| 1. |
- Anker, M., et al.
(författare)
-
Effects of pH and the gel state on the mechanical properties, moisture contents, and glass transition temperatures of whey protein films
- 1999
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 47:5, s. 1878-1886
-
Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties, moisture contents (MC), and glass transition temperature (T(g)) of whey protein isolate (WPI) films were studied at various pH values using sorbitol (S) as a plasticizer. The films were cast from heated aqueous solutions and dried in a climate chamber at 23 °C and 50% relative humidity (RH) for 16 h. The critical gel concentrations (c(g)) for the cooled aqueous solutions were found to be 11.7, 12.1, and 11.3% (w/w) WPI for pH 7, 8, and 9, respectively. The cooling rate influenced the c(g), in that a lower amount of WPI was needed for gelation when a slower cooling rate was applied. Both cooling rates used in this study showed a maximum in the c(g) at pH 8. The influence of the polymer network on the film properties was elucidated by varying the concentration of WPI over and under the c(g). Strain at break (?(b)) showed a maximum at the c(g) for all pH values, thus implying that the most favorable structure regarding the ability of the films to stretch is formed at this concentration. Young's modulus (E) and stress at break (?(b)) showed a maximum at c(g) for pH 7 and 8. The MC and ?(b) increased when pH increased from 7 to 9, whereas T(g) decreased. Hence, T(g) values were -17, -18, and -21 °C for pH 7, 8, and 9, respectively. E and ?(b) decreased and ?(b) and thickness increased when the surrounding RH increased. The thickness of the WPI films also increased with the concentration of WPI.
|
|
| 2. |
- Anker, M., et al.
(författare)
-
Mechanical Properties, Water Vapor Permeability, and Moisture Contents of ?-Lactoglobulin and Whey Protein Films Using Multivariate Analysis
- 1998
-
Ingår i: Journal of Agricultural and Food Chemistry. - 0021-8561 .- 1520-5118. ; 46:5, s. 1820-1829
-
Tidskriftsartikel (refereegranskat)abstract
- Mechanical and barrier properties of ?-lactoglobulin (?-Lg) and whey protein isolate (WPI) films were studied using sorbitol (S) as a plasticizer. The films were cast from heated aqueous solutions and dried in a climate chamber at 23 °C and 50% relative humidity for 16 h. The multivariate analysis used has proved to be a valuable tool for evaluating and quantifying the influences of the variables in the specified experimental domain. Two identical factorial designs were applied to evaluate the influence of the concentration of ?-Lg and WPI, the concentration of S, and the pH. The two materials, ?-Lg and WPI, show similar results, which can be attributed to the dominating protein ?-lactoglobulin. At pH 9, Young's modulus and stress at break are not affected when the concentration of ?-Lg, WPI, or S varies. At pH 7 and 8, Young's modulus and stress at break increase when the concentration of ?-Lg and WPI increases, and they decrease when the concentration of S increases. Strain at break increases when pH increases from 7 to 9, a more pronounced effect being observed for the WPI films. Water vapor permeability (WVP) decreases and increases for pH 7 and 9, respectively, as the concentration of ?-Lg and WPI increases. This contrast in behavior at different pH values is probably due to a structural difference that occurs above pH 8. Moisture content and WVP increase when S increases. Here a clear distinction can be observed between the two film materials: the ?-Lg films show higher values for both moisture content and WVP measurements.
|
|
| 3. |
- Ingemansson, T., et al.
(författare)
-
Multivariate evaluation of lipid hydrolysis and oxidation data from light and dark muscle of frozen stored rainbow trout (Oncorhynchus mykiss)
- 1995
-
Ingår i: Journal of Agricultural and Food Chemistry. - 0021-8561 .- 1520-5118. ; 43:8, s. 2046-2052
-
Tidskriftsartikel (refereegranskat)abstract
- Lipid hydrolysis and oxidation were evaluated by multivariate statistical methods in farmed rainbow trout (Oncorhynchus mykiss). The trout were acclimatized at 5 or 12°C and then frozen as fillets and stored at -15°C for up to 34 weeks. Results from analyses of lipid hydrolysis and lipid oxidation during frozen storage of light and dark muscle revealed that the major cause of lipid deterioration is hydrolysis. Hydrolysis resulted in an increase in free fatty acids by between 1 and 10%, particularly in the nutritionally important polyunsaturated n-3 fatty acids, 20:5 and 22:6. The phosphatidylcholine content of the muscle decreased by 25-50% during frozen storage. Phosphatidylethanolamine was stable in dark muscle but decreased in light muscle. By multivariate statistical evaluation it was possible to group the samples according to storage time or acclimatization temperature. A lower water temperature (5°C) resulted in reduced lipid stability during frozen storage. © 1995 American Chemical Society.
|
|
| 4. |
|
|
| 5. |
- Nilsson, Ulla, et al.
