Cotyledon Structure of Resting Peanut (Arachis Hypogaea L. cv. Florunner) Seed Before and After Hydraulic Pressing

The cotyledon structure of resting peanut (Arachis hypogaea L. cv. Florunner) seed before and after hydraulic pressing was investigated with light and scanning electron microscopy. Observations were made of the appearance of cell walls and the major subcellular components: spherosomes (oil reserve bodies), aleurone grains and starch grains. Major findings include previously unreported cell wall damage and surface fissures that may be important to processors who express the oil from peanuts.     

Polyphenol Oxidase System in Red Delicious Apples

The polyphenol oxidase system (E.C. 1.14.18.1) in‘Red Delicious’apples (Malus domestica) was investigated. Polyacrylamide gel electrophoresis (PAGE) revealed two active isoenzymes as detected with pyrocatechol substrate. The crude enzyme extract (acetone powder) was found to have one optimum pH of 6.2 and one optimum temperature for the browning reaction of 30°C with the experimental conditions described. The Michaelis constant (Km) as an average of the two active enzyme forms was 2.2 × 10^?lM pyrocatechol and the average maximum velocity (Vmax) was 4.8 × 10^?l AA390 per minute.     

Establishing Thermal Processes for Products with Straight-Line Heating Curves from Data Taken at Other Retort and Initial Temperatures

Heat penetration data were obtained at high and low retort temperatures (RTs) and at high and low product initial temperatures in two can sizes for food products displaying straight-line heating curves in an agitating retort. The extrapolation of data to other RTs was found to be a safe practice for products heating with conduction or significant induced convection. Extrapolating to lower RTs for intermediate viscosity products slightly underpredicted required processing times. The effect of initial temperature was consistent with that found in a previous study for broken-heating products in a still retort, in that heat penetration tests conducted at different initial temperatures can have a significant influence on process establishment, depending on the product.     

Physicochemical Properties of Ovalbumin and Lysozyme Treated with Oleic Acid

Results from polyacrylamide gel electrophoresis confirmed that proteins were more negatively charged in the presence of oleic acid. The electrophoretic mobility of unmodified and modified lysozyme was of opposite but similar magnitude. Critical micelle concentration (50.0 μ M) of oleic acid suggested that association between the fatty acid and proteins was mostly hydrophobic. Muramidase activity of modified lysozyme and difference spectra of modified ovalbumin suggested that oleic acid was partially or totally surrounding the proteins. Improved freeze-thaw characteristics of treated egg white were attributed to greater negative charge and instability of proteins produced by oleic acid.     

Calpain-calpastatin and toughness in M. longissimus from electrically stimulated lamb and beef carcasses

Shear strength, pH, temperature, μ-calpain, m-calpain and calpastatin levels were measured over a two-week post-slaughter period in Longissimus lumborum et thoracis (LD) from six lamb and six beef carcasses. All carcasses were subjected to high voltage electrical stimulation. The toughness of the beef LD determined by a MIRINZ tenderometer at 24 h post-slaughter showed a strong correlation (r=0.91) with pH of the LD at 3 h. Beef LD toughness at 14 days was correlated (r=0.84) with initial m-calpain levels. In both lamb and beef, LD toughness at 4 and 14 days respectively was also correlated with initial levels of calpastatin (r=0.85, 0.83, respectively). The strong correlation between calpastatin and the rate of tenderisation indicates that the calpain system is closely linked to the proteolytic breakdown of myofibrillar proteins. There is also evidence of an interaction between pH and μ-calpain activity. The μ-calpain, m-calpain, calpastatin, pH and temperature kinetic changes which occurred during the post-mortem ageing of beef and lamb LD were applied to a computer program which predicted rate of meat tenderisation by calculating in situ calpain activity. The closeness of fit between the predicted rate of meat tenderisation and the observed tenderness values of beef and lamb LD indicates that the post-mortem activity of μ-calpain is the major determinant of variations in tenderness. However, application of the meat tenderisation predictive program to LD from individual animals revealed that the program was not sufficiently robust for this use.     

