Figen Kaymak-Ertekin

Moisture sorption isotherm characteristics of peppers

Abstract Moisture sorption isotherms of green and red peppers were determined at three different temperatures (30°C, 45°C and 60°C) and relative humidities (10–90%), using the standard static, gravimetric method. The GAB, Halsey, Oswin and BET sorption models were tested to fit the experimental data. A nonlinear regression analysis method was used to evaluate the constants of four sorption equations. The Halsey equation gave the best fit to the experimental sorption data for a wide range of water activity while BET gave the best fit for a water activity range of 0.1–0.5. The agreement between experimental and calculated values was found to be satisfactory. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures using the Clasius–Clapeyron equation.

Effect of steam baking on acrylamide formation and browning kinetics of cookies.

UNLABELLED Effects of baking method and temperature on surface browning and acrylamide concentration of cookies were investigated. Cookies were baked in natural and forced convection and steam-assisted hybrid ovens at 165, 180, and 195 °C and at different times. For all oven types, the acrlyamide concentration and surface color of cookies increased with increasing baking temperature. Significant correlation was observed between acrylamide formation and browning index, BI, which was calculated from Hunter L, a, and b color values, and it showed that the BI may be considered as a reliable indicator of acrylamide concentration in cookies. Acrylamide formation and browning index in cookies were considered as the first-order reaction kinetics and the reaction rate constants, k, were in the range of 0.023 to 0.077 (min(-1) ) and 0.019 to 0.063 (min(-1) ), respectively. The effect of baking temperature on surface color and acrylamide concentration followed the Arrhenius type of equation, with activation energies for acrylamide concentration as 6.87 to 27.84 kJ/mol; for BI value as 19.54 to 35.36 kJ/mol, for all oven types. Steam-assisted baking resulted in lower acrylamide concentration at 165 °C baking temperature and lower surface color for all temperatures. Steam-assisted baking is recommended as a healthy way of cooking providing the reduction of harmful compounds such as acrylamide for bakery goods, at a minimal level, while keeping the physical quality. PRACTICAL APPLICATION The kinetics of acrylamide formation and browning of cookies will possibly allow definition of optimum baking temperatures and times at convectional and steam-assisted baking ovens. The kinetic model can be used by developing baking programs that can automatically control especially a new home-scale steam-assisted hybrid oven producing healthy products, for the use of domestic consumers.

Effects of spray-drying conditions on the chemical, physical, and sensory properties of cheese powder

Dairy powders are produced to increase the shelf life of fresh dairy products and for use as flavoring agents. In this study, 24 cheese powders produced under 7 different conditions were used to investigate the effects of spray-drying parameters (e.g., inlet air temperature, atomization pressure, and outlet air temperature) on the quality of white cheese powder. Composition, color, physical properties, reconstitution, and sensory characteristics of white cheese powders were determined. The results revealed that the white cheese powders produced in this study had low moisture content ratios and water activity values. High outlet air temperatures caused browning and enhanced Maillard reactions. Additionally, high outlet air temperatures increased wettability and dispersibility and decreased the solubility of white cheese powders. Free fat content was positively correlated with inlet air temperature and negatively correlated with outlet air temperature and atomization pressure. Sensory analyses revealed that white cheese powder samples had acceptable sensory characteristics with the exception of the sample produced at an outlet air temperature of 100°C, which had high scores for scorched flavor and color and low scores for cheese flavor.

The Effect of External Mass Transfer Resistance during Drying of Fermented Sausage

The drying mechanism of fermented sausages (sucuks) that were cylindrical rod shaped, 40 cm long and 4 cm diameter, during ripening under natural convection conditions at different temperatures (15 to 30°C) was examined. To simulate the experimental drying curves, three empirical models and a diffusional model assuming negligible external mass transfer resistance were evaluated. The drying rate curves of sucuk samples were also simulated taking into account the influence of the external mass transfer resistance. The equation was solved using the trial-and-error solution algorithm developed in this study and the mass transfer coefficient, k c , and effective moisture diffusivity, D eff , were simultaneously determined (1.44 × 10−8 to 1.93 × 10−8 m/s and 4.30 × 10−10 to 6.85 × 10−10 m2/s, respectively). The proposed model considering the effect of external resistance allowed the accurate simulation of the experimental drying data of sucuks at different temperatures.

Effect of Steam-Assisted Hybrid Cooking on Textural Quality Characteristics, Cooking Loss, and Free Moisture Content of Beef

Semitendinosus muscles were cooked in a steam-assisted hybrid oven and also convection ovens at three different oven temperatures (180, 210, and 240°C) until three different end point temperatures [65°C (medium-rare), 72°C (medium), 80°C (medium-well)] were reached. Textural properties of cooked beef were investigated by the Warner Bratzler shear test and texture profile analysis. Cooking loss and free moisture content of muscle tissue was determined for each cooking condition. In addition, sensory analysis was carried out in order to compare with the instrumental results and correlations between instrumental texture parameters and sensory results. Steam-assisted hybrid oven cooking of beef resulted in a tougher texture, higher cooking loss, and lower free moisture content than convection cooking. High correlation coefficients (r2 > 0.70) were observed between instrumental texture measurements and sensory results for all ovens, especially in terms of tenderness. The free moisture content and adhesiveness values were also correlated well with juiciness (r2 > 0.70) for all oven types.

