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.     

Flavour Changes in Asian White Radish (Raphanus sativus) Produced by Different Methods of Drying and Salting

Asian white radish pieces were dried to < 10% moisture using a hot air drier, a heat pump drier and a freeze drier, and whole roots were partially dried by salting under pressure with sodium chloride. The level of the primary flavor compound, 4-methylthio-3-trans-butenyl isothiocyanate (MTBITC), decreased in all treatments. Freeze-dried white radish showed the lowest loss of about 15% MTBITC. Radish dried with hot air and heat pump driers showed increasing MTBITC loss with increasing drier temperature with a lower loss in the heat pump drier at equivalent temperatures with the rate of drying also faster with the heat pump drier. Osmotic dehydration with salt caused a substantial loss of MTBITC with the loss increasing with increasing salt concentration. Use of 5% salt resulted in the lowest loss of MTBITC while achieving an acceptable rate of water loss.     

A study on degradation kinetics of ascorbic acid in drumstick (Moringa olifera) leaves during cooking

The kinetics of ascorbic acid degradation in drumstick (Moringa olifera) leaves as well as in pure ascorbic acid solutions at the initial concentrations present in drumstick leaves over a temperature range of 50–120 °C (isothermal temperature process) has been studied. The degradation kinetics of ascorbic acid was also evaluated in normal open‐pan cooking, pressure‐cooking and a newly developed and patented fuel‐efficient eco cooker (non‐isothermal heating process). The ascorbic acid degradation followed first‐order reaction kinetics where the rate constant increased with an increase in the temperature. The temperature dependence of degradation was adequately modelled by the Arrhenius equation. A mathematical model was developed using the isothermal kinetic parameters obtained to predict the losses of ascorbic acid from the time–temperature data of the non‐isothermal heating/processing method. The results obtained indicate the ascorbic acid degradation is of similar order of magnitude in all the methods of cooking. Copyright © 2005 Society of Chemical Industry     

Effect of pH and temperature on the thermostability of prickly pear (Opuntia ficus‐indica) yellow‐orange pigments

The colour stability of the yellow‐orange pigment (λ_max = 476 nm) of prickly pear (Opuntia ficus‐indica) fruit was determined as a function of temperature and pH. The experiments were carried out at three different temperatures (50, 70 and 90°C) with pigment solutions at pH values ranging from 2–7. The degree of pigment retention decreased with increasing temperature as a function of increasing thermal exposure time with least pigment degradation at pH 5. The reaction rate constants were determined as 0.0062, 0.0383 and 0.1102 min^–1 for a thermal degradation reaction rate of pseudo‐first order. The activation energy was calculated as 65.1 kJ·mol^–1.     

Resistance of thermally modified ash (<Emphasis Type="Italic">Fraxinus excelsior</Emphasis> L.) wood under steam pressure against rot fungi,soil-inhabiting micro-organisms and termites

Thermal modification processes have been developed to increase the biological durability and dimensional stability of wood. The aim of this paper was to study the influence of ThermoWood^® treatment intensity on improvement of wood decay resistance against soil-inhabiting micro-organisms, brown/white rots and termite exposures. All of the tests were carried out in the laboratory with two different complementary research materials. The main research material consisted of ash (Fraxinus excelsior L.) wood thermally modified at temperatures of 170, 200, 215 and 228 °C. The reference materials were untreated ash and beech wood for decay resistance tests, untreated ash wood for soil bed tests and untreated ash, beech and pine wood for termite resistance tests. An agar block test was used to determine the resistance to two brown-rot and two white-rot fungi according to CEN/TS 15083-1 directives. Durability against soil-inhabiting micro-organisms was determined following the CEN/TS 15083-2 directives, by measuring the weight loss, modulus of elasticity (MOE) and modulus of rupture (MOR) after incubation periods of 24, 32 and 90 weeks. Finally, Reticulitermes santonensis species was used for determining the termite attack resistance by non-choice screening tests, with a size sample adjustment according to EN 117 standard directives on control samples and on samples which have previously been exposed to soil bed test. Thermal modification increased the biological durability of all samples. However, high thermal modification temperature above 215 °C, represented by a wood mass loss (ML%) due to thermal degradation of 20%, was needed to reach resistance against decay comparable with the durability classes of ‘‘durable’’ or ‘‘very durable’’ in the soil bed test. The brown-rot and white-rot tests gave slightly better durability classes than the soil bed test. Whatever the heat treatment conditions are, thermally modified ash wood was not efficient against termite attack neither before nor after soft rot degradation.     