(författare)
-
Long-Term Studies of Fungicide Concentrations in Greenhouses. 2. Fungicide Concentrations in Air and on Leaves after Different Exposure Times and under Different Climate Conditions
- 1996
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 44:9, s. 2878-2884
-
Tidskriftsartikel (refereegranskat)abstract
- The decline of the two fungicides vinclozolin (formulation Ronilan FL) and triadimefon (formulation Bayleton Special) was studied in greenhouses. The decline of vinclozolin was also studied in climate chambers. In greenhouse experiments the fungicides were applied with either a low-volume sprayer or a high-volume sprayer, while in the climate chamber experiments the fungicide was applied with a pipet. Concentrations on leaves 1 day after spraying in the greenhouses with Ronilan FL were 0.87, μg of vinclozolin/cm2 and after spraying with Bayleton Special close to the detection limit (0.002 μg of triadimefon/cm2). Concentrations were higher on floors than on leaves. Air concentrations were higher immediately after low-volume spraying than after high-volume spraying but decreased rapidly. Air concentrations of vinclozolin during the first harvest, the third day after application, were below the detection limit (0.4 μg/m3). Climate chamber experiments showed no significant differences in residue decline rate between different climate conditions, with temperatures in the range of 18-26 °C and a vapor pressure deficit between 0.26 and 0.79 kPa.
|
|
| 6. |
- Nilsson, Ulla, et al.
(författare)
-
Long-Term Studies of Fungicide Concentrations in Greenhouses. 3. Exposure Risks after Spraying in Greenhouses.
- 1996
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 44:9, s. 2885-2888
-
Tidskriftsartikel (refereegranskat)abstract
- The study presented concerns the dermal exposure risks during harvest work in greenhouses after fungicide application. The contamination of the fungicide vinclozolin on clothes, overalls and gloves, worn during harvest after application was investigated. The fungicide was extracted from the cloth with 1-chlorobutane and finally determined with HPLC. The average amount of fungicide found on the clothes, the potential exposure, was 25 mg after 8 h of work in the greenhouse. It was estimated that most of the fungicide amount was found on gloves. Assuming a maximum uptake of vinclozolin (on bare skin) of 10%, the value of the dermal exposure was estimated to be 2.5 mg/day. In the absence of threshold values for dermal, exposure a comparison was made with recommended values for acceptable daily intake of foodstuffs. This comparison reveals that the assumed dermal exposure is higher than the value set by the U.S. Environmental Protection Agency but lower than the value given by the World Health Organization. Thus, the use of protective garments during harvesting, especially on the hands, is recommended.
|
|
| 7. |
- Papantoni, Margareta, et al.
(författare)
-
Long-Term Studies of Fungicide Concentrations in Greenhouses. 1. Technique for Determining Surficial Foliar Residues of Fungicides with Vinclozolin and Triadimefon as Model Compounds.
- 1995
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 43:1, s. 157-164
-
Tidskriftsartikel (refereegranskat)abstract
- A new analysis procedure for fungicides has been developed gearing toward estimation of worker exposure in greenhouses. The procedure includes sampling on leaves, glass, and polymers using vinclozolin and triadimefon as model substances and starts with solvation of the fungicides with ethanol from the surface. It proceeds by collection of the solution on disks of cloth, disk extraction with excess of ethanol, evaporation of the solution to dryness, and addition of 1-chlorobutane and ends finally with HPLC determination. Validations of the evaporation step, the desorption of analyte from the disks, and the whole procedure were performed separately. The whole procedure gave recoveries of vinclozolin and triadimefon on leaves of 74% (RSD 4.2%) and 79% (RSD 5.0%), respectively, and on hard surfaces around 90% (RSD ca. 6 %) for both substances. The losses in the evaporation and in the desorption step were small, the major losses occurring when the fungicide was collected from the surface. Also, some degradation products of vinclozolin and triadimefon, i.e., 3,5-dichloroaniline, triadimenol, and p-chlorophenol, were briefly studied.
|
|
| 8. |
- Persson, Hans, et al.
