Sanja Vidaček

Characterization of traditional Istrian dry-cured ham by means of physical and chemical analyses and volatile compounds

The aroma-active compounds of Istrian dry-cured ham were investigated by using headspace-solid phase microextraction and gas chromatography-mass spectrometry (GC-MS). Samples of biceps femoris were also evaluated by measuring physical and chemical characteristics: moisture, protein, fat, ash and NaCl content, a(w) value; colour: L*, a*, b* and oxidation of fat: TBARS test. About 50 volatile compounds were identified and quantified which belonged to several classes of chemical: 5 alcohols, 8 aldehydes, 7 alkanes, 1 ketone, 2 esters, 9 monoterpenes and 15 sesquiterpenes. Except volatile compounds derived from lipolysis and proteolysis the most abundant constituents were terpenes (62.97; 41.43%) that originate from spices added in the salting phase of the production process.

Determination of volatile compounds and quality parameters of traditional Istrian dry-cured ham.

The aim of this work was to determine the characteristics of Istrian dry-cured ham by instrumental methods and sensory analysis. The aroma-active compounds of Istrian dry-cured ham from 2010 and 2012 were investigated by using headspace-solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). Samples of biceps femoris were also evaluated by measuring physical and chemical characteristics. 92 volatile aroma compounds of Istrian dry-cured ham were found. Volatile compounds belonged to several chemical groups: aldehydes (51.4; 51.3%), terpenes (16.5; 16.4%), alcohols (15.5; 13.2%), ketones (8.6; 7.4%), alkanes (3.8; 5.7%), esters (1.3; 1.6%), aromatic hydrocarbons (0.8; 3.9%) and acids (0.6; 0.9%). Principal component analysis (PCA) showed that fat content, tenderness and melting texture were positively correlated. Terpenes were strongly correlated with flavour of added spices. Sweet taste and the presence of esters were positively correlated as well as negative odour, raw meat flavour and water content.

Determination of histamine in fish by Surface Enhanced Raman Spectroscopy using silver colloid SERS substrates

This study was focused on development of a rapid and sensitive method for histamine determination in fish based on Surface Enhanced Raman Spectroscopy (SERS) using simple and widely available silver colloid SERS substrate. Extraction of histamine with 0.4M perchloric acid and purification with 1-butanol significantly shortened sample preparation (30min) and provided clear SERS spectra with characteristic Raman bands of histamine. Principal component analysis effectively distinguished SERS spectra of fish samples with different histamine content. Partial least square (PLS) regression models confirmed reliability of detection and spectral analysis of histamine with SERS. In histamine concentration range 0-200mgkg-1, significant in legislative and fish quality control aspects, PLS regression model based on spectral range 1139.9-1643.7cm-1 showed linear trend with R2pred=0.962, RPD=7.250. Presented protocol for histamine extraction and purification followed by SERS analysis coupled with chemometric approach, enabled development of rapid and inexpensive method for histamine determination in fish.

Characterization of volatile compounds, physico-chemical and sensory characteristics of smoked dry-cured ham

Volatile compounds from smoked dry-cured ham were isolated by using headspace-solid phase microextraction and gas chromatography–mass spectrometry (GC–MS). Samples of biceps femoris were also evaluated for sensory physical and chemical characteristics. Eighty seven volatile aroma compounds of smoked dry-cured ham were identified. Chemical groups identified were aldehydes (35.6%), phenols (34.3%), alcohols (13.8%), terpenes (6.4%), aromatic hydrocarbons (2.6%), alkanes (2.2%), ketones (2.2%), esters (1.7%) and acids (0.7%). Except volatile compounds derived from lipolysis and proteolysis the second most abundant constituents were phenols that originate from smoking phase of the production process. The most abundant phenols were: 4-methylphenol, 3-methylphenol, 2-metoxy-4-methylphenol, 2-methylphenol, 2,6-dimethoxyphenol and 4-ethyl-2 methoxyphenol. Principal components analysis showed that NaCl and ash content positively correlated with the salty taste while fat content was correlated to marbling. Water content and aw value were negatively correlated with hardness of dry-cured ham while phenols were positively corelated with smoky aroma. Due to the different volatile composition and pronounced smoky aroma, smoked dry-cured ham can be distinguished from other types of dry-cured hams.

Salt and moisture content determination of fish by bioelectrical impedance and a needle-type multi-electrode array

ABSTRACT The aim of this study was to test the applicability of bioelectrical measurements and a needle-type multi-electrode array in evaluating salt and moisture content of structurally heterogeneous food samples, such as fish. Impedance measurements were performed at different frequencies in order to find the most appropriate range, where impedance module and/or phase angle are the most sensitive to salt and moisture content. The salt, moisture, and water phase salt (WPS) of the salted rainbow trout samples were successfully evaluated by the impedance module measured at 50 kHz (AdR2 > 0.85). Due to rapid and non-destructive analysis coupled with low cost device design, this method for determination of salt and/or moisture has potential as the quality control technique for the fish industry.

