Teepakorn Kongraksawech

Effect of Grain Protein Concentration on Falling Number of Ungerminated Soft White Winter Wheat

ABSTRACT Falling number (FN) values below 300 sec in the apparent absence of preharvest sprouting are periodically observed in the U.S. Pacific Northwest (USPNW). Wheat in the USPNW is predominantly soft-grained and often grown under conditions conducive to low grain protein concentration (GPC). Our hypothesis is that low GPC per se could be responsible for some low FN results and not elevated α-amylase from either sprouting or late-maturity amylase. The relationship between FN and GPC was investigated using grain from the 2011 wheat harvest. Soft white winter wheat samples from six locations in Oregon were tested in duplicate. Across the entire sample set, FN and GPC were positively correlated (r = 0.65, P ≤ 0.001). When putatively sprouted samples (FN < 280 sec) were removed from the analysis, the correlation was still apparent (r = 0.69, P ≤ 0.001). Hardness index was also correlated with FN (r = 0.45, P ≤ 0.001). Our preliminary conclusion is that GPC can be a substantial modulator of FN in the putati...

IONIC STRENGTH AND pH EFFECTS ON OPTICAL THERMOGRAPHS FOR BOVINE SERUM ALBUMIN (BSA) EFECTOS DE LA FUERZA IÓNICA Y EL pH SOBRE LOS TERMOGRAMAS ÓPTICOS DE LA SEROALBUMINA BOVINA (BSA)

Abstract An optical method using a custom-built system was investigated to study heating effects on bovine serum albumin (BSA) as affected by pH and ionic strength (IS). Changes in the optical rotation (OR) and transmitted light (TL) of BSA in 0.01 M phosphate buffer at pH 6.1, 7, and 7.9 with IS maintained at 0.04, 0.08, and 0.16 were monitored while heating the solution at ∼6°C/min from room temperature to ∼85°C. There was no significant effect of IS on BSAs denaturation temperature (Td) values. Td was affected by pH with lower values observed at pH 7.9 than at pH 7 but not statistically different from values at pH 6.1. Values at pH 6.1 and 7 were not significantly different either. These observations were consistent with literature values determined by differential scanning calorimetry. Changes in the TL signal, reflecting the formation of an opaque gel, were not detected at pH 7.9, identified only at the two highest IS at pH 7, and observed always at pH 6.1, i.e., closest to the pH value for the isoelectric point (pI) of BSA reported to be around pH 4.7 to 5.2. Promoting of gel formation by IS was attributed to the screening of intra- and intermolecular electrostatic forces. Resumen Un método óptico basado en un sistema experimental especialmente construido para este propósito fue usado para investigar la influencia del pH y la fuerza iónica sobre los efectos térmicos en la seroalbúmina bovina (BSA). Los cambios en la rotación óptica (OR) y la luz transmitida (TL) de soluciones buffer de fosfato 0,01 M con 2,5% de seroalbúmina bovina (BSA) a pH 6,1, 7 y 7,9 y una fuerza iónica (IS) de 0,04, 0,08 ó 0,16 fueron monitoreados durante su calentamiento a ∼6°C/min desde temperatura ambiente hasta ∼85°C. No se observó un efecto estadísticamente significativo de IS sobre la temperatura de desnaturalizacion térmica (Td). Td fue afectada por el pH con valores menores observados a pH 7,9 que a pH 7 pero no estadísticamente diferentes del valor a pH 6,1. Valores a pH 6,1 y 7 tampoco fueron estadísticamente diferentes entre ellos. Estas observaciones son consistentes con valores reportados en la literatura y obtenidos por el método de Calorimetría Diferencial de Barrido (DSC). Cambios en la señal de TL, reflejando la formación de un gel opaco, no fueron detectados a pH 7,9, encontrados solo a los valores mayores de IS a pH 7, y observados consistentemente a pH 6,1, el valor de pH incluido en este estudio más cercano al punto isoeléctrico de BSA y reportado entre pH 4,7 y 5,2. El efecto de la IS en la mayor formación de geles fue atribuido al su capacidad de bloquear fuerzas electrostáticas intra- e intermoleculares. Palabras clave: Propiedades ópticas, seroalbúmina bovina, luz transmitida

Laser metrology in food-related systems

An optical system was developed using a low-cost semiconductor laser and commercial optical and electronic components, to monitor food processes by measuring changes in optical rotation (OR) of chiral compounds. The OR signal as a function of processing time and sample temperature were collected and recorded using a computer data acquisition system. System has been tested during two different processes: sugar-protein interaction and, beer fermentation process. To study sugar-protein interaction, the following sugars were used: sorbitol, trehalose and sucrose, and in the place of Protein, Serum Albumin Bovine (BSA, A-7906 Sigma-Aldrich). In some food processes, different sugars are added to protect damage of proteins during their processing, storage and/or distribution. Different sugar/protein solutions were prepared and heated above critical temperature of protein denaturation. OR measurements were performed during heating process and effect of different sugars in protein denaturation was measured. Higher sensitivity of these measurements was found compared with Differential Scanning Calorimetry, which needs higher protein concentration to study these interactions. The brewing fermentation process was monitored in-situ using this OR system and validated by correlation with specific density measurements and gas chromatography. This instrument can be implemented to monitor fermentation on-line, thereby determining end of process and optimizing process conditions in an industrial setting. The high sensitivity of developed OR system has no mobile parts and is more flexible than commercial polarimeters providing the capability of implementation in harsh environments, signifying the potential of this method as an in-line technique for quality control in food processing and for experimentation with optically active solutions.

Measuring Oxidative Gelation of Aqueous Flour Suspensions Using the Rapid Visco Analyzer

ABSTRACT The Rapid Visco Analyzer (RVA) was investigated as a tool to measure oxidative gelation capacity (OGC) of aqueous wheat flour suspensions. One club wheat patent flour was used to determine optimal hydration time, and 33 straight-grade flours (representing 12 hard and 21 soft varieties) were used to observe varietal differences in OGC. A 33.3% w/w flour–water suspension was tested in the RVA at 30°C and 160 rpm for 1 min to establish the flour–water baseline viscosity, and then 65 μL of 3% H2O2 was added and the viscosity of the suspension measured at 160 rpm for a further 5 min. Flour from the club wheat showed that 20 min of prehydration was needed to observe full OGC potential. For the 33 straight-grade flours, final RVA water baseline viscosity was correlated with Bostwick Consistometer (BC) flow (r = −0.93, P ≤ 0.01), and RVA H2O2 peak viscosity was correlated with H2O2 BC flow (r = –0.81, P ≤ 0.01). The RVA was able to differentiate H2O2-reactive from nonreactive flours. The RVA can observe ...

Unexpectedly Good Soft Wheat Quality from a Hard × Soft Cross

ABSTRACT The soft-grained progeny of a recombinant inbred line (RIL) population was characterized for a comprehensive set of quality traits and associated quantitative trait loci (QTLs). The population was derived from the cross Tubbs (soft grained) × NSA 98-0995 (hard grained) and was grown in two crop years in Corvallis, Oregon. Transgressive segregation was observed for all of the studied traits. Hardness index was significantly correlated with several important traits related to the absorption capacity of the flour for diagnostic aqueous solvents. Five lines with a desired combination of superior soft wheat quality traits were also identified. Fifteen QTLs were detected on nine wheat chromosomes for eight traits. The observed transgressive segregation was useful, because RILs with potentially above average soft wheat quality were unexpectedly identified in this hard × soft cross. The QTLs identified in this study could be useful in marker-assisted selection for future preselection of progeny from Tubb...