Utjecaj vrste na kakvoću komercijalnih fileta puževa

Research background. This study fulfils a need for investigation of a quality profile of snail fillets. Edible snails are a famous food product consumed worldwide and treated as delicacy. Nutritional value, colour and textural properties, such as hardness, are critical factors that impact consumer acceptance of the product. Hardness of snail meat is affected by its native original microstructure. Experimental approach. Fresh snails of the farmed species Cornu aspersum maximum, wild and farmed Cornu aspersum aspersum and wild Helix lucorum were used in order to investigate the qualitative profile of snail meat. Proximate composition, hardness and colour measurements were conducted on fillets of all species. The histological structure of the fillets of Cornu aspersum maximum was examined. Results and conclusions. Quality parameters of snail fillets were studied. A novel method of hardness analysis was proposed where the cylindrical part of snail fillets from the mid-posterior region with specific geometry 6 mm diameter and 6 mm height was used. The suitability of the mid-posterior region was enhanced by the uniform structure confirmed by the histological analysis. Helix lucorum snail fillet had the highest energy content and the highest hardness but the lowest carbohydrate content. The species Cornu aspersum maximum was evaluated with the highest values of a* (redness), b* (yellowness) and C* (chroma) compared to other species. Parameter L* (lightness) of wild snail fillets was lower than of the farmed ones due to age, diet, farming or environmental conditions, but it could also be related to snail carbohydrate content. Novelty and scientific contribution. This study yielded notable results on qualitative characteristics of snail fillets as food and important information is given on its meat properties. Furthermore, a novel methodology of hardness is provided in order to minimize natural, breeding and environmental influences. Finally, the research outcomes could lead to proper handling methods for further fabrication of snail meat.Pozadina istraživanja. Ovaj rad dopunjava istraživanje o kakvoći fileta puževa. Jestivi su puževi poznati prehrambeni proizvod širom svijeta i smatraju se delikatesom. Hranjiva vrijednost, boja i teksturalna svojstva, poput tvrdoće, bitni su čimbenici koji utječu na prihvatljivost proizvoda. Prirodna mikrostruktura utječe na čvrstoću mesa puževa. Eksperimentalni pristup. Za ispitivanje kakvoće mesa korišteni su svježi uzorci uzgojene vrste puža Cornu aspersum maximum, divlje i uzgojene vrste Cornu aspersum aspersum i divlje vrste Helix lucorum. Ispitani su kemijski sastav, tvrdoća i boja svih uzoraka puževa, te struktura tkiva fileta vrste Cornu aspersum maximum. Rezultati i zaključci. Ispitana je kakvoća fileta puževa i predložena nova metoda analize tvrdoće na cilindričnim uzorcima izrezanim iz sredine stražnjeg dijela fileta, promjera 6 mm i visine 6 mm. Histološka je analiza potvrdila da je taj dio fileta najprikladniji za analizu zbog svoje ujednačene strukture. Fileti vrste Helix lucorum imali su najveću energetsku vrijednost i tvrdoću, a najmanji udjel ugljikohidrata. Uzorci vrste Cornu aspersum maximum imali su najveće vrijednosti boje a* (crvena komponenta), b* (žuta komponenta) i C* (intenzitet obojenja). Vrijednost svjetloće L* uzoraka fileta divljih puževa bila je manja od one uzgojenih zbog starosti, prehrane te uvjeta uzgoja i okoliša, ali vjerojatno i zbog manjeg udjela ugljikohidrata. Novina i znanstveni doprinos. U ovom su radu izneseni važni rezultati ispitivanja kakvoće fileta puževa i dane bitne informacije o svojstvima mesa. Osim toga, prikazana je nova metoda analize tvrdoće, koja smanjuje utjecaj uzgoja i okoliša na rezultate ispitivanja. Rezultati istraživanja mogu pridonijeti pravilnom rukovanju pri uzgoju puževa

Proximate Composition, Predictive Analysis and Allometric Relationships, of the Edible Water Frog (Pelophylax epeiroticus) in Lake Pamvotida (Northwest Greece)