Safety of Fish Products

Abstract Traditional and ethnic foods have been the focus of many studies because they are widely consumed in developed and developing countries. However, information about food safety incidents linked to consumption of traditional and ethnic seafood is scarce. Traditional and ethnic seafood dishes do not seem to be of higher risk than other traditional or ethnic products. However, because seafood is linked to many food safety hazards, food safety principles should be implemented for the entire supply chain, which is especially important for the food service sector. When a traditional manufacturing process is altered in response to specific health trends or convenience, risk from biologic hazards may be elevated. If there is a lot of consumption of a particular traditional dish or product, exposure studies should be carried out to estimate the development of chemical hazards that may occur during processing.

A study of chemical profiles and appearance of white crystals in Istrian dry-cured ham: effect of desalting

Abstract In order to find out the effect on physical-chemical profile of Istrian dry-cured ham with particular regard to the appearance of white crystals in the muscles, raw salted legs were desalted by soaking the legs in cold water for 24 hours. The 20 raw hams taken from 10 slaughtered hogs (Swedish Landrace breed) and processed in the traditional Istrian manner were used. After salting and pressing, the raw hams were divided into two groups: 1) the 10 left legs of each hog were desalted (D); 2) the 10 right legs were not desalted (N). Following this, both groups of legs were subjected to continuous processing. Samples for chemical analysis and counting of white spots were taken from the 20 legs (10 N and 10 D) from 10 hogs, each weighing 12 to 15 kg. Chemical analysis of muscle tissue showed a highly significant difference (P<0.0001) in the salt quantity in the N (6.85%) and D (5.31%) dry-cured hams, as expected. Desalting affected the level of calcium which was higher (P=0.0124) in the D hams (0.27 g) than in the N hams (0.22 g). Desalting did not affect the free amino acid content, with the exception of methionine which was lower (P=0.0041) in D (0.14 g) than in N hams (0.17 g). Desalting affected the level of two free fatty acids as follows: heptadecanoic acid was higher (P=0.0203) in N (0.18%) than in D hams (0.24%) and DPA was higher (P=0.0373) in N (0.49%) than in D hams (0.39%). By counting the white precipitates, it was established that the regularity of appearance of the precipitate was noted on both the D and N hams, such that where there was no precipitate on the right N ham, nor was their any on the left D ham of the same hog. However, desalting only lead to a slight decrease in the appearance of precipitates (average of 0.7 points), but it is certain that desalting reduces the salt content in the legs, which affects some physical-chemical changes in the ham tissues during processing.

Hygienic Design of Fish Processing Equipment

Abstract Processing equipment which has been reported to be a source of pathogenic bacteria in the fish industry include conveyors, filleting machines, washing tanks, trimming tables, slicers, brining tanks, gutting machines including vacuum systems, and many others. Hygienic design of equipment is especially important for the fish industry because there are several aspects of fish processing that encourage bacterial spread and growth, of which the wet and humid environment is crucial. Some of the general hygienic design recommendations include open design, avoidance of hidden areas, hygienic sealing between different components, continuous removal of by-products, reduction of the number of different food contact surfaces, and drainability of equipment. Fish processing equipment has been much improved since 2000 in terms of the hygienic design, and nowadays the control of the environment is crucial.

NUTRITIVE VALUE OF TROUT (ONCORHYNCHUS MYKISS) FARMED IN ADRIATIC SEA

Cilj ovog rada bio je određivanje kemijskog sastava fileta svježe i hladno dimljene kalifornijske pastrve (Oncorhynchus mykiss) uzgojene u Jadranskom moru mjerenjem udjela vode, masti, proteina, soli, pepela, sastava masnih kiselina s naglaskom na eikozapentaensku (EPA) i dokozaheksaensku (DHA) masnu kiselinu te fizikalnih karakteristika mjerenjem pH i određivanjem boje. Analize su izvrsene na homogeniziranom misicju nakon odvajanja kože i kostiju. Određivanje udjela vode, pepela, ukupne kolicine masti i proteina izvrseno je prema referentnim metodama AOAC (1995). Za određivanje sastava masnih kiselina pripremljeni su metilni esteri prema metodi HRN EN ISO 5509 (2004) te su analizirani plinskom kromatografijom prema metodi HRN EN ISO 5508 (1999). Rezultati su pokazali da je istražena svježa pastrva uzgojena u moru odlican izvor proteina (21, 21%) te da ima nesto niže vrijednosti udjela masti (5, 21%) i omega-3 masnih kiselina (12, 52 %) od rezultata drugih istraživanja. Proces hladnog dimljenja ne uzrokuje gubitke na udjelu masti i omega-3 masnih kiselina. Fileti svježe i dimljene kalifornijske pastrve uzgojene u Jadranskom moru mogu se smatrati namirnicama visoke prehrambene vrijednosti.