and the preservative treatments used.

The Role of Lipid Composition in the Sensory Attributes and Acceptability of the Salted and Dried Mullet Roes (Bottarga): A Study in Human and Animal Models

A taste component is implicated in the oro-sensory detection of dietary lipids and free fatty acids seem to be involved in fatty food recognition. Bottarga, the salted and semi-dried ovary product of mullet (Mugil spp.), is a rich-fat food. A comparative sensory assessment of different commercial bottarga samples was performed in insect and human models in relation to their lipid composition. The bottarga attractant effect to Ceratitis capitata was assessed by behavioral tests. The subjective odor and taste perception of bottarga samples was investigated in human determining the rate of pleasantness, familiarity, and intensity dimensions using the 7-points Likert-type scale. Bottarga samples showed similar lipid profiles, but differences emerged in total and free fatty acid levels. Significant differences were observed in the attractant effect/acceptability of samples to medflies, negatively correlated to their total and free fatty acids. Insect female exhibited the ability to select among bottarga samples based on their visual and olfactory properties. In the human model, a potential contribution of free fatty acid amount in the pleasantness and familiarity dimensions of taste of bottarga samples was evidenced. Women exhibited a greater ability than men to select bottarga samples based on their better olfactory perception. Our results increase the knowledge about this outstanding product with nutritional and nutraceutical properties.