Detection of Profenofos in Chinese Kale, Cabbage, and Chili Spur Pepper Using Fourier Transform Near-Infrared and Fourier Transform Mid-Infrared Spectroscopies.

Different types of quantitative technology based on infrared spectroscopy to detect profenofos were compared based on Fourier transform near-infrared (FT-NIR; 12,500-4000 cm-1) and Fourier transform mid-infrared (FT-MIR; 4000-400 cm-1) spectroscopies. Standard solutions in the range of 0.1-100 mg/L combined with the dry-extract system for infrared (DESIR) technique were analyzed. Based on partial least-squares regression (PLSR) to develop a calibration equation, FT-NIR-PLSR produced the best prediction of profenofos residues based on the values for R 2 (0.87), standard error of prediction or SEP (11.68 mg/L), root-mean-square error of prediction or RMSEP (11.50 mg/L), bias (-0.81 mg/L), and ratio performance to deviation or RPD (2.81). In addition, FT-MIR-PLSR produced the best prediction of profenofos residues based on the values for R 2 (0.83), SEP (13.10 mg/L), RMSEP (13.00 mg/L), bias (1.46 mg/L), and RPD (2.49). Based on the ease of use and appropriate sample preparation, FT-NIR-PLSR combined with DESIR was chosen to detect profenofos in Chinese kale, cabbage, and chili spur pepper at concentrations of 0.53-106.28 mg/kg. The quick, easy, cheap, effective, rugged, and safe technique coupled with gas chromatography-mass spectrometry was used to obtain the actual values. The best FT-NIR-PLSR equation provided good profenofos detection in all vegetables based on values for R 2 (0.88-0.97), SEP (5.27-11.07 mg/kg), RMSEP (5.25-11.00 mg/kg), bias (-1.39 to 1.30 mg/kg), and RPD (2.91-5.22). These statistics revealed no significant differences between the FT-NIR predicted values and actual values at a confidence interval of 95%, with agreeable results presented at pesticide residue levels over 30 mg/kg. FT-NIR spectroscopy combined with DESIR and PLSR should be considered as a promising screening method for pesticide detection in vegetables.

Ohmic Heating of an Electrically Conductive Food Package.

Ohmic heating through an electrically conductive food package is a new approach to heat the food and its package as a whole after packing to avoid post-process contamination and to serve consumer needs for convenience. This process has been successfully completed using polymer film integrated with an electrically conductive film to form a conductive package. Orange juice packed in the conductive package surrounded with a conductive medium was pasteurized in an ohmic heater. A mathematical model was developed to simulate the temperature distribution within the package and its surroundings. A 3-D thermal-electric model showed heating uniformity inside the food package while the hot zone appeared in the orange juice adjacent to the conductive film. The accuracy of the model was determined by comparing the experimental results with the simulated temperature and current drawn; the model showed good agreement between the actual and simulated results. An inoculated pack study using Escherichia coli O157:H7 indicated negative growth of viable microorganisms at the target and over target lethal process temperatures, whereas the microorganism was present in the under target temperature treatment. Consequently, our developed ohmic heating system with conductive packaging offers potential for producing safe food.

Effect of okra cell wall and polysaccharide on physical properties and stability of ice cream.

Stabilizers are used in ice cream to increase mix viscosity, promote smooth texture, and improve frozen stability. In this study, the effects of varying concentrations (0.00%, 0.15%, 0.30%, and 0.45%) of okra cell wall (OKW) and its corresponding water-soluble polysaccharide (OKP) on the physical characteristics of ice cream were determined. Ice cream mix viscosity was measured as well as overrun, meltdown, and consumer acceptability. Ice recrystallization was determined after ice cream was subjected to temperature cycling in the range of -10 to -20 °C for 10 cycles. Mix viscosity increased significantly as the concentrations of OKW and OKP increased. The addition of either OKW or OKP at 0.15% to 0.45% significantly improved the melting resistance of ice cream. OKW and OKP at 0.15% did not affect sensory perception score for flavor, texture, and overall liking of the ice cream. OKW and OKP (0.15%) reduced ice crystal growth to 107% and 87%, respectively, as compared to 132% for the control (0.00%). Thus, our results suggested the potential use of OKW and OKP at 0.15% as a stabilizer to control ice cream quality and retard ice recrystallization. OKP, however, at 0.15% exhibited greater effect on viscosity increase and on ice recrystallization inhibition than OKW.

Whey protein-okra polysaccharide fraction blend edible films: tensile properties, water vapor permeability and oxygen permeability.

BACKGROUND: A hot-buffer-soluble-solid fraction (HBSS) and an alkaline-soluble-solid fraction (ASS) of okra polysaccharides (OKP) were obtained using sequential extraction. These fractions were combined with whey protein isolate (WPI) and glycerol (Gly) plasticizer to form blend edible films. Effects of OKP fraction and content on tensile properties, water vapor permeability (WVP) and oxygen permeability (OP) were determined. RESULTS: HBSS film had significantly higher percent elongation (%E) and lower elastic modulus (EM), WVP and OP than ASS film. Increasing HBSS or ASS content in blend films with WPI significantly reduced film tensile strength and EM and increased film %E and WVP. OP values for WPI-HBSS blend films were significantly lower than OP for WPI or HBSS film. WPI-HBSS and WPI-ASS blend films had lower WVP and OP than WPI films with equivalent tensile properties. CONCLUSIONS: WPI-HBSS blend films have higher WVP and lower OP than WPI film or HBSS film, indicating unique interactions between WPI and HBSS. Compared to WPI film, WPI-HBSS blend films have improved flexibility, stretchability and oxygen barrier. Different HBSS and ASS compositions and structures are responsible for property differences between HBSS and ASS films and between WPI-HBSS and WPI-ASS blend films.