Mechanisms of Docosahexaenoic and Eicosapentaenoic Acid Loss from Pacific Saury and Comparison of Their Retention Rates after Various Cooking Methods

The docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) contents of Pacific saury (Cololabis saira), a fatty fish and staple of the Japanese diet, have been reported to decrease after cooking. This study compared the DHA and EPA contents remaining in saury after grilling, pan‐frying or deep‐frying to center temperatures of 75, 85, or 95 °C, and examined physical loss, lipid oxidation, and thermal degradation as mechanisms of DHA and EPA loss. Temperature changes inside the saury were monitored using thermocouples, while DHA and EPA contents, oxygen radical absorbance capacity, and measurements of lipid oxidation (that is, carbonyl value and thiobarbituric acid value) were determined chemically. Visualization of temperature distribution inside fish samples during cooking revealed large differences in heat transfer among cooking methods. True retention rates in grilled (DHA: 84 ± 15%; EPA: 87 ± 14%) and pan‐fried samples (DHA: 85 ± 16%; EPA: 77 ± 17%) were significantly higher than deep‐fried samples (DHA: 58 ± 17%; EPA: 51 ± 18%), but were not affected by final center temperatures despite differences in cooking times. Physical loss via cooking losses (grilling and pan‐frying) or migration into frying oil (deep‐frying) accounted for large quantities of DHA and EPA loss, while lipid oxidation and thermal degradation did not appear to be major mechanisms of loss. The antioxidant capacity of saury was not significantly affected by cooking treatments. The results of this study suggest that minimization of physical losses during cooking may increase DHA and EPA contents retained in cooked Pacific saury.     

Kinetics of 3-chloropropane-1,2-diol (3-MCPD) degradation in high temperature model systems

A study of the decay kinetics of 3-chloropropane-1,2-diol (3-MCPD) at high temperatures in aqueous model systems is reported. Data obtained over the pH range 5-6.5 and temperatures of 80-142 °C agreed well with a predicative model derived from earlier kinetic data. The results showed that 3-MCPD was unstable in aqueous solutions approaching infinite dilution at temperatures above 80 °C. Comparison of the experimental decay of 3-MCPD with that based on the kinetic parameters A (=10^{7.73347+0.83775pH}s-1) and E_a (=119.2 kJ mol^-1) was good to within 20% over the temperature and pH ranged studied. A putative mechanism for the degradation reaction is discussed together with the implications for the decay and formation of 3-MCPD in food systems.     

Changes in the Tenderness of Meat Cooked at 50–65°C

Warner-Bratzler (WB) shear force values obtained for stretched veal muscles decreased as cooking temperatures were increased from 50 to 60°C. Increased proteolytic enzyme activity at these temperatures to give accelerated aging did not appear to explain the effects since there was still a substantial decrease in shear force with increase in cooking temperature from 50 to 60°C, even when well aged (7 wk at 5–6°C) meat and meat cooked for 24 hr was used. A more likely explanation was that, even at these relatively low temperatures, changes in connective tissue were involved since (a) the magnitude and direction of the change in shear force with increasing temperature was dependent on animal age and cooking time; (b) the effect of recooking at 80°C was dependent on animal age; and (c) the effects of increasing the cooking temperature and/or time on adhesion between the meat fibres was significantly greater for the samples from the younger animals.     

