Composition of Raw and Cooked Potato Peel and Flesh: Amino Acid Content

The nitrogen and total amino acid contents of Katahdin and Pontiac varieties of potatoes are reported for the peel and flesh, before and after cooking. With the exception of glutamic acid and 7-amino-butyric acid, all of the contents were higher in the peel. Losses of nitrogen and amino acids were minor in boiling whole potatoes but greater in oven baking in the peel or in boiling the peeled potato. Microwave cooking losses were less than in oven baking.     

Sweetness of α-, β-, and Equilibrium Lactose Relative to Sucrose

The sweetness of α-, β-, and equilibrium lactose, measured by a trained panel using paired comparison with standard reference solutions of sucrose of concentrations from 0.50–6.50%, ranged from 30–35% that of sucrose. The sweetness of β-lactose was 105–122% that of α-lactose. The predicted swweetness of lactose at mutarotation equilibrium, calculated from sweetness values for α- and β-lactose and from the relative amounts present as determined by polarimetry, i.e., 38%α and 62%β, did not differ significantly from the experimentally determined sweetness value, indicating an absence of synergism for sweetness in mixtures of α- and β-lactose. Isosweet sucrose concentrations for three different concentrations of β- and equilibrium lactose and two concentrations of α-lactose are reported.     

Forced Air Drying of Partially Freeze-Dried Compressed Carrot Bars

The quality of compressed carrot bars produced by combining freeze drying with air drying was investigated. Quality parameters measured were