Use of average molecular weights for product categories to predict freezing characteristics of foods.

In the design of food freezing process, food property parameters, initial freezing temperature (T(Fi)), and frozen water fraction (X(I)) are required. The predictive approaches of these 2 parameters have been developed based on mass fractions and molecular weights of specific food components such as proteins, carbohydrates, minerals, and acids/bases. In this study, the molecular weights of the key mineral and acid/base components were successfully represented using average molecular weights (M) and 4 T(Fi) and X(I) calculation approaches were proposed. Based on an analysis of 212 food products, the absolute differences (AD) between the experimental and predicted T(Fi) values for the 4 approaches were small. The prediction for the food model category was excellent with average AD values as low as +/- 0.03 degrees C. For the other food categories, the prediction efficiency was impressive with values between +/- 0.22 and +/- 0.38 degrees C. The predicted relationship between temperature and X(I) for all analyzed food products provided close agreements with experimental data.

Okra pectin contains an unusual substitution of its rhamnosyl residues with acetyl and alpha-linked galactosyl groups.

The okra plant, Abelmoschus esculentus (L.) Moench, a native plant from Africa, is now cultivated in many other areas such as Asia, Africa, Middle East, and the southern states of the USA. Okra pods are used as vegetables and as traditional medicines. Sequential extraction showed that the Hot Buffer Soluble Solids (HBSS) extract of okra consists of highly branched rhamnogalacturonan (RG) I containing high levels of acetyl groups and short galactose side chains. In contrast, the CHelating agent Soluble Solids (CHSS) extract contained pectin with less RG I regions and slightly longer galactose side chains. Both pectic populations were incubated with homogeneous and well characterized rhamnogalacturonan hydrolase (RGH), endo-polygalacturonase (PG), and endo-galactanase (endo-Gal), monitoring both high and low molecular weight fragments. RGH is able to degrade saponified HBSS and, to some extent, also non-saponified HBSS, while PG and endo-Gal are hardly able to degrade either HBSS or saponified HBSS. In contrast, PG is successful in degrading CHSS, while RGH and endo-Gal are hardly able to degrade the CHSS structure. These results point to a much higher homogalacturonan (HG) ratio for CHSS when compared to HBSS. In addition, the CHSS contained slightly longer galactan side chains within its RG I region than HBSS. Matrix-assisted laser desorption ionization-time of flight mass spectrometry indicated the presence of acetylated RG oligomers in the HBSS and CHSS enzyme digests and electron spray ionization-ion trap-mass spectrum showed that not only galacturonosyl residues but also rhamnosyl residues in RG I oligomers were O-acetylated. NMR spectroscopy showed that all rhamnose residues in a 20kDa HBSS population were O-acetylated at position O-3. Surprisingly, the NMR data also showed that terminal alpha-linked galactosyl groups were present as neutral side chain substituents. Taken together, these results demonstrate that okra contained RG I structures which have not been reported before for pectic RG I.

Characterisation of cell wall polysaccharides from okra (Abelmoschus esculentus (L.) Moench).

Okra pods are commonly used in Asia as a vegetable, food ingredient, as well as a traditional medicine for many different purposes; for example, as diuretic agent, for treatment of dental diseases and to reduce/prevent gastric irritations. The healthy properties are suggested to originate from the high polysaccharide content of okra pods, resulting in a highly viscous solution with a slimy appearance when okra is extracted with water. In this study, we present a structural characterisation of all major cell wall polysaccharides originating from okra pods. The sequential extraction of okra cell wall material yielded fractions of soluble solids extractable using hot buffer (HBSS), chelating agent (CHSS), dilute alkaline (DASS) and concentrated alkaline (CASS). The HBSS fraction was shown to be rich in galactose, rhamnose and galacturonic acid in the ratio 1.3:1:1.3. The degree of acetylation is relatively high (DA=58) while the degree of methyl esterification is relatively low (DM=24). The CHSS fraction contained much higher levels of methyl esterified galacturonic acid residues (63% galacturonic acid; DM=48) in addition to minor amounts of rhamnose and galactose. The ratio of galactose to rhamnose to galacturonic acid was 1.3:1.0:1.3 and 4.5:1.0:1.2 for HBSS and CHSS, respectively. These results indicated that the HBSS and CHSS fractions contain rhamnogalacturonan type I next to homogalacturonan, while the latter is more prevailing in CHSS. Also the DASS fraction is characterised by high amounts of rhamnose, galactose, galacturonic acid and some arabinose, indicating that rhamnogalacturonan I elements with longer arabinose- and galactose-rich side chains were part of this fraction. Partial digestion of HBSS and CHSS by pectin methyl esterase and polygalacturonase resulted in a fraction with a lower Mw and lower viscosity in solution. These samples were subjected to NMR analysis, which indicated that, in contrast to known RG I structure, the acetyl groups in HBSS are not located on the galacturonic acid residues, while for CHSS only part of the acetyl groups are located on the RG I galacturonic acid residues. The CASS fraction consisted of XXXG-type xyloglucan and 4-methylglucuronoxylan as shown by their sugar (linkage) composition and enzymatic digestion.