Plant materials that are used for the production of extruded meat analogs are often nutritionally incomplete and also contain antinutrients, thus there is a need to explore alternative plant proteins and pre-treatments. This study demonstrates application of phytase and fermentation to a pea-oat protein blend with a good essential amino acid profile and subsequent texturization using extrusion cooking. Enzymatic treatment reduced the content of antinutrient phytic acid by 32%. Extrusion also degraded phytic acid by up to 18%, but the effect depended on the material. Differences in physicochemical, sensorial, and textural properties between untreated and phytase-treated extruded meat analogs were small. In contrast, fermented material was more difficult to texturize due to degradation of macromolecules; physicochemical and textural properties of extrudates were markedly different; sensory analysis showed enhancement of flavor, but also detected an increase in some unwanted taste attributes (bitterness, cereal and off-taste). Phytic acid was not degraded by fermentation. Analysis of volatile compounds showed extrusion eliminated volatiles from the raw material but introduced Maillard reaction products. Overall, phytase treatment and fermentation demonstrated the potential for application in extruded meat analogs but also highlighted the necessity of optimization of process conditions.
The marine-derived fungus Stachylidium sp. was isolated from the sponge Callyspongia cf. C. flammea. Four new, putatively tyrosine-derived and O-prenylated natural products, stachylines A -D (1 -4), were obtained from the fungal extract. The structures of 1 -4 were elucidated based on extensive spectroscopic analyses. The absolute configuration of compound 2 was established by Mosher's method. Stachyline A (1) possesses a rare terminal oxime group and occurs as an interchangeable mixture of E/Z-isomers.The marine environment harbours approximately half of the global biodiversity and is estimated to contain between 3 and 500 million different species, offering an almost infinite resource for novel compounds. 1 Among these organisms marine-derived fungi became known as prolific producers of structurally most intriguing compounds. 2 In general, tyrosine derivatives have only rarely been reported from fungi, and in most cases such compounds were obtained from strains originating from environmentally extreme habitats, e.g. tyrosol carbamate which was isolated from the deep-water fungus Arthrinium sp. 3 Phytomyces sp., producing O-prenylated tyrosine derivatives, is an extremophile collected from an acid mine waste rich in toxic metals. 4 Another unusual case is aspergillusol A, an α-glucosidase inhibitor obtained from the sponge-derived fungus Aspergillus aculeatus which is reported to be the only known fungal tyrosine derivative to possess an oxime group. 5 Secondary metabolites with an oxime substituent are rare, and most of the reported examples have potent bioactivity, e.g. the actinomycete-derived nocardicins displayed strong antibiotic activity, 6 and brevioxime from Penicillium brevicompactum inhibited the biosynthesis of insect juvenile hormones. 7 P. olsonii produced 2-(4-hydroxyphenyl)-2-oxoacetaldehyde oxime (PHBA) which regenerated phosphorylated cholinesterase. 8 The oxime geometrical isomers collismycins A and B were isolated from Streptomyces sp. MQ22 which inhibited dexamethasone glucocorticoid receptor binding. 9During our search for new cytotoxic natural products an extract of the marine-derived fungus Stachylidium sp. was found to be active. During chromatographic separations it became clear that this fungus produces a vast array of secondary metabolites with intriguing structural features, among them the four novel, putatively tyrosine-derived and O-prenylated natural products, stachylines A -D (1 -4). Stachyline A (1) is distinguished by an oxime terminal group, probably derived through biosynthetic reactions similar to those known for cyanogenic glycosides and nocardicin A formation. [10][11][12][13][14] The molecules were evaluated in a number of biological assays, to date however no considerable activity was detected.* To whom correspondence should be addressed. Results and DiscussionThe RP-18 HPLC chromatogram of 1 contained two peaks (ratio 1:1), which when reinjected after their individual isolation, again resulted in the same chromatogram. This result suggested that compound 1 exi...
We applied capillary electrophoresis, liquid chromatography coupled with tandem mass-spectrometry (MS/MS), and ultra-performance liquid chromatography to determine the composition of water-insoluble and water-soluble proteinaceous fractions of the cheese and to study in detail the degradation of caseins during 8 mo of ripening of Estonian high-temperature cooked hard cheese Old Saare. The application of high-resolution and high-accuracy MS/MS enabled identification of more than 3,000 small peptides, representing a fairly full casein peptidome containing peptides of 4 to 25 AA in length: 1,049 from β-casein (CN), 944 from α-CN, 813 from α-CN, and 234 from κ-CN. The majority of β-CN- and α-CN-derived peptides originated from the N-terminal parts of the molecule, f6-93 and f1-124, respectively; peptides from α-CN arose predominantly from the C-terminal end f100-162. At the beginning of ripening, we found a relatively high amount of peptides originating from the glycomacropeptide part of κ-CN, whereas peptides from para-κ-CN prevailed during the later stages of ripening of the cheese. The cleavage patterns of β-CN, α-CN, as well as α-CN, showed that primary proteolysis was started mainly by plasmin, although a low proteolytic activity of chymosin was also evident. Based on the analysis of cleavage sites, we observed a significant participation of proteolytic enzymes, including amino- and carboxypeptidases, of both mesophilic and thermophilic starter bacteria in further hydrolysis of oligopeptides during the ripening. Several new phosphopeptides were detected in the result of MS/MS data analysis. The profiles of the estimated concentrations of phosphopeptides revealed that those originating from β-CN and α-CN accumulated during cheese maturation. In contrast, we did not notice any generation of phosphopeptides from the highly phosphorylated part of α-CN, f25-80, presumably due to the inaccessibility of this region to the action of plasmin and chymosin. The analysis of cleavage sites and the combination of principal component and clustering analyses provided a characterization of the complex dynamics of formation and degradation of peptides during cheese maturation. We made an attempt to obtain a comprehensive picture of proteolysis during Old Saare cheese ripening on the basis of the detailed peptidomic data, including also the less abundant peptides determined by MS/MS, and complemented by the data on intact caseins and free AA and reported the results in the paper.
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