Effects of Formulation on Stability of Spray-Dried Egg

Moisture adsorption isotherms of spray-dried whole egg, microencapsulated with gelatin (G), lactose (L), pullulan (P), and their mixtures at equal ratios (gelatin + lactose [GL] and gelatin +pullulan [GP]), were determined using the standard static-gravimetric method at 25°C. The data were fitted to the various sorption models and the constants were estimated by nonlinear regression analysis. Among the sorption models tested, the Guggenheim-Andersen-de Boer (GAB) and Ferro Fontan equations were recommended for characterizing the adsorption behavior of spray-dried whole egg, either microencapsulated or unencapsulated, in the water activity range of 0.11–0.84. It was indicated that all of the egg powders were stable up to a water activity of 0.43. The oxidative stability of microencapsulated powders was investigated under storage conditions of 20°C and 50% relative humidity (RH). The microencapsulation process resulted in a decrease in the cholesterol oxidation level of egg powder during storage, where it followed a zero-order reaction kinetics and the t rej value representing the time required to reach total cholesterol oxidation products (TCOP) = 384.2 µg/g egg fat as the upper limit of acceptability for fat oxidation was calculated as 1,124 days at 20°C for egg powder microencapsulated with lactose. The relations among glass transition temperatures, oxidation rate constants, and monolayer moisture content values obtained by the GAB model are also highlighted.

Steam Assisted Hybrid Cooking Behavior of Semitendinosus Muscle: Heterocyclic Amines Formation, Soluble Protein Degradation, Fat Retention, Surface Color, and Cooking Value

Beef (Semitendinosus muscle) was cooked in natural convection, forced convection and steam assisted hybrid oven and saturated steam oven at different oven temperatures until the geometric center of samples reached different end temperatures. Heterocyclic amine (HCA) compounds formation, soluble protein degradation kinetics, cook value, changes in fat content, surface colour and overall acceptance of cooked beef were determined. Soluble protein degradation of beef was considered as first order reaction kinetics and the reaction rate constants, k, were determined in the range of 0.014-0.052 min−1. In steam assisted hybrid oven had higher reaction rate constants compared to that of the convection ovens. The effect of cooking temperature on soluble protein degradation for natural convection, forced convection and steam assisted hybrid oven followed the Arrhenius type of equation with activation energies of 12.45, 14.57 and 60.16 kJ/mol, respectively. Lower HCAs contents, shorter cooking times, lower cook values and lower fat retention were obtained by steam assisted hybrid oven cooking. Steam assisted hybrid cooking could be considered as an alternative cooking method to obtain a healthier product without compromising the eating habits of conventional methods due to better appearance (moderate burned surface) than saturated steam oven samples and a product retaining the most of the nutritional values.

EFFECTS OF DIFFERENT FREEZING AND THAWING METHODS INCLUDING PRETREATMENTS ON QUALITY ATTRIBUTES OF MANDARIN AND STRAWBERRY

In this study, the effects of pretreatments, freezing and thawing methods on the quality of mandarin and strawberry were investigated. Individual quick freezing (IQF,-15oC) and conventional static methods (18oC and -24oC) were applied as freezing methods while immersing sugar and citric acid solutions as pretreatments. Thawing was carried out in a refrigerator (4oC, 4 hours) and in a microwave (2 min). The color and texture of the samples improved and the drip loss after freezing decreased with immersing into sugar solution before freezing. Immersion into citric acid were found a better way to protect vitamin C after thawing. Quick-freezing significantly reduced the drip loss compared to conventional freezing. Microwave thawing is superior to thawing in the refrigerator considering drip losses. The fast freezing method, IQF is emphasized by reducing time and quality losses.

Natural Food Colorants Obtained from Algae and Their Functional Properties

Colour is one of the major features that fascinate the customers and makes the foods more allurement. Due to changes of customer demands and countries’ legislations, usage of synthetic colorants is being decreased every day and food industry tends to use natural colorant. Algae have recently gained importance owing to a sustainable natural source of colorant. Algae can rapidly increase their biomass compared to plants thus they produce more pigments. This review covers the subjects about the functional properties and usage areas of natural colorants obtained from algae; phycocyanin, phycoerythrin, astaxanthin, canthaxanthin, β-carotene, lutein, fucoxanthin.

Kinetics of colour, chlorophyll, and ascorbic acid content in spinach baked in different types of oven

ABSTRACT Spinach was baked in steam-assisted hybrid ovens, natural and forced convection ovens, and saturated steam ovens at different temperatures and baking times. The moisture content, water activity, peroxidise activity, colour, ascorbic acid, and chlorophyll content were determined for each baking time and kinetic analysis of thermal degradation of the colour, chlorophyll, and ascorbic acid were evaluated. Degradation of green colour, total chlorophyll, and ascorbic acid in spinach leaves during the baking process was considered as first order reaction kinetics and temperature dependency of degradation was described by the Arrhenius equation. Baking in steam-assisted hybrid ovens resulted in the highest rate of reaction for both colour change and chlorophyll degradation, followed by forced convection and then natural convection ovens. The existence of steam in the baking chamber resulted in an acceleration of the baking process and better ascorbic acid retention in spinach was determined by baking in steam-assisted hybrid ovens. Degradation kinetics could allow definition of optimum baking temperatures and times in different types of ovens and shorter baking times should be preferred in steam-assisted hybrid ovens if fresh appearance (high greenness) is desired.