Sorption studies of Zn(II)- and Cd(II)ions from aqueous solution on treated sawdust of sissoo wood

Sawdust, an inexpensive material, has been utilized as an adsorbent for the removal of Zn(II)- and Cd(II)ions from aqueous solution. The effects of time of equilibrium, pH, temperatures and dosage of the adsorbent on the removal of Zn(II)- and Cd(II)ions have been studied. The equilibrium nature of Zn(II)- and Cd(II)ions adsorption at different temperatures (25–60 °C) has been studied. The percent adsorption of Zn(II)- and Cd(II)ions increased with an increase in pH, temperature and dosage of treated sawdust. The applicability of the Langmuir isotherm suggests the formation of monolayer coverage of Zn(II)- and Cd(II)ions at the surface of the adsorbent. The thermodynamic parameters like free energy, enthalpy and entropy changes for the adsorption of Zn(II)- and Cd(II)ions has also been computed and discussed. The heat of adsorption [ΔH=17.706 kJmole^-1 for Zn(II) and ΔH=16.949 kJmole^-1 for Cd(II)] implied that the adsorption was an endothermic adsorption. The sawdust was found to be a metal adsorbent as effective as activated carbon.     

Effects of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens)

BACKGROUND: The main objective of this research was to determine changes in nutrient content of two African leafy vegetables, Cassia tora and Corchorus tridens, on cooking and storage under different temperature conditions, i.e. room storage (20 °C), refrigerated storage (4 °C) and frozen storage (?18 °C). RESULTS: The leafy vegetables were analysed for moisture, colour (Hunter L, a, b), texture, total chlorophyll, ascorbic acid, dehydroascorbic acid and total phenolics. Results indicated that the degradation of ascorbic acid was highest as a result of frozen storage, followed by room temperature storage. The dehydroascorbic acid content was correspondingly high in frozen stored leafy vegetables, whereas it was undetectable in the room temperature and refrigerated stored materials. The total phenolic content of the leaves increased with storage time while the total chlorophyll content decreased under all storage conditions. Domestic cooking resulted in significant additional losses of ascorbic acid following storage under all temperature conditions, with only 1–10% retention in the leaves and 50–60% retention in the cooking water. The green colour of the leafy vegetables was retained best under refrigerated and frozen storage, while the peak force and toughness of the leaves increased upon storage under all conditions. The moisture content of the leafy vegetables did not show any significant difference on storage. CONCLUSION: This study is one of few to report nutrient content changes on the same raw material stored under various temperature conditions and cooked domestically. Refrigerated storage resulted in the highest retention of ascorbic acid and green colour in the leafy vegetables. Copyright © 2009 Society of Chemical Industry     

A study on degradation kinetics of riboflavin in green gram whole (Vigna radiata L.)

The kinetics of riboflavin degradation in green gram whole (Vigna radiata L.), as well as in pure riboflavin solutions, at initial concentrations present in green gram were studied over a temperature range of 50–120 °C (steady state temperature process). Riboflavin degradation followed first order kinetics, where the rate constant increased with an increase in the temperature. The temperature-dependence of degradation was adequately modelled by the Arrhenius equation. The degradation kinetics of riboflavin, in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient `Eco-cooker', were also studied (unsteady state heating process). A mathematical model, to predict the losses of riboflavin from the time–temperature data of the unsteady state heating/cooking process, has been developed using the steady state kinetic parameters obtained. The results indicate riboflavin degradation of a similar magnitude in all three modes of cooking used in the study.     

Enhancement of Corn Nixtamalization by Power Ultrasound

Nixtamalization, a key production step for masa flour used for tacos, corn tortillas, and chips, traditionally involves corn kernel cooking for 1 h and a lengthy process of steeping (16–18 h) in a lime solution. This study aimed at accelerating the traditional nixtamalization (TN) process using power ultrasound with acoustic energy density around 1.85 W/g for 1 h during cooking followed by brief steeping for 1 h. The cooked kernels (nixtamal) were evaluated for texture and color, while the cooking liquor (nejayote) was evaluated for solid losses. The power ultrasound-assisted nixtamalization resulted in significantly (p?≤?0.05) reduced process time and softer nixtamal with less solid losses in nejayote than control (TN). Response surface methodology established significant relationships of sonication duration and cooking temperature to texture, color of nixtamal, and dry matter loss in nejayote. This study indicates that power ultrasound ameliorated traditional nixtamalization in terms of quality and operation time.     