The edible water frog Pelophylax epeiroticus, distributed mainly in Northwest Greece and utilized commercially as food, was investigated in lake Pamvotida (Ioannina). The objective was to assess aspects of population structure (sex ratio, morphometric characteristics, allometric relationships) and proximate composition of the Epirus water frog (Pelophylax epeiroticus). Commercial samples (31 females and 54 males) were obtained and sex ratio, morphometric characteristics, allometric relationships and proximate composition were assessed. A significantly lower abundance of females was indicated (31 females and 54 males). Body length range was higher in females (females 3.4 mm, males 2.6 mm), whereas total weight range was higher in males (females 45.08 gr, males 48.35 gr). Differences in allometric relationships were indicated between sexes. The high protein (15.93 ± 3.32) and low lipid (0.25 ± 0.13) contents indicated that P. epeiroticus is an excellent food source of high nutritional value. A tree classification algorithm indicated that the principal contributing component for sex classification was dry matter, followed by a proportion of edible flesh and protein content. A predicted future increase in demand for wild-caught individuals requires the use of a suitable management plan, coupled with the development of farming practices aiming to assure the sustainable exploitation of this important resource and alleviate the pressure on its populations

Contribution to the study of the biology and ecology of pulmonate gastropods of lake Kerkini

Monthly and forthnightly samplings were taken between April 1989 and November 1991 for the study of biology and population dynamics of freshwater pulmonate gastropods in lake Kerkini. The study was carried out in the old river bed of Strymonas river, in the northern part of the lake, where three different pulmonate species coexisted, P. acuta, L. stagnalis and L. auricularia. The seasonal variation of the water temperature in the lake was the same throughout the three years of the study. Dissolved oxygen in the water, during 1991 ranged between 2 and 8 mg/ l reaching the lowest values in the summer and the highest in autumn. pH values ranged between 7.25 and 9.5 and conductivity between 250 and 480 μs/cm. . Total hardness values ranged between 80 and 250 mg CaCO3/ l , therefore water can be characterized as medium hard to hard. Variation was noted in the concentration of orthophosphate (from 0.01 to 0.10 mg/ l) and chloride (from 3 to 17.9 mg/ l) in the water during 1991, while the highest values in both cases appeared in summer and autumn. In the present study a quantitative sampler was used for plant and pulmonate samples from different depths. The abudance of the three pulmonate species was estimated in relation to the water volume at different water depths, as well as their horizontal and vertical distribution. Seasonal variation of the relative distribution by λ2 index showed that spatial distribution of all three species appeared contagious on water surface with the exception of early spring for L. stagnalis. For the later species more samples appeared with a random distribution in relation to water depth. The distribution of L. stagnalis and L. auricularia was contagious on the water surface but random in the deeper layers.Στο χρονικό διάστημα Aπρίλιος 1989 - Nοέμβριος 1991 πραγματοποιήθηκαν δεκαπενθήμερες και μηνιαίες δειγματοληψίες για τη μελέτη της βιολογίας και της δυναμικής των πληθυσμών των πνευμονοφόρων γαστεροπόδων της λίμνης Kερκίνης. H έρευνα έγινε στην παλιά κοίτη του ποταμού Στρυμώνα στο βόρειο τμήμα της λίμνης όπου συνυπήρχαν τρία είδη πνευμονοφόρων : η P. acuta η L. stagnalis και η L. auricularia. H εποχική διακύμανση της θερμοκρασίας του νερού της λίμνης ήταν όμοια και τα 3 χρόνια της μελέτης. Tο διαλυμένο στο νερό O2 στη διάρκεια του 1991 κυμάνθηκε από 2 έως 8 mg/ l με τις χαμηλότερες τιμές να εμφανίζονται το καλοκαίρι και τις υψηλότερες την άνοιξη και το φθινόπωρο. Tο pH κυμάνθηκε από 7.25 έως 9.5 και η αγωγιμότητα του νερού από 250 έως 480 μs/cm. Oι τιμές της ολικής σκληρότητας του νερού κυμάνθηκαν από 80 έως 250 mg CaCO3/ l και έτσι τα νερά χαρακτηρίστηκαν απο μετρίως σκληρά έως σκληρά. Στη διάρκεια του 1991 καταγράφηκε έντονη μεταβολή της περιεκτικότητας του νερού σε ορθοφωσφορικά (από 0.01 έως 0.10 mg/ l) και σε ιόντα χλωρίου (από 3 έως 17.9 mg/ l), ενώ οι υψηλότερες τιμές και στις δυο περιπτώσεις εμφανίστηκαν το καλοκαίρι. Στην παρούσα μελέτη χρησιμοποιήθηκε ποσοτικός δειγματολήπτης για λήψη δειγμάτων υδρόβιων φυτών και πνευμονοφόρων γαστεροπόδων παρέχοντας τη δυνατότητα για εκτίμηση της αφθονίας των σαλιγκαριών σε σχέση με τον όγκο του νερού και σε διαφορετικά βάθη αυτού. O έλεγχος ομοιογένειας των ποσοτικών δειγμάτων έδωσε πληροφορίες για την οριζόντια και κατακόρυφη κατανομή των τριών πνευμονοφόρων γαστεροπόδων στην παλιά κοίτη του Στρυμώνα

