A soybean oil, a hydrogenated vegetable frying shortening and an animal‐vegetable shortening were heated at 190 C for 8 hours each day for 4 days with and without the frying of potatoes. Samples were taken periodically and analyzed for various changes normally used to measure frying oil deterioration. The changes in the dielectric constant were determined with a patented instrument called the Food Oil Sensor. This instrument is standardized with 3. sample of the fresh oil, and it then measures the change in the electric capacitance of the heated oil samples. The dielectric constant of all three shortenings increased linearly with heating time. The greatest change occurred in the soybean oil sample and the smallest change in the hydrogenated vegetable shortening. For each shortening the increase was somewhat greater during frying than during heating without frying. Statistically significant correlations were obtained between instrument readings and increase in the total polar materials, the color, the peroxide values, the diene content, and the free fatty acids and the decrease in the iodine values.

A comparison is made between a spectrophotometric method and a high-pressure liquid chromatography (LC) method for tryptophan content of a variety of foods. The spectrophotometric method has an RSD of 2.53%. The LC method has an RSD of 2.03% with a recovery of 95.5 ± 2.4% for spiked samples. The mean tryptophan content of 18 samples by the spectrophotometric method was 0.38%, and that by the LC method was 0.35%.Among the major challenges facing the food chemist today is the need for more accurate and cost-effective methods for nutrient analysis. Spectrophotometry and/or high-pressure liquid chromatography (LC) when coupled with appropriate sample preparation and workup procedures meet these criteria.One of the nutritionally essential amino acids, tryptophan, has been analyzed by a variety of methods in the past. These methods have been reviewed by Friedman and Finley (1971). One of these methods, studied thoroughly by Spies (1967), which utilizes Pronase hydrolysis, derivatization with p-(dimethylamino)benzaldehyde, and spectrophotometric measurement appears to be well suited for food products. Tryptophan has also been measured by LC in biological samples by a variety of methods. These include separation on copolymer packings (Lefebvre et al.,

2)where ( A~~~) s D S = X is the area at finite detergent concentration; (Az@)sDs=o is the area at 0 detergent concentration.From Table 111, Fs decreases as SDS increases to 0.5 and then levels off for cut 1. Moreover, the arithmetic products of Fs and total nitrogen (Le., total nitrogen resolubilized) in cut 1 are 11.8, 9.6, 6.4, and 11.7 mg, respectively at 0, 0.2, 0.5, and 1% SDS. Therefore, SDS increases extractability and initial solubility, but decreases resolubility for cut 1 (see Fs, Table 111). Cuts 2 and 3 are completely soluble at all detergent concentrations within experimental error. The solubility results for all cuts agree with qualitative visual observations. CONCLUSIONSThe nitrogenous constituents of freeze-dried Coastal Bermuda grass can be classified as insoluble (RI), extractable-insoluble (RII), extractable-temporarily soluble (SDS extractable cut l), extractable-soluble (cut 1 at 0% SDS, cut 2, and cut 3). These classifications serve as a functional method of determining the end use of forage protein for maximum utilization as food or feedstuff. Cut 1 soluble (NT = 11%); and possibly cuts 2 and 3 (NT 18%) might be made suitable for human use. Cut 1, SDS extractable (NT = 28% at 1% SDS), cut 2 and 3, and possibly RII (NT N 5% at 1% SDS) might serve as a protein source for monogastric animals and RI and RII (NT N 40% at 1% SDS) for ruminants.The degradation or precipitation of cut 1 could be minimized by separating it, before the chloroplastic proteins are solubilized and with the utmost rapidity, from cuts 2 and 3. Here, cut 1 was separated from cuts 2 and 3 in less than 4 h from the start of the extraction. Since NT, percent CP, molecular weight distribution parameters (Table 11), solubility parameters (Table 111), and the content of aromatics (Table 111) are independent of SDS concentration for cuts 2 and 3, a two-stage procedure apparently would be appropriate: stage 1, extract with buffers, antioxidant and mild conditions to separate RI and RII from cuts 1-3; stage 2, extract RI and RII with harsher conditions (e.g., detergent, pressure, heat, organic solvents, etc.) which would separate maximum chloroplastic protein.ACKNOWLEDGMENT sample extractions and analyses.

A high pressure liquid chromatographic (HFLC) method for determining 5 common carbohydrates in food products was evaluated. Reproducibility data were generated showing a relative standard deviation of 2.8%. Recovery studies on a variety of foods gave an average recovery of 98.8%. The HPLC data for 3 varieties of ready-to-eat cereals were compared with data from 4 independent laboratories using current AOAC chemical methods. The HPLC mean values differed from the chemical mean values by 3.2%.

A simple method employing simultaneous extraction and oxidation has been developed for the semiautomated determination of ascorbic and dehydroascorbic acids in food products. Recovery studies were conducted on ready-to-eat breakfast cereals and both fresh and canned fruits and vegetables, with average recoveries of 101, 100, and 102%, respectively. Reproducibility data were generated showing a relative standard deviation of 3.5%. The automated method was compared with the manual AOAC fluorometric method and with indophenol titration ; correlation coefficients were 0.9960 and 0.9926, respectively. The hydrolysis product of dehydroascorbic acid, 2,3-diketoguIonic acid, a reported interference in this method, was prepared and shown not to form an interfering fluorescent derivative.