Effects of Different Drying Conditions on Water Absorption and Gelatinization Properties of Pasta

Three flat pasta types dried by low temperature (LT), high temperature (HT), and very high temperature (VHT) drying profiles were analyzed. The starch properties of these pastas, cooked at different temperatures for different times, were investigated. The starch properties were examined by observing starch swelling with a scanning electron microscope (SEM), identifying the phase difference with an ultrasonic device, and determining the water absorption and gelatinization rate with the BAP method and X-ray diffraction. The SEM images revealed expanded and gelatinized starch granules during cooking pasta and increased with drying temperature. The water absorption of pasta increased with cooking temperatures and times, and the trend was LT > HT > VHT-dried pasta. The gelatinization rate of pasta increased with cooking time and temperature. The X-ray diffractograms of pasta cooked less than 12 min showed typical A-type X-ray diffraction patterns, while in pasta cooked for 12 min, V-type diffraction was observed. Uncooked pasta showed an enhanced peak at about 2θ?=?20°, which indicated the generation of high levels of amylose–lipid complexes. The present study found that these changes occurred during drying and may affect pasta starch characteristics.     

Changes in Shear Parameters,Protein Degradation and Ultrastructure of Pork Following Water Bath and Ohmic Cooking

The objective of this study was to investigate the effects of ohmic (OH) and water bath (WB) cooking on shear parameters, protein degradation and ultrastructure changes of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range, 20–100 °C). The cooking loss and Warner–Bratzler shear force of the OH-cooked meat were significantly lower (P?<?0.05) while protein solubility, pH and endothermic transition temperature were higher than those obtained by WB cooking at the same EPTs (range, 20–80 °C). Sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis showed that during OH cooking, the meat had slightly fainter protein bands than that of WB-cooked ones. Less obvious shrinkage of the sarcomere and loss in the structure of Z discs were detected especially in OH-cooked meat at EPTs (100 °C). Strong correlations among pH, cooking loss, Warner–Bratzler shear force, sarcoplasmic protein solubility, T _max2, and T _max3 were observed in meat following OH cooking.     

Efficacy of novel organotin(IV) complexes on non-durable tropical wood against decay fungi

Interest in organotin(IV) compounds is increasing due to their interesting structural features and possession of biological activities. The objective of this study was to determine the efficacy of novel organotin(IV) complexes against Trametes versicolor and Gloeophyllum trabeum decay fungi. Soil block decay test was performed using T. versicolor and G. trabeum for 16 weeks. Ten 19 × 19 × 19 mm³ sized wood cubes of Alstonia scholaris, Macaranga triloba and Hevea brasiliensis were treated with three levels of concentration (0.1, 0.5 and 1 %) of monomethyltin(IV) (MMT) and monophenyltin(IV) (MPT) of monosubstituted organotin(IV) and dimethyltin(IV) (DMT), diphenyltin(IV) (DPT) and dibutyltin(IV) (DBT) of disubstituted organotin(IV) complexes with 2-acetylpyridine-N(4)-cyclohexyl thiosemicarbazone (APCT) ligand and their respective retention uptake was determined. The best protection against decay fungi was provided by dibutyltin(IV) complex followed by diphenyltin(IV), dimethyltin(IV), monophenyltin(IV) and monomethyltin(IV) complexes with mean weight loss ranging from 4 to 5, 5 to 7, 8 to 9, 10 to 11 and 14 to 19 percent, respectively while the weight loss of the untreated wood cubes varied from 51 to 65 %. Wood densities decreased with increased weight loss. Density reduction of monosubstituted organotin(IV) treated wood cubes was higher than disubstituted organotin(IV) treated wood cubes. Soil block test showed that selected organotin(IV) complexes are effective and among all of them dibutyltin(APCT) complex gave the best protection against the tested T. versicolor and G. trabeum decay fungi.     

