Figen Korel

Antimicrobial Activity of Lactoperoxidase System Incorporated into Cross‐Linked Alginate Films

In this study, the antimicrobial effect of lactoperoxidase (LPS) incorporated alginate films was investigated on Escherichia coli (NRRL B-3008), Listeria innocua (NRRL B-33314), and Pseudomonas fluorescens (NRRL B-253) in presence of different concentrations of H(2)O(2) (0.2, 0.4, and 0.8 mM) and KSCN (1, 2, and 4 mM). The incorporation of 70 nmol ABTS/min/cm(2) LPS into alginate films gave 0.66 to 0.85 nmol ABTS/min/cm(2) enzyme activity at 0.2 to 0.8 mM H(2)O(2) concentration range. The antimicrobial activity of LPS system on target bacteria changed according to the concentrations of KSCN and H(2)O(2). The growth of all tested bacteria was prevented for a 6-h period by applying LPS system in presence of 0.4 or 0.8 mM H(2)O(2) and 4 mM KSCN. At 0.8 mM H(2)O(2) and 4 mM KSCN, the LPS system also inhibited growth of L. innocua and P. fluorescens for a 24-h incubation period, whereas E. coli growth could not be inhibited for 24 h under these conditions. At 0.2 mM H(2)O(2) and 1 to 4 mM KSCN, a considerable inhibitory effect was obtained only on P. fluorescens. The decreasing order of the resistance of studied bacteria to LPS system is as follows: E. coli, L. innocua, and P. fluorescens. The developed antimicrobial system has a good potential for use in meat, poultry, and seafood since alginate coatings are already used in these products. Further studies are needed to test the LPS incorporated edible films in real food systems.

Transportability of data between electronic noses: mathematical methods

Abstract Accumulation of databases containing volatile attributes of foods measured by electronic noses requires transportability of data between machines. Due to differences in each machine, or sensor drift, the same sample may result in slightly different readings. Three functions (coefficient, F1; coefficient with intercept, F2; matrix, F3) and two neural network configurations (NN1, NN2) were tried to assess their suitability for acceptable transformation. Two EEV electronic noses with identical sensors were used to read milk samples stored for up to 12 days. Six replicate readings were separated to ‘calibration’ (four replicates) and ‘unknown’ (two replicates) sets. Discriminant function analysis was applied to evaluate ‘unknowns’ in ‘calibration’ sets. When ‘old unknowns’ were converted and classified in ‘new calibrations’, correct classification rates (CCR) were 2/12, 3/12 and 7/12 for F1, F2 and F3, respectively. Also, neural networks were used to either transform one ‘calibration’ set to another (CCR=8/12 and 9/12), or to evaluate the ‘unknown’ sets in the ‘calibration’ sets (CCR=7/12). More research is needed in this area.

Quality Evaluation of Raw and Cooked Catfish (Ictalurus punctatus) Using Electronic Nose and Machine Vision

Abstract Current inspection of catfish quality relies upon sensory evaluation that can be subjective, prone to error and difficult to quantify. Fresh farm-raised catfish (Ictalurus punctatus) fillets were stored at 1.7_ and 7.2_C for up to 6 days and evaluated daily for changes in odors in the raw and cooked stage by an electronic nose as well as by trained sensory panelists. Aerobic microbial counts were performed. Color changes were measured by a color machine vision system. Electronic nose detected odor changes during storage at 1.7_ and 7.2_C. Color analysis showed changes during storage. Addition of color data to electronic nose readings improved quality discrimination among samples. Discriminant function analysis successfully correlated electronic nose sensor and color data with microbial levels, storage time, and sensory readings.

Composition, Color and Mechanical Characteristics of Pretreated Candied Chestnuts

Raw-peeled chestnuts were treated with citric acid or sodium metabisulphite, steamed, and dipped into sugar solutions containing dextrose and sucrose, or dextrose and fructose. Composition, mineral content, weight change, rheological properties, and color were measured at each step. Carbohydrate content increased during processing. Candied chestnuts were low in protein (1.31–1.35%) and lipids (0.29–0.78%) but high in carbohydrates (73.48–76.13%). Their mineral concentrations were: Ca 19.08–46.70, Cu 0.19–0.52, Fe 0.88–1.98, K 180.5–659.1, Mg 26.83–69.57, Mn 0.70–2.42, Zn 1.51–6.95 mg/100 g sample. Rheological properties were affected by processing steps. Dipping into sugar solutions did not affect rheological properties. Color changes were quantified, and average L*, a*, and b* values measured.

