Kazuhito Kajiwara

CRYSTALLINE AND AMORPHOUS PHASES IN THE BINARY SYSTEM WATER-RAFFINOSE

The melting points, glass transitions and enthalpies of fusion of crystalline hydrates in binary water–raffinose mixtures have been studied by differential scanning calorimetery (DSC) over the accessible composition range. X-Ray diffraction was used to identify the crystalline forms. From the liquidus and solidus curves and shapes of the DSC scans, a raffinose trihydrate has been identified, and lower hydrates are also believed to exist. The melting points and enthalpies of fusion of raffinose pentahydrate and trihydrate are 352.7±0.1 K, 88.0±0.4 kJ mol -1 and 358.4 K, 47.6 kJ mol -1 , respectively. In the phase coexistence curve at higher raffinose concentrations a minimum point is observed, which is thought to be the eutectic of trihydrate and a lower hydrate. The raffinose mole fraction of the eutectic is 0.347, and its melting point and enthalpy of fusion are 356.6 K and 51.4 J g -1 . The raffinose mole fraction of the ice–pentahydrate eutectic is 7.9×10 -3 , and its melting point and enthalpy of fusion are 270.4±0.2 K and 237.6±0.5 J g -1 , respectively. The glass-transition profile for the binary system has been measured over the experimentally accessible composition range and the data fitted to the Gordon–Taylor equation, from which the glass-transition temperature for anhydrous raffinose is obtained as 376.4 K. Rehydration and recrystallisation rates of anhydrous, amorphous raffinose taking place during storage over media of constant relative humidity have been studied by measurements of shifts in the glass-transition and melting temperatures. The kinetics of water uptake, and of the subsequent crystallisation of raffinose pentahydrate from the amorphous substrates, show a complex dependence on relative humidity and temperature, which requires further study.

Characterization of deep-fat frying in a wheat flour-water mixture model using a state diagram.

BACKGROUND Crispness is an important characteristic to be controlled in deep-fat fried products. The physical state of food polymers influences the development of cellular structure and textural qualities of fried food. Glassy state is believed to play an important role in the mechanical properties of low-moisture food. Therefore, an understanding of the physicochemical phenomena in the development of fried food structure using a state diagram of the frying process is discussed. RESULTS Wheat flour models containing 400 and 600 g kg(-1) initial moisture content were fried in frying oil at 150 °C for 1-7 min. Thermal properties of wheat flour, structure alteration and textural properties of fried samples were evaluated. The porous structure continuously enlarged when the sample was in the rubbery state. As the frying time was prolonged, the state of the product became glassy due to a decrease in water content, resulting in the ceasing of porous enlargement. CONCLUSION The results revealed that physicochemical changes during frying influence the alteration of microstructure and quality of fried food, and the state diagram could be applied to explain the formation of microstructure during the frying process and used as a decision-making tool to choose the proper conditions to provide desirable qualities in fried food. Copyright

Equations for spectrophotometric determination of relative concentrations of myoglobin derivatives in aqueous tuna meat extracts

The percentage of metmyoglobin (%metMb) in aqueous meat extracts of bigeye and bluefin tuna and beef samples were estimated using previously reported equations derived from the absorption spectra of horse Mb. The results demonstrate that in an aqueous extract, the difference in %metMb estimated by the different equations was negligible for beef samples. Conversely, in an aqueous tuna extract, different %metMb values were obtained with the different equations. The discrepancy in the tuna sample results might be due to differences in absorption spectra for horse and tuna Mb. Therefore, a new set of equations derived from the absorption spectra of bigeye tuna Mb, reported by Matsuura and Hashimoto (1955), was established. The accuracy of the proposed equations was compared with the cyanmetmyoglobin (cyanmetMb) method. The results show that the total Mb concentrations estimated by our proposed equations were in good agreement with the results obtained by the conventional cyanmetMb method (R(2)=0.984). Therefore, the new set of proposed equations is valid for the spectrophotometric determination of the relative proportions of Mb derivatives and total Mb concentration in aqueous tuna meat extracts.

Supercooling and vitrification of aqueous glycerol solutions at normal and high pressures

The supercooling and vitrification of aqueous glycerol solutions was studied at high pressures. Homogeneous ice nucleation temperatures (T(H)) were obtained for aqueous glycerol solutions of R=50, 30, 20, 12, and 10 (R: moles of water/moles of glycerol) up to 300MPa. The R=20 glycerol solution formed a glass above 200MPa at a cooling rate of 200°C/min, indicating that pressure enhances glass-formation of aqueous glycerol solutions. The (dT(g)/dP) values were obtained for vitrified aqueous glycerol solutions of R=3, 5, 10, and 20. These data can be used for the development of cryo-preservation liquids for living cells at high pressures.

Characteristics and oil absorption in deep-fat fried batter prepared from ball-milled wheat flour.