KINETIC ANALYLSIS OF THE FORMATION OF NITROSYLMYOGLOBIN

The formation of nitric oxide myoglobin (nitrosylmyoglobin) was followed in buffered solutions in which the concentrations of ascorbate, nitrite, chloride, myoglobin and hydrogen ion were varied systematically to determine their effect on the rate constants. The rate of formation of nitrosylmyoglobin was zero order with respect to the pigment. The orders for the other reactants were determined by plotting the zero order rate constants as functions of varying orders of each reagent to determine which order gave a linear plot. The results were used to develop a mechanism and a mathematical expression for the reaction. Two reaction sequences involving different nitrosating species were involved; 1, direct action of nitrous acid and 2, the formation of nitrosyl chloride. Both species then nitrosated ascorbate and ascorbic acid, by different mechanisms. The nitric oxide for nitrosylmyoglobin formation came from the nitrosated ascorbate.     

Carrot Dehydration—Optimization Process Studies on the Explosion-Puffing Process

A carrot dehydration process that includes the unique continuous explosion-puffing system (CEPS) is described. A drying study included moisture distribution throughout a two-stage pilot scale dryer as well as bed temperature during first stage drying. Shrinkage losses of carrots by two dehydration methods were investigated, and volume differences were obtained. Measurements of dried carrot properties such as bulk density, color, nonenzymatic browning, rehydration, and disintegration were used to determine optimum operating pressure, temperature, and feed moisture for CEPS. Response surfaces developed from these properties were used simultaneously to establish a constrained optimum.     

Oxidation of cholesterol in heated tallow

Preliminary thin layer and gas chromatography data indicate that tallow cholesterol is oxidised when tallow is exposed to high temperatures (180°C) for an extended period. This may be of some significance to human health since some of these oxidation products may be angiotoxic and/or carcinogenic and tallow is used as a deep-fat frying medium in some fast-food restaurants.     

Some changes in the constituents upon heating a model meat flavour system

Percentage changes in the amino acid content upon heating with different components in a synthetic model meat flavour mixture were followed during different stages in development of the system. Heating of ten different amino acids with a simple sugar mixture (glucose, ribose and xylose) resulted in losses of approximately 95, 58, 38 and 37% of the cysteine, methionine, leucine and isoleucine, respectively, whereas the other amino acids decreased by 19–31%, but the ammonia (NH₃) content by only 5%. On heating gelatin with the simple sugar mixture, tyrosine and phenylalanine losses amounted to about 58 and 40%, respectively, while the other amino acids declined by 27–37% and the NH₃ content by some 12%. Heating of the composite model system (gelatin, added amino acids and simple sugars) resulted in losses of about 94, 60 and 55% of the cysteine, methionine and histidine, respectively, while the other amino acids decreased by 20–35% and the NH₃ content by 15%. The possible role of some of the amino acids in the development of the synthetic meat flavour system is discussed in view of these findings.     

MULTI-RESIDUE DETERMINATION AND CONFIRMATION OF TEN HETEROCYCLIC AMINES IN COOKED MEATS

Heterocyclic aromatic amines (HAAs) have been identified in various cooked meat products. HAAs are formed from pyrolysis of proteins and amino acids and are of interest because many of these primary arylamines are mutagens and rodent carcinogens. We developed a screening method for ten HAAs using liquid-liquid extraction, reverse-phase HPLC separation, and tandem electrochemical (ECD) and fluorescence (FLU) detectors. This detection system exhibited greater sensitivity (50-100 fold) for HAAs than the HPLC-UV methods. HPLC-FLU has detection limits of 100 pg to 1 ng for six HAAs, and HPLC-ECD detection limits of four HAAs were 250 pg to 1 ng. We also developed a confirmatory procedure for ten HAAs using HPLC coupled to positive ion APCI-MS. This technique has subnanogram detection limits. These methods were used to quantify HAAs in meat products at levels formed by typical Western cooking methods.