Odor Evaluation of Shrimp Treated with Different Chemicals Using an Electronic Nose and a Sensory Panel

ABSTRACT An electronic nose with 12 conducting polymer sensors was used to measure odors of raw shrimp treated with different chemicals. Headless shell-on pink shrimp (Pandalus jordani) were treated with bleach (0, 25, 50, 100 and 200 ppm), phosphates (0, 2, 4 and 6% w/v) and sulfites (0, 0.75, 1.25 and 2% w/v) and stored at 2°C for 48 hours. Odors were evaluated by sensory panels and an electronic nose. Aerobic plate counts were performed. Discriminant function analysis was used as the pattern recognition technique to differentiate samples based on odors. Results showed that the electronic nose could discriminate differences in odor due to chemicals present in shrimp. The correct classification rates for bleach, phosphate and sulfite treated shrimp were 92.7, 95.8, and 99.2%, respectively.

Physicochemical, textural, volatile, and sensory profiles of traditional Sepet cheese

Characterization of traditional cheeses is important for the protection of diversity of tradition and contributing baseline data for further research and quality control. Sepet cheese is a traditional cheese and specific to the Aegean region of Turkey. In this study, 52 Sepet cheese samples were analyzed to characterize the physicochemical, textural, volatile compounds, and sensory profiles. The changes in the physicochemical and volatile compositions were investigated during production and ripening periods. The average dry matter (DM; 55.16%), fat-in-DM (45.80%), protein (29.18%), salt-in-DM (12.88%), water activity (0.83), pH (5.50), titratable acidity (1.69%), ripening and lipolysis indices (11.06 and 6.36), firmness (212.20N), springiness (0.62), cohesiveness (0.57), adhesiveness (0.48 Nmm), and chewiness (66.87N) values of Sepet cheese samples were determined. Hexanoic, octanoic, decanoic, and butyric acids, which were responsible for the cheesy, waxy, goaty odors, were the most abundant volatile compounds in these cheeses. Most of the volatile compounds increased significantly during production and ripening. Significant changes in most of the physicochemical characteristics were observed up to the third month of ripening. As a result of the descriptive sensory analysis, Sepet cheeses were described with descriptors such as free fatty acid, animal like, sulfurous, creamy, cooked, and whey, and aromatics with high salty basic taste.

Impact of preharvest and postharvest alginate treatments enriched with vanillin on postharvest decay, biochemical properties, quality and sensory attributes of table grapes

Alginate solution enriched with vanillin as a bioactive compound was investigated for improving preharvest and postharvest quality and safety of table grapes. Alginate treatments with or without vanillin as preharvest spray and postharvest coating were implemented on table grapes of Alphonse Lavalleé and Razaki cultivars. Fungal decay, biochemical properties, quality and sensory attributes were evaluated at day of preharvest treatment, at harvesting and during 35days of storage at 4±2°C. Alginate treatments with or without vanillin were effective in preventing weight and firmness losses. Total soluble solids, titratable acidity, and color of grapes coated with alginate coatings with or without vanillin showed minor changes compared to control grapes. Alginate coating incorporating vanillin provided significant reduction (1.73log CFU/g) in yeast-mold growth. Moreover, the coatings maintained greater total phenolic content and antioxidant activity compared to others during postharvest storage. In terms of sensory attributes, appearance was ranked as the highest for alginate coating without vanillin due to glossiness of alginate.

Quantification of Staphylococcus aureus in white cheese by the improved DNA extraction strategy combined with TaqMan and LNA probe-based qPCR.

Four different bacterial DNA extraction strategies and two different qPCR probe chemistries were studied for detection of Stapylococcus aureus from white cheeses. Method employing trypsin treatment followed by a commercial kit application and TaqMan probe-based qPCR was the most sensitive one detecting higher counts than standards in naturally contaminated samples.

Control of lactic acid bacteria in fermented beverages using lysozyme and nisin: test of traditional beverage boza as a model food system

The objective of this study was to increase quality and limited shelf-life of boza (3–15 days), a traditional Balkan origin fermented beverage using lysozyme (LYS) and/or nisin (NIS). For this purpose, the effectiveness of NIS, LYS and LYS:NIS combinations was first tested in a broth medium at 4 °C for 3 weeks on Lactobacillus plantarum, one of the frequently isolated lactic acid bacteria in boza. Stability of LYS and NIS in boza, their effects on LAB counts, and chemical and sensory properties of boza were then evaluated during cold storage at 4 °C. Results of LAB counts as well as pH, Dand L-lactic acid, and titratable acidity measurements showed that LAB in boza containing NIS (250 lg g ) or LYS:NIS (500:250 lg g ) could be controlled without reducing LAB counts below 6 log CFU mL 1 during 2 weeks shelf-life. In contrast, LYS (500 lg g ) alone could not control LAB in boza to delay its acidic spoilage. Positive effects of NIS and LYS:NIS application on quality of boza were also proved with sensory analysis by panelists and e-nose measurements. This work showed that use of natural GRAS agents in preservation of fermented beverages containing probiotic LAB is possible without affecting their characteristic aroma and flavour.