BACKGROUND The porous structure generated during frying influences oil absorption and textural qualities. The alteration in physical properties of wheat flour is suspected to affect the structure formation. The present study investigated the effect of physicochemical changes in wheat flour by the ball-milling process on structure formation and consequently oil absorption of a fried wheat flour batter model. RESULTS Batter models containing 600 g kg(-1) moisture were made of 0-10 h ball-milled wheat flour and then fried in frying oil at 150 degrees C for 1-7 min. The samples made of milled flour possess larger pores and exhibit lower oil absorption than sample made of 0 h milled flour. The fracture force of a fried sample prepared from 5 and 10 h milled flour is lower than that of a sample prepared from 0 h milled flour. CONCLUSION The decrease in glass transition temperature (T(g)) and melting temperature (T(m)) of milled flour affect the microstructure formation in the fried wheat flour batter. The microstructure is responsible for oil absorption and fracturability in fried food. The samples made of flour of longer ball-milling time have lower oil absorption and higher crispness. Ball-milling may be a tool to produce mechanically modified wheat flour which can reduce oil absorption for fried batter.

Supercooling of aqueous dimethylsulfoxide solution at normal and high pressures: Evidence for the coexistence of phase-separated aqueous dimethylsulfoxide solutions of different water structures

Supercooling behavior of aqueous dimethylsulfoxide (DMSO) solution was investigated as a function of DMSO concentration and at high pressures. A linear relationship was observed for T(H) (homogeneous ice nucleation temperature) and T(m) (melting temperature) for the supercooling of aqueous DMSO solution at normal pressure. Analysis of the DTA (differential thermal analysis) traces for homogeneous ice crystallization in the bottom region of the T(H) curve for a DMSO solution of R=20 (R: moles of water/moles of DMSO) at high pressures supported the contention that the second critical point (SCP) of liquid water should exist at P(c2)= approximately 200 MPa and at T(c2)<-100 degrees C (P(c2): pressure of SCP, T(c2): temperature of SCP). The presence of two T(H) peaks for DMSO solutions (R=15, 12, and 10) suggests that phase separation occurs in aqueous DMSO solution (R<or=15) at high pressures and low temperatures (<-90 degrees C). The pressure dependence of the two T(H) curves for DMSO solutions of R=10 and 12 indicates that the two phase-separated components in the DMSO solution of R=10 have different liquid water structures [LDL-like and HDL-like structures (LDL: low-density liquid water, HDL: high-density liquid water)] in the pressure range of 120-230 MPa.

Prediction Approach to the Glass Transition Temperature of Amorphous Carbohydrate Polymer

Most of carbohydrate polymers exist, at least partially, in an amorphous state, and thus, glass transition occur during dehydration/rehydration and cooling/heating processing. Since various physical properties are changed drastically by the glass transition (Levine and Slade 1988; Roos 1995; Le Meste et al. 2002), it is important to understand the glass transition temperature (Tg).

Solubilities in the Ternary System Alkali Metal Halide–Glucose–Water

The solubility of glucose was measured in aqueous saturated alkali metal halide (NaF, NaCl, NaBr, NaI, KCl, KBr, and KI) solutions at 30°C. The solubility of glucose in saturated sodium halide solutions is lower than that in water. On the contrary, the solubility of glucose in saturated potassium halide solutions is higher than that in water. The determinations of glucose solubility were also carried out in some unsaturated NaCl or KCl solutions at 30°C. In the case of NaCl, the glucose solubility curve is not simple. It increases slightly at lower NaCl concentrations then decreases gradually with increases NaCl concentration. In the case of KCl, the curve is simple, the solubility of glucose increasing with increases KCl concentration. The determinations of alkali metal chloride solubilities were also carried out in the presence of glucose at 30°C.

Effects of fatty acid and emulsifier on the complex formation and in vitro digestibility of gelatinized potato starch

ABSTRACT The effects of fatty acid, monoacylglycerol, and polyglycerol fatty acid ester with varying chain length in their acyl chains on the extent of complex formation (complex index) and in vitro enzymatic digestibility of gelatinized potato starch were investigated. The complex index increased with increase in the concentration of the ligands (fatty acid, monoacylglycerol, and polyglycerol fatty acid ester), with the plateau in the complex index value depending on the type of ligands. In comparison of complex index among fatty acid-samples, the complex index maximum increased as the chain length increased up to octanoic acid and then decreased. In comparison of complex index among fatty acid-, monoacylglycerol-, and polyglycerol fatty acid ester-samples at each acyl chain, the complex index maximum followed the order polyglycerol fatty acid ester > monoacylglycerol > fatty acid. Fatty acid, monoacylglycerol, and polyglycerol fatty acid ester with long acyl chains greatly reduced the enzymatic hydrolysis of starch. Polyglycerol fatty acid ester with palmitic acid chains was the strongest inhibitor of starch hydrolysis, suggesting that further complex formation may occur during the hydrolysis of gelatinized starch (enzyme-annealing).

Effect of Emulsifier on Complex Formation and In Vitro Digestibility of Gelatinized Potato Starch

It is known that amylose and lipid compounds form a helical inclusion complex in gelatinized starch. The complex formation has attracted much attention because of impact on retrogradation (Tufvesson et al. 2001), in vivo (Holm et al. 1983) and in vitro (Guraya et al. 1997; Crowe et al. 2000) digestibility, and rheological properties (Kaur and Singh 2000; Gelders et al. 2006) of gelatinized starch.