Study of Thermal Properties of Oat Globulin by Differential Scanning Calorimetry

Abstract

The thermal behavior of oat globulin was studied by differential scanning calorimetry (DSC). The effects of pH, salts, and of various structure perturbants upon thermal characteristics were determined. Raising or lowering pH from near neutrality reduced denaturation temperature. (TJ, enthalpy (AH) and coopcrativity indicated by increase in width at half height (AT&.The effect of salts on thermal stability was related to their position in the lyotrophic series and suggests involvement of hydrophobic interaction in the thermal stability of oat globulin. Increasing concentrations of urea progressively lowered Td and AH and increased ATI,~; sodium dodecyl sulfate (SDS) lowered AH without affecting Td; ethylene glycol (EC) lowered Td without changing AH. Dithiothreitol did not affect DSC characteristics suggesting that disulfide bonds do not contribute to the thermal response of oat globulin.

Effects of transglutaminase treatment on the thermal properties of soy protein isolates

“…At more than 6 M of urea, the endothermic peak of glycinin of native SPI was nearly not discernible, indicating extensive protein denaturation. Similar eVects of urea on the H were observed in the oat globulins (Harwalkar & Ma, 1987), red bean globulins (Phaseolus angularis; Meng & Ma, 2001) and buckwheat proteins (unpublished results). In the P-SPI cases, interestingly, there were no signiWcant changes of H in the interval 0-6 M urea (Fig.…”

Thermal properties of buckwheat proteins as related to their lipid contents

“…Urea effectively disrupts the hydrogen bonding, and facilitates protein unfolding by weakening the hydrophobic interactions (Kinsella, 1982). Urea also increases the 'permitivity' of water for the apolar residues causing loss of protein ordered structure and thermal stability (Harwalkar & Ma, 1987). Thus, the conformation or molecular stability of buckwheat proteins (especially 13S globulins) may be mainly maintained by hydrogen bonding and hydrophobic interactions, and the role of disulfide bonds in thermal response by DSC is insignificant or negligible, since the disulfide bonds are not expected to be cleaved by 8 M urea.…”

“…Using the DSC analysis technique, the thermal denaturation of some food proteins, such as muscle proteins (Paredi, Tomas, & Crupkin, 2002), egg albumin (Donovan, Mapes, Davis, & Garbaldi, 1975), soybean proteins (Scilingo & Añ ó n, 1996), a-lactalbumin and b-lactoglobulin (Boye & Alli, 2000), fababean proteins (Arntfield, Murray, & Ismond, 1986), oat globulins (Harwalkar & Ma, 1987;Ma & Harwalkar, 1988), red bean globulins (Meng & Ma, 2001) and flaxseed proteins (Li-Chan & Ma, 2002) has been widely studied. In these studies, most of protein samples used were usually purified or partially purified, and the influence of other components (e.g., lipid content) on their thermal properties was not evaluated.…”

Application of differential scanning calorimetry in food research and food quality assurance

“…Maximum stability is observed generally between pH 5 and 8 while extremes ofpH, in either the acid or alkaline region resulted in decreased denaturation temperatures and apparently smaller endotherms [21,22]. The thermal stability of myosin filaments showed remarkable sensitivities to changes ofpH and ionic strength [23,24].…”

“…Thermal stability of several proteins of interest to the food industry were investigated indeed by DSC as affected by various environmental factors. Studies on egg proteins such as ovalbumin [8,9], conalbumin [10] and lyzozyme [11], milk proteins such as beta-lactoglobulin [12][13][14], ot-lactalbumin [15,16] and casein, as well as muscle proteins such as myosin and actin [17,18] and plant proteins such as vicilin from faba beans [8] and rapeseed storage protein [19], and globulins isolated from various cereal grains [20] can be mentioned.…”