(författare)
-
Binding of Cu2+, Zn2+, and Cd2+ to Inositol Tri-, Tetra-, Penta-, and Hexaphosphates
- 1998
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 46:8, s. 3194-3200
-
Tidskriftsartikel (refereegranskat)abstract
- myo-Inositol hexaphosphate, the salt of myo-inositol hexaphosphoric acid (IP6), is a common constituent of many plant foods, such as cereals and legumes. IP6 interacts with mineral elements, influencing their bioavailability. Processed foods contain a mixture of different inositol phosphates, i.e., IP6 and its degradation products with five or less phosphate groups (IP5-IP1). The interaction of the lower inositol phosphates with mineral elements is not well-known. In this study, the interaction between metal ions (Cu2+, Zn2+, and Cd2+) and isolated fractions of inositol phosphates with 6, 5, 4 and 3 phosphate groups (IP6-IP3) was investigated by using a potentiometric technique. The study was performed at pH 3-7, which is the pH range in the upper part of the duodenum, where mineral absorption takes place. The inositol phosphate fractions studied had a pronounced binding capacity between pH 5 and 7. Thus, mineral complex formation with lower inositol phosphates is likely to occur in the duodenum, which would be important from a nutritional point of view. The mineral binding capacity as calculated per phosphate group was similar for IP6, IP5, IP4, and IP3, but the binding strength was lower for the lower inositol phosphates (IP4 and IP3). At increasing pH, within the range (pH 3-7), the metal complex formation generally began in the order copper, zinc, cadmium for all inositol phosphates indicating the same order of binding strength, i.e., Cu > Zn > Cd. For IP6 the difference was small between Cu and Zn.
|
|
| 9. |
- Pihlsgård, Per, et al.
(författare)
-
Chemical and sensory properties of liquid beet sugar
- 1999
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 47:10, s. 4346-4352
-
Tidskriftsartikel (refereegranskat)abstract
- Sensory analysis and headspace gas chromatography-flame ionization detection (GC-FID) analysis of liquid sugars (sucrose) designated for food- industrial use were performed in order to elucidate which compounds are responsible for perceived off-odors and off-flavors in liquid sugar. The liquid sugar samples investigated had various kinds of off-odors and off- flavors that might influence the quality of any food product in which they might be used, such as a jam or a soft drink. The sensory scores for the different attributes and the levels of different volatile compounds as measured by GC were analyzed for correlation using partial least-squares (PLS) analysis. A link between sensory analysis and GC analysis was thereby established, and compounds critical for the odor and flavor were identified using MS (mass spectrometry). Approximately 10 compounds were found to be correlated with the defined sensory attributes. Among these compounds associated with the sensory attributes were dimethyl disulfide, 2,6- dimethylpyrazine, 4-methoxyphenol, and 2,5-dimethylfuran.
|
|
| 10. |
- Skoglund, E., et al.
(författare)
-
Analysis of Inositol Mono- and Diphosphate Isomers Using High-Performance Ion Chromatography and Pulsed Amperometric Detection
- 1997
-
Ingår i: Journal of Agricultural and Food Chemistry. - 0021-8561 .- 1520-5118. ; 45:12, s. 4668-4673
-
Tidskriftsartikel (refereegranskat)abstract
- A rapid and sensitive high-performance ion chromatography method for separation and quantitative determination of inositol mono- and diphosphate (IP 1-IP 2) isomers using pulsed amperometric detection is described. The method involves extraction of samples with HCl, separation of inositol phosphates from the crude extract by anion-exchange chromatography, NaAc gradient elution in an NaOH environment to perform isomer separation on a high-performance anion-exchange column, and detection with pulsed amperometric detector. The applicability and sensitivity of the method is illustrated by measurement of the content of IP 1 and IP 2 in foods, human ileal contents, and enzymatic hydrolysis products of phytate (inositol hexaphosphate). The major IP 1 and IP 2 isomers formed during phytate hydrolysis with wheat phytase were shown to be Ins(2)P, DL-Ins(1)P, and DL-Ins(1,2)P 2 and with Aspergillus niger phytase, Ins(2)P and DL-Ins(1,2)P 2.
|
|
