Casey C. Grimm

Rapid gas chromatographic technique for quantifying 2-acetyl-1-pyrroline and hexanal in rice (Oryza sativa, L.).

ABSTRACT The aroma of rice plays a role in its consumer acceptability. The popcorn-like smell of aromatic rice stemming primarily from its 2- acetyl-1-pyrroline (2-AP) content is considered desirable by many consumers. Conversely, hexanal has been correlated with off odors in rice that develop from lipid oxidation. A rapid method for 2-AP and hexanal quantification suitable for use in breeding programs, large-scale research efforts, and quality assurance programs is needed. While developing such a method, sample preparation (degree of milling, particle size), solvent extraction time and temperature, and gas chromatographic parameters were studied. Particle size had no influence on 2-AP or hexanal recovered. One extraction solubilized ≈80% of the 2-AP and 56% of the hexanal present in milled rice. The optimum extraction method was assessed to require 0.3 g of ground brown or milled rice in methylene chloride held at 85°C for 2.5 hr. The complete gas chromatographic run requires ≈25 min, and 50 samples can ...

Important Sensory Properties Differentiating Premium Rice Varieties

In rice-consuming countries, specific varieties are recognized as premium, “gold standard” varieties, while others are recognized as being superior but second best, despite being identical using the current suite of tools to evaluate quality. The objectives of this study were to determine if there are distinguishable differences in sensory properties of premium and second best varieties and whether these differences are common to premium varieties. Color, an important sensory property, was determined on the raw and cooked rice using a colorimeter. As raw rice, some of the premium varieties were whiter than their second best counterparts while others were not. However, when cooked, with two exceptions, the premium varieties were of the same or greater whiteness than their counterparts. A trained sensory panel employed descriptive sensory analysis, an objective tool, to characterize and analytically measure the flavor (aromatics, taste, mouthfeel) and texture of premium and second best varieties collected from nine rice-consuming countries. Sweet taste, popcorn aroma/flavor, and water-like metallic mouthfeel showed significant differences in intensity between the premium–second best variety pairs. Slickness, roughness, and springiness were the major traits that distinguished the texture of varieties. Quality evaluation programs do not routinely measure these texture and flavor traits, but the fact that they distinguished the varieties in most pairs indicates that their measurement should be added to the suite of grain quality tests in the development of new higher-yielding, stress-tolerant varieties. The incorporation of premium quality will ensure that quality is no impediment to widespread adoption leading to enhanced productivity and food security.

Effects of Organic Fertility Management on Physicochemical Properties and Sensory Quality of Diverse Rice Cultivars

ABSTRACT The demand for organically grown rice has increased with consumer demand for organic foods. The objective of this research was to determine whether there are physicochemical differences in organically and conventionally grown rice that contribute to flavor and texture differences, as determined by descriptive sensory analysis, an objective tool. Five diverse cultivars (four nonwaxy and one waxy) were grown at Beaumont, TX, with 100 or 50% recommended nitrogen fertilizer using conventional management or with chicken litter using organic management. Mean protein content differed significantly (P < 0.05) with fertilizer input, whereas mean apparent amylose and mineral contents (with few exceptions) did not differ. The mean protein content of each cultivar grown with the 100% N rate typically used was significantly higher (P < 0.05) than that of the cultivar grown organically or at the 50% N rate. The mean protein contents of the cultivars grown organically and at the 50% N rate did not significantly...

Effects of drain and harvest dates on rice sensory and physicochemical properties

ABSTRACT Timing of field draining and harvesting of rice with meteorological conditions can allow growers to foster conditions for high head rice yield (HRY). The effects of timing of draining and harvesting on rice sensory and physicochemical properties are not well understood. The objective of this study was to determine the effects of varying drain and harvest dates on the sensory and physicochemical properties of M-202 grown in California under controlled field conditions. Drain date had a significant (P 0.05) differences in texture were measured as a result of these parameters being low. Drain date did not affect the volatile composition or flavor of the rice. Harvest date had no effect (P > 0.05) on amylose content and a sig...

Near-Infrared Reflectance Analysis for Prediction of Cooked Rice Texture

ABSTRACT The ability of near-infrared (NIR) spectroscopy to predict sensory texture attributes of diverse rice cultivars was examined. The sensory texture of 87 samples representing 77 different short-, medium-, and long-grain cultivars was evaluated by trained panelists using descriptive analysis. Correlations between sensory texture attributes and NIR reflectance data were examined using the multivariate method of partial least squares (PLS) regression. Texture attributes (hardness, initial starchy coating, cohesiveness of mass, slickness, and stickiness) measured by panelists in the early evaluation phases were successfully predicted (R2calibration 0.71–0.96). Cohesiveness of mass, the maximum degree to which the sample holds together in a mass while chewing, was best modeled with R2calibration = 0.96 and R2validation = 0.90. Key wavelengths contributing to the models describing the texture attributes were wavelengths also contributing to models for amylose, protein, and lipid contents.

