Solid-phase microextraction (SPME) is a simple, sensitive, rapid and solvent-free technique for the extraction of analytes from gaseous, liquid and solid samples and takes a leading position among microextraction methods. Application of SPME in sample preparation has been increasing continuously over the last decade. It is most often used as an automatized fiber injection system coupled to chromatographic separation modules for the extraction of volatile and semivolatile organic compounds and also allows for the trace analysis of compounds in complex matrices. Since SPME was first introduced in the early 1990s, several modifications have been made to adapt the procedure to specific application requirements. More robust fiber assemblies and coatings with higher extraction efficiencies, selectivity and stability have been commercialized. Automation and on-line coupling to analytical instruments have been achieved in many applications and new derivatization strategies as well as improved calibration procedures have been developed to overcome existing limitations regarding quantitation. Furthermore, devices using tubes, needles or tips for extraction instead of a fiber have been designed. In the field of food analysis, SPME has been most often applied to fruit/vegetables, fats/oils, wine, meat products, dairy and OPEN ACCESS Chromatography 2015, 2 294 beverages whereas environmental applications focus on the analysis of air, water, soil and sediment samples.

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In Germany, the best‐selling fish products are canned and marinated fish products including deep‐fried and pickled herring products. During processing, pre‐salted herring fillets are breaded, deep‐fried, and covered by an aqueous marinade containing vinegar and sodium chloride. For shelf‐life extension, the packaged fish can be pasteurized. Due to the co‐occurrence of sodium chloride and glycerol derivatives such as tri‐ or diacylglycerides, the deep‐frying and pasteurization procedure may lead to the formation of fatty acid esters of 2‐monochloropropane‐1,3‐diol and 3‐monochloropropane‐1,2‐diol (MCPD‐E) and of glycidol (G‐E). Various product as well as process dependent parameters on the formation of MCPD‐E and G‐E in deep‐fried and pickled herring products are studied. The frying‐life of the oil has the strongest effect on the formation of MCPD‐E in herring products. 3‐MCPD‐E contents increases from 341 ± 48 to 1133 ± 194 μg kg−1 lipid in the products after 9 days frying‐life of the oil. Moreover, it is shown that the major proportion of MCPD‐E in these products originates from the deep‐frying oil. The analyses of total polar material and spectrophotometric measurement of the absorption at 420 nm of the deep‐frying oil are identified as suitable screening methods for estimating MCPD‐E contents in deep‐fried and pickled herring products. Practical Applications: Canned and marinated fish products are the best‐selling fish products (28% market share) on the German market. Up to now, no studies regarding the deep‐frying procedure of pickled herring products are published. Deep‐frying has shown to be a process leading to MCPD‐E and G‐E in fish products mainly affected by intake of deep‐frying oil. The knowledge about the effect of process and product based parameters on the formation of MCPD‐E and G‐E in deep‐fried and pickled herring products may be of particular interest for the fish‐processing industry in order to manage that quality issue. Moreover, methods for the assessment of the deep‐frying oil quality such as the analysis of the total polar material (TPM) and the spectrophotometric measurement of the absorption at 420 nm deemed suitable screening methods for estimating the MCPD‐E contents in deep‐fried and pickled herring products. Deep‐frying of pickled herring products leads to the formation of MCPD‐E and G‐E, mainly affected by intake of deep‐frying oil and the frying‐life of the oil. Methods for the assessment of the frying oil quality, such as the analysis of TPM and the spectrophotometric measurement of the absorption, are suitable screening methods for estimating the MCPD‐E contents in deep‐fried fish products.

