A VIDEO-BASED METHOD FOR DETERMINATION OF AVERAGE STRESS-STRAIN RELATIONS IN UNIAXIAL COMPRESSION OF SELECTED FOODS

A video-based method was applied to evaluate average stress-strain relationships during uniaxial compression experiments of selected food materials. The determination of apparent Poisson ratios of Gouda cheese resulted in numbers close to the theoretical value for incompressible materials of 0.5. In case of such foodstuffs, mathematically corrected compressional stress based on the consideration of constant specimen volume showed almost similar results to stress values estimated on the basis of the true cross-sectional area measured from lateral extension. For compressible materials such as apples or bread, which show a certain reduction of volume under stress or strain, the apparent Poisson ratios were strain-dependent. Average stress values calculated from compressional force and actual specimen diameter were found to be different from either engineering stress and corrected stress.     

DIRECT SAPONIFICATION: A SIMPLE AND RAPID METHOD FOR DETERMINATION OF TOTAL CHOLESTEROL AND FATTY ACID COMPOSITION OF AQUATIC FOODS

Total cholesterol in aquatic foods was determined by direct saponification coupled with gas chromatography without derivatization. The direct saponification was compared with an AOAC extraction procedure and a culture tube extraction technique, both using chloroform:methanol (1:2, v/v) for extraction. Gas chromatography, high-performance-liquid-chromatography with UV detection of conjugated enone of cholesterol at 240 nm, and spectrophotometric o-phthalaldehyde method at 550 nm were compared to determine their effectiveness in cholesterol measurement. Direct saponification generally gave higher contents of cholesterol than the AOAC and culture tube extraction procedures, while quantification by the GC procedure appears to be the simplest method without sacrificing accuracy. Average percentage recoveries of cholesterol estimated with direct saponification-GC analysis in spiked fat-free catfish matrix and spiked fresh catfish muscle were 101.8 ± 9.6% and 101.7 ± 1.9%, respectively. The method may also be adaptable to food ingredients other than sterols such as the determination of fatty acid composition as demonstrated in this paper.     

FLAVOR SENSITIVITY OF SELECTED ANIMAL PROTEIN FOODS TO GAMMA RADIATION

Raw protein foods derived from 20 different species of animals of different biological classifications were irradiated with gamma irradiation over a range of doses. The intensity of irradiated flavor developed in each case was determined by an expert panel. Relative flavor sensitivities and threshold doses were estimated.     

QUANTITATIVE DETERMINATION OF FAT, PROTEIN AND CARBOHYDRATES OF SOY PRODUCTS WITH INFRARED ATTENUATED TOTAL REFLECTANCE

Attenuated total reflectance (ATR), offering a possible rapid method for quantitative measurements of major nutritional components in food materials (fat, protein, carbohydrate), was employed to evaluate the composition of a variety of soy products. Using a sample cell developed in this laboratory, different sample particle sizes and forces applied to a mounted sample were investigated to determine if variations of this type would improve the accuracy and precision of the quantitative ATR technique. Correlations of 0.96 for fat and 0.94 for protein were achieved between a chemical analysis and the infrared technique using a baseline absorbance (A') calculation and 120 mesh samples at 40 lb force. Errors assignable to various aspects of the ATR technique are discussed.     

超声提取-高效液相色谱法测定食品中碱性橙Ⅱ染料

建立超声提取-高效液相色谱法测定食品中碱性橙Ⅱ染料的方法.样品均质后,正已烷超声除去杂质,再用无水乙醇多次超声至无色,合并提取液浓缩离心,取上清液进行色谱分析.高效液相色谱仪采用C18柱,检测波长为449 nm.方法最低检出限为0.10mg/L,回收率超过98.5%,同一色谱条件下日落黄对碱性橙Ⅱ检出无影响.方法精密度分别为5.8%,6.2%及1.1%.     