Formation and occurrence of flavor components in Noble muscadine wine

Flavor development in Noble muscadine wine during fermentation and aging was determined with a combined gas chromatograph-mass spectrometer. The source of 2-phenylethanol, a major aroma component of the wine, is predominantly through biosynthesis during the vinification process, although the alcohol was also found to be present in fresh muscadine grape skin. The involvement of substituted benzene derivatives in the formation of phenyl ethanol during fermentation and aging of wines is proposed. The complexity of the volatile aroma extracts increased with time, especially after fermentable sugars were exhausted. Anaerobic formation of fatty acid esters also commenced after active fermentation had ceased. These compounds constitute major components of the aged muscadine wine. Effluent sniffing indicated that many odorous compounds including phenyl ethanol and methyl succinate contribute significantly to the muscadine wine aroma.

The role of Aspergillus flavus veA in the production of extracellular proteins during growth on starch substrates

The aflatoxin-producer and opportunistic plant pathogenic, filamentous fungus Aspergillus flavus is responsible for the contamination of corn and other important agricultural commodities. In order to obtain nutrients from the host A. flavus produces a variety of extracellular hydrolytic enzymes. Interestingly, A. flavus amylase and protease activity are dependent on the global regulator veA, a gene known to regulate morphogenesis and secondary metabolism in numerous fungi. Analysis of starch degradation by fungal enzymes secreted into broths of starch- or corn kernel-based media showed a notable accumulation of glucose in samples of the A. flavus control strain while the deletion veA sample accumulated high levels of maltose and maltotriose and only a small amount of glucose. Furthermore, SDS-PAGE and proteomics analysis of culture broths from starch- or corn kernel-based media demonstrated differential production of a number of proteins that included a reduction in the amount of a glucoamylase protein in the veA mutant compared to the control strain, while an alpha-amylase was produced in greater quantities in the veA mutant. Quantitative real-time PCR and western blot analyses using anti-glucoamylase or alpha-amylase antisera supported the proteomics results. Additionally, an overall reduction in protease activity was observed in the veA mutant including production of the alkaline protease, oryzin, compared to the control strain. These findings contribute to our knowledge of mechanisms controlling production of hydrolases and other extracellular proteins during growth of A. flavus on natural starch-based substrates.

Analysis of 2-Acetyl-1-Pyrroline in Rice by HSSE/GC/MS

ABSTRACT An extremely sensitive method for the analysis of 2-acetyl-1-pyrroline (2AP) in rice, employing stir bar sorptive extraction (Twister) was studied. The Twister stir bar is placed in the headspace of a 20-mL vial containing 1 g of rice kernels, 7.5 mL of 0.1M KOH, and 2.2 g of NaCl, along with a second Teflon-coated stir bar for mixing. Analytes are adsorbed onto the Twister for 4 hr at 40°C and then desorbed at 270°C into a GC column while cryofocusing at –80°C. The headspace sorptive extraction (HSSE) method was able to detect 10%) was not as good as the GC/FID method (≈6%). Using HSSE, 2AP was observed in all samples generally considered to be aromatic and was not observed in any nonaromatic samples. Additionally, a modified method for the synthesis of 2-acetyl-1-pyrroline was studied and the presence of a tautomer of 2-acetyl-1-pyrroline was confirmed.

Decreased immunoglobulin E (IgE) binding to cashew allergens following sodium sulfite treatment and heating.

Cashew nut and other nut allergies can result in serious and sometimes life-threatening reactions. Linear and conformational epitopes within food allergens are important for immunoglobulin E (IgE) binding. Methods that disrupt allergen structure can lower IgE binding and lessen the likelihood of food allergy reactions. Previous structural and biochemical data have indicated that 2S albumins from tree nuts and peanuts are potent allergens, and that their structures are sensitive to strong reducing agents such as dithiothreitol. This study demonstrates that the generally regarded as safe (GRAS) compound sodium sulfite effectively disrupted the structure of the cashew 2S albumin, Ana o 3, in a temperature-dependent manner. This study also showed that sulfite is effective at disrupting the disulfide bond within the cashew legumin, Ana o 2. Immunoblotting and ELISA demonstrated that the binding of cashew proteins by rabbit IgG or IgE from cashew-allergic patients was markedly lowered following treatment with sodium sulfite and heating. The results indicate that incorporation of sodium sulfite, or other food grade reagents with similar redox potential, may be useful processing methods to lower or eliminate IgE binding to food allergens.

Heat-induced alterations in cashew allergen solubility and IgE binding

Cashew nuts are an increasingly common cause of food allergy. We compare the soluble protein profile of cashew nuts following heating. SDS-PAGE indicate that heating can alter the solubility of cashew nut proteins. The 11S legumin, Ana o 2, dominates the soluble protein content in ready to eat and mildly heated cashew nuts. However, we found that in dark-roasted cashew nuts, the soluble protein profile shifts and the 2S albumin Ana o 3 composes up to 40% of the soluble protein. Analysis of trypsin-treated extracts by LC/MS/MS indicate changes in the relative number and intensity of peptides. The relative cumulative intensity of the 5 most commonly observed Ana o 1 and 2 peptides are altered by heating, while those of the 5 most commonly observed Ana o 3 peptides remaine relatively constant. ELISA experiments indicate that there is a decrease in rabbit IgG and human serum IgE binding to soluble cashew proteins following heating. Our findings indicate that heating can alter the solubility of cashew allergens, resulting in altered IgE binding. Our results support the use of both Ana o 2 and Ana o 3 as potential cashew allergen diagnostic targets.