Effect of processing on water absorption and softening kinetics in chickpea (Cicer arietinumL) seeds

The processing effect on the physical properties of chickpea seeds (kabuli type cv Athenas) is reported. Soaking of chickpea seeds in different solutions (distilled water, 0·5% NaHCO₃ and 0·5% CaCl₂) is characterised by a rapid water absorption followed by a decrease in the hydration rate to saturation point. An improvement in chickpea softening rate and water absorption during cooking, with previous 12 h soaking in 0·5% NaHCO₃, was observed. The presence of Ca²⁺ ions delayed the softening process in chickpea seeds. Physicochemical changes associated to the soaking and cooking process necessary for reducing cooking time are discussed. The texturometer method was estimated as a suitable objective method for the evaluation of the cooking degree in chickpea seeds. © 1998 Society of Chemical Industry     

Seasonality of the Thermal Kinetics of Color Changes in Whole Spinach (Spinacia Oleracea) Leaves Under Pasteurization Conditions

Color changes in whole spinach (Spinacia oleracea) leaves at pasteurization temperatures (65 to 90°C) indicate that the parameter of “greenness” (-a_t/b_t) increased during a short initial period of heating, followed by a loss that was more pronounced at higher temperatures. Seasonality was evident in kinetic models for color changes possibly due to seasonal difference in chemical composition influencing color degradation kinetics. The mechanism for loss of greenness at lower temperatures was attributed to enzymatic activity while cell collapse, cell compaction, and oxidative changes were probably more important at higher temperatures. Lower temperatures resulted in a higher retention of green color of spinach leaves during the thermal pasteurization process and the kinetic models presented in this work could be used for optimizing pasteurization processes.     

Effect of pH and temperature on the thermostability of prickly pear (Opuntia ficus-indica) yellow-orange pigments

The colour stability of the yellow-orange pigment (lambda max = 476 nm) of prickly pear (Opuntia ficus-indica) fruit was determined as a function of temperature and pH. The experiments were carried out at three different temperatures (50, 70 and 90 degrees C) with pigment solutions at pH values ranging from 2-7. The degree of pigment retention decreased with increasing temperature as a function of increasing thermal exposure time with least pigment degradation at pH 5. The reaction rate constants were determined as 0.0062, 0.0383 and 0.1102 min-1 for a thermal degradation reaction rate of pseudo-first order. The activation energy was calculated as 65.1 kJ.mol-1.     

Hard‐to‐cook tendency of chickpea (Cicer arietinum L) varieties

Chickpeas (Cicer arietinum L) develop the hard‐to‐cook (HTC) defect during storage at high temperatures (>25 °C) and high relative humidities (RH>65%). The objective of this work was to assess the tendency of chickpea varieties to become HTC. Three samples of chickpeas (Surutato 77, Mocorito 88 and Blanco Sinaloa 92) were grown under irrigation conditions. Two hardening procedures were used: (1) storage hardening—samples were stored at 33–35 °C and 76% relative humidity for 160 days; (2) chemical hardening—materials were soaked in 0.1 M acetate buffer (pH 4.0) at 37 °C for 1–7 h. The cooking time curves generated by chemical hardening had shapes similar to those obtained by storage hardening; both procedures were equally capable of discriminating chickpea varieties based on their susceptibility to develop the HTC condition. Chemical hardening might be useful for screening new chickpea varieties; its advantage over the storage method is its rapidity. © 2001 Society of Chemical Industry     

Kinetics of Quality Changes of Shrimp (<Emphasis Type="Italic">Litopenaeus setiferus</Emphasis>) During Pasteurization

Effect of cooking between 1 and 80 min at 60 to 100 °C on several quality attributes of whole peeled shrimp (Litopenaeus setiferus) (80–90 counts/kg) was studied using an isothermal heating method. Cook loss, area shrinkage, and hardness of shrimp increased with increasing heating time and temperature, following a fractional first-order kinetic model with activation energies (E _a ) of 71.0, 53.3, and 29.9 kJ/mol, respectively. Cook loss, area shrinkage, and hardness were positively correlated. The toughness of shrimp muscle increased in the initial period of heating, then decreased in the later period during the treatments. The overall color change (ΔE) increased with increasing treatment time and temperature, and followed a zero kinetic model with an E _a of 37.2 kJ/mol. The kinetic parameters obtained from this study can be applied toward understanding and predicting shrimp-quality changes during pasteurization treatments, and further provides insight into the pasteurization conditions required to achieve safe and high-quality shrimp products and potentially other crustacean shellfish and seafood products.