Steven W. Lloyd

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.

Fungal Infections of Fresh-Cut Fruit Can Be Detected by the Gas Chromatography–Mass Spectrometric Identification of Microbial Volatile Organic Compounds

There is a large and rapidly growing market for fresh-cut fruit. Microbial volatile organic compounds indicate the presence of fungal or bacterial contamination in fruit. In order to determine whether microbial volatile organic compounds can be used to detect contamination before fruit becomes unmarketable, pieces of cantaloupe, apple, pineapple, and orange were inoculated with a variety of fungal species, incubated at 25 degrees C, then sealed in glass vials. The volatiles were extracted by headspace solid-phase microextraction and analyzed by gas chromatography-mass spectrometry. Forty-five compounds were identified that might serve as unique identifiers of fungal contamination. Fungal contamination can be detected as early as 24 h after inoculation.

Flavor of Fresh Blueberry Juice and the Comparison to Amount of Sugars, Acids, Anthocyanidins, and Physicochemical Measurements

Six cultivars of southern highbush (SHB) and rabbiteye (RE) blueberry samples were harvested on 2 different dates. Each treatment combination was pressed 2 times for repeated measures. Fresh juice was characterized for 18 flavor/taste/feeling factor attributes by a descriptive flavor panel. Each sample was measured for sugars, acids, anthocyanidins, Folin-Ciocalteu, soluble solids (BRIX), titratable acidity (TA), and antioxidant capacity (ORACFL ). Flavors were correlated with the composition and physicochemical data. Blueberry flavor correlated with 3 parameters, and negatively correlated with 2. Strawberry correlated with oxalic acid and negatively correlated with sucrose and quinic acid. Sweet aroma correlated with oxalic and citric acid, but negatively correlated with sucrose, quinic, and total acids. Sweet taste correlated with 11 parameters, including the anthocyanidins; and negatively correlated with 3 parameters. Neither bitter nor astringent correlated with any of the antioxidant parameters, but both correlated with total acids. Sour correlated with total acids and TA, while negatively correlating with pH and BRIX:TA. Throat burn correlated with total acids and TA. Principal component analysis negatively related blueberry, sweet aroma, and sweet to sour, bitter, astringent, tongue tingle, and tongue numbness. The information in this component was related to pH, TA, and BRIX:TA ratio. Another principal component related the nonblueberry fruit flavors to BRIX. This PC, also divided the SHB berries from the RE. This work shows that the impact of juice composition on flavor is very complicated and that estimating flavor with physicochemical parameters is complicated by the composition of the juice.

Screening for Sensory Quality in Foods Using Solid Phase Micro-Extraction Tandem Mass Spectrometry

Tandem mass spectrometry has proven a useful technique for the elucidation of chemical structures. However, there are no applications of tandem mass spectrometry for routine applications. This is in part due to the limitation of samples being introduced into the ion source in the presence of a solvent. The relative large amount of solvent molecules overwhelms the presence of the analyte and the signal, if any, is lost in the chemical noise. With the introduction of solid phase microextraction (SPME), the analyte can now be placed in the mass spectrometric source in a solvent free environment (Belardi and Pawliszyn, 1989; Eisert and Levsen, 1996; Kataoka et al., 2000). The major contributors to the muddy/musty off-flavor in drinking water systems are 2- methylisoborneol (2-MIB) and geosmin (Lovell, 1983). These compounds are generally placed in the water column by blue-green algae, but are also produced by bacteria and fungi. Associated with algae blooms in late summer, the compounds are perceptible to the human nose at the low parts per trillion range (Persson, 1980). They plague drinking water systems and are particularly problematic in the warm water aquaculture production of farm-raised catfish. The current method for analysis of 2-MIB and geosmin is closed loop stripping (McGuire et al., 1981) and purge and trap (Johnsen and Lloyd, 1992) with GC/MS analysis. However, a technique employing SPME-GC/MS has recently been reported for the analysis of these compounds at the parts per trillion level (Lloyd et al., 1998; Watson et al., 2000). The SPME technique has proven to be an excellent method for the concentration of volatile compounds, and in combination with gas chromatography for separation and mass spectrometry for detection, provides a state-of- the-art analytical tool.

Chemical and nutritional properties of channel and hybrid catfish byproducts

Abstract The objective of this study was to chemically characterize both channel and hybrid catfish parts including heads, frames, viscera, skin, and fillet trimming mince. Triplicate samples of channel and hybrid catfish byproduct parts were obtained from a large commercial catfish processor and analyzed for percent moisture, lipid, protein, ash, and amino acid and fatty acid profiles were determined. The content of the off‐flavor compounds, 2‐methylisoborneol (MIB) and geosmin were also determined. The lipid content of samples were 13.6% and 10.0% for channel and hybrid skins, 17.7% and 21.4% for channel and hybrid viscera, 20.0% and 19.1% for channel and hybrid frames, and 9.7% and 9.3% for channel and hybrid heads. The protein content of samples ranged from a high of 22.8% for channel catfish skins, to a low of 13.4% for channel frames. Low levels of geosmin, <1 ppb, were detected in the byproduct samples, while no MIB was detected. Palmitic, oleic, and linoleic acid comprised approximately 80% of the fatty acids in the byproduct tissues. The amino acid profiles indicated that the catfish mince had high levels of lysine and methionine and other essential amino acids. Results from this study will be used in the development of new value‐added products from catfish byproducts.

Improving the Analysis of Anthocyanidins from Blueberries Using Response Surface Methodology

Received: April 11, 2016 Revised: August 5, 2016 Accepted: August 9, 2016 Abstract: Background: Recent interest in the health promoting potential of anthocyanins points to the need for robust and reliable analytical methods. It is essential to know that the health promoting chemicals are present in juices and other products processed from whole fruit. Many different methods have been published using a wide variety of conditions for the hydrolysis of anthocyanins to anthocyanidins.