INTERDEPENDENCY AND UNDERLYING DIMENSIONS OF SENSORY TEXTURAL CHARACTERISTICS OF SELECTED FOODS2

Sensory texture profile data for butters, cheeses, fish gels, frankfurters, peanut butters, raw potatoes, and baked sweet potatoes were subjected to principal component analysis to study the interdependence and the underlying dimensions of the sensory textural characteristics. The results indicated that the character notes used by the panel to describe the texture profile of each product were not entirely independent but formed a pattern of interdependency in the underlying dimensional structure. The texture profile could be described by about ½ the orthogonal factors (underlying dimensions) compared to the original character notes and still explain about 72% of the original variance. It is concluded that the texture profile analysis for each of the products in this study could be simplified by reducing the character notes being evaluated.     

ANTI-AMYLASE, ANTI-GLUCOSIDASE AND ANTI-ANGIOTENSIN I-CONVERTING ENZYME POTENTIAL OF SELECTED FOODS

α‐Amylase and α‐glucosidase have been targeted as potential avenues for modulation of postprandial hyperglycemia through mild inhibition of the enzymatic breakdown of complex carbohydrates to decrease meal‐derived glucose absorption. Water‐soluble extracts with optimized phenolic content of selected American and Asian foods were investigated for inhibitory activity against α‐amylase and α‐glucosidase, as well as angiotensin I‐converting enzyme (ACE), which has been linked to hyperglycemia‐associated hypertension. Porcine pancreatic α‐amylase (PPA) was allowed to react with each phenolic‐optimized food extract, and the derivatized enzyme–phytochemical mixtures obtained were characterized for residual amylase activity. The α‐glucosidase and ACE activities were determined in the presence of each phenolic‐optimized food extract. The amylase activity was inhibited more than the glucosidase activity in the presence of these phytochemical extracts, and more so by Asian foods than by American foods. The Asian spice ginger was found to possess strong ACE inhibitory activity in addition to significant anti‐amylase activity. The α‐amylase enzyme inhibition was positively associated with extract antioxidant activity and negatively with extract protein content. The significance of food‐grade, plant‐based amylase inhibitors for modulation of carbohydrate breakdown and control of glycemic index of foods in the context of preventing hyperglycemia and diabetes mellitus complications in the long term and ACE inhibitors for modulation of associated hypertension is hypothesized and discussed.     

INFLUENCE OF EXTRACTANT ON L-ASCORBIC ACID RECOVERY FROM SELECTED FOODS AND BEVERAGES

Recovery of L-ascorbic acid from selected vegetables, beverages and cereal was determined using up to 3 metaphosphoric acid-containing reagents, 3% trichloroacetic acid (TCA), and cold 0.05 Mperchloric acid (HCIO₄). Stability of ascorbic acid in these extractants was monitored over a 4 h holding period. All extractants yielded similar results for the beverages, however, TCA extracts of spinach and HCIO, extracts of tomatoes and cereal produced lower results than the other extractants. L-ascorbic acid content of green beans extracted with HClO₄, TCA, and 3% HPO₃, - 8% HOAC diffed from their initial values at 2, 4, and 4 h, respectively.     

DETERMINATION OF THE TOTAL LIPID CONTENT OF PORK RETAIL CUTS AT TWO EXTERNAL FAT TRIM LEVELS

Currently, retailers are required to conduct semi-annual or annual analyses of their labeled products under the USDA's Nutritional Labeling Verification procedures. The following study analyzed pork retail cuts that were trimmed to 0.0 cm or 0.64 cm external fat remaining. Lipid content was analyzed to determine the cuts that met "lean" (<10% total fat) and "extra-lean" (<5% total fat) specifications. The tenderloin, inside ham steak, and inside ham roast trimmed to 0.0 cm external fat remaining met the requirements for "extra-lean" labeling. The loin chop, loin roast, tip steak and tip roast trimmed to 0.0 cm external fat remaining, and the inside ham steak and inside ham roast trimmed to 0.64 cm external fat remaining, met the specifications for "lean" labeling.     

DETERMINATION OF TOTAL BROMINE AND OF BROMATE IN BARLEY AND MALT

Published methods for determining total bromine were found to be unsatisfactory or to require modification. Bromate may be determined directly on an aqueous extract of barley using an iodometric amplification reaction. Total bromine may be determined by the same reaction after ashing the sample in an oxygen combustion flask and oxidizing the bromide formed with hypochlorite to bromate.