In the present study, existing official methods for oils were modified in order to analyze free and bound MCPD and bound glycidol in fish. Free 3-MCPD was determined in aqueous extracts of fishery products. DGF standard methods C-VI-17(10) and C-VI-18(10) and the 3 in 1 method were modified and tested to quantify ester-bound 2-and 3-MCPD and glycidyl esters. The different methods were validated using spiked fish mince and a naturally contaminated reference material consisting of homogenized smoked sprat and fish sticks. The methods showed good agreement. Assay B of the modified DGF method C-VI-18(10) and the adapted 3 in 1 method allow a quantitative determination of bound 2-and 3-MCPD in fishery products. In addition, glycidyl esters can be quantified applying the 3 in 1 method. The screening of various fishery products showed that smoked fish may contain considerable amounts of free 3-MCPD. Concentrations ranged between 8 and 388 mg/kg wet weight (ww). Only traces of free 3-MCPD were found in all other fishery products. Fish sticks and fried fish products are potential sources of 3-and 2-MCPD esters, but large variation were observed. Bound 3-MCPD ranged between 45 and 377 mg/kg ww, bound 2-MCPD between 9 and 116 mg/kg ww. Practical applications:The European Food Safety Authority (EFSA) is calling for occurrence data of 2-MCPD, 3-MCPD, 2-MCPD ester, 3-MCPD ester, and glycidyl ester in foods including fishery products. At present, there is no official method for the determination of these food processing contaminants in fish and fishery products. Therefore, the approach of this study was to establish analytical methods for the quantification of free and bound MCPD and bound glycidol in fish, based on the modification of existing methods for edible oils. The adapted methods allow a sensitive quantitative determination of the target analytes in various fishery products.

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To provide a comprehensive overview of the amounts of unesterified and bound 2- and 3-monochloropropanediol (MCPD) and glycidyl esters (G–E) in processed fishery products sold in Germany, an analysis of various frequently consumed products was conducted. In total, 258 commercial samples of breaded and pre-fried fishery products (e.g., frozen fish fingers), fried fish products (e.g., products in marinade), canned fish, smoked fish and some smoked spice preparations were examined. In addition, the effect of different kitchen preparation methods (e.g., baking, frying and roasting) on the MCPD and G–E amounts of fish fingers was studied. The mentioned process contaminants, MCPD and G-E, were quantifiable in the majority of the samples. Although pre-fried and fried fishery products predominantly contained MCPD esters (MCPD-E), mainly free MCPD was found in smoked fish. Compared with other types of smoke generation, hot smoked fish prepared in traditional Altona smoking kilns contained, on average, the highest 3-MCPD contents (range: 12–246 µg/kg). The amounts of bound MCPD in the fried fish products (range for 3-MCPD-E: < LOQ-808 µg/kg) were not significantly different from the amounts in the investigated pre-fried fish samples (range for 3-MCPD-E: < LOQ-792 µg/kg). However, they differ significantly from the amounts in unfried products (< LOQ). After preparation in the kitchen, the contents in the ready-to-eat fish fingers depend primarily on the initial contaminant amounts of the frozen product and/or the frying oil, respectively.

Trans fatty acids (TFA) are considered undesirable food components due to their unequivocally proven negative effects on cardiovascular health. Twelve virtually TFA free deep‐frying fats were developed by blending various liquid and solid vegetable fat components and characterized in terms of their technofunctional‐sensory properties. The aim was to develop fat blends with similar or improved technofunctional‐sensory properties as common deep‐frying fats for bakery applications. For this purpose, foaming and splattering behavior during deep‐frying, melting behavior, sensory properties as well as thermal and oxidation stability were analyzed. Moreover, volatile rancid off‐taste compounds were determined by HS‐SPME‐GC‐O/MS. Acrolein was measured by means of NTD‐GC‐MS. Six optimized deep‐frying fat prototypes were further investigated in a long‐term deep‐frying study using donut‐like products and quark balls as model bakery products. Most of the prototypes displayed high thermal stability as measured by total polar material (TPM) and polymerized triglycerides (PTG). Some of the deep‐frying fat blend prototypes performed equally well or even better than the virtually TFA free deep‐frying fats regarding oxidation stability. Several deep‐frying fat blend prototypes were similar to the TFA rich reference in most sensory attributes. These results were used to establish a deep‐frying fat toolbox that may be applied for further fat blend optimizations. Finally, this research data may contribute to endorse artisan bakeries to use only virtually TFA free deep‐frying fats for the production of deep‐fried bakery products. Practical applications: Many artisan bakeries in Germany still use deep‐frying fats containing partially hydrogenated peanut oils with high amounts of TFA. However, some have already replaced the deep‐frying fats by virtually TFA free alternatives. In order to encourage a more widespread application of virtually TFA free deep‐frying fats optimization of the latter in terms of their technofunctional and sensory properties is recommended. This research data may contribute to endorse artisan bakeries to use only virtually TFA free deep‐frying fats for the production of deep‐fried bakery products. Novel virtually TFA free deep‐frying fat blends were developed and characterized in terms of their technofunctional‐sensory properties. The final optimized six prototypes exhibited similar or partly even improved technofunctional‐sensory properties compared to commercially available deep‐frying fats intended for bakery applications.