An Assessment of Snail-Farm Systems Based on Land Use and Farm Components

In this study, the structural and management characteristics of snail farms in Greece were analyzed to maximize sustainable food production. Objectives, such as the classification of farming systems and assessing the effects of various annual production parameters, were investigated. Data were collected (2017) via a questionnaire, and sampling was conducted in 29 snail farms dispersed in six different regions (Thrace, Central Macedonia, West Macedonia, Thessaly, Western Greece, and the Attica Islands). Descriptive statistics for continuous variables and frequencies for categorical variables were calculated. The similarity between farms was analyzed using nonmetric multidimensional scaling (nMDS). The average farm operation duration exceeded eight months and the mean annual production was 1597 kg of fresh, live snails. Results recorded five farming systems: elevated sections (7%), net-covered greenhouse (38%), a mixed system with a net-covered greenhouse (10%), open field (38%), and mixed system with an open field (7%). Snail farms differ in the type of substrate, available facilities, and equipment (60% similarity between most of the open field farms). The geographical location of a farms’ settlement affects productivity but also influences the duration of operation, especially in open field farms, due to their operation under a wide assortment of climatic types

Morphology and Genetic Structure Profile of Farmed Snails <i>Cornu aspersum aspersum</i> and <i>Cornu aspersum maximum</i> in Greece

The subspecies of the species Cornu aspersum, C. a. aspersum, and C. a. maximum are the dominant farmed species in Greece. The morphological and molecular polymorphism of the two aforementioned subspecies has not been studied in depth. In this study, the polymorphism of snails of the two subspecies derived from seven snail farms throughout Greece was studied using morphological and molecular markers. Firstly, the snail samples of both subspecies were categorized in three shell patterns based on shell color and existence of bands. The conducted population structure analysis revealed three major clusters among the farmed snail populations. As concerns genetic diversity, six loci (Ha5, Ha6, Ha8, Ha9, Ha10, and Ha11) were tested for their polymorphism. Genetic variation was reported within populations rather than among populations. Finally, the obtained data highlighted a common gene pool broodstock for snail farms throughout Greece

Different Interspecies Demographic Histories within the Same Locality: A Case Study of Sea Cucumbers, Cuttlefish and Clams in Greek Waters

Coalescent methods in population genetics aim to detect biodiversity patterns, evolutionary mechanisms, and signatures of historical changes in effective population sizes with respect to the species fidelity. Restriction site-associated DNA sequencing (RADseq) was used to evaluate the population dynamics of invertebrate species within the same localities. New sequencing technologies, such as the ones employed by population genetics, could be used to improve the management and sustainability of marine and aquaculture resources. Sea cucumbers (Holothuria tubolosa) showed genetic differentiation patterns favoring limited gene flow between studied areas. Similar results for clams (Venus verrucosa) suggest local adaptation and low-dispersal abilities for sessile organisms. On the contrary, cuttlefish (Sepia officinalis) exhibited a panmictic pattern, resulting in a single genetic stock in the area. The larvae settlement duration may be responsible for such interspecies variations. Interspecies demographic modeling revealed different environmental pressures of historical events’ signatures with respect to the three invertebrates. Sea cucumbers favor a post-glacial bottleneck event followed by a more recent recovery, whereas cuttlefish favor an expansion before the late glacial maximum. Lastly, clams showed a constant effective population size in the area. The results of historical demographic changes in natural populations provide opportunities for critical evaluation and management in terms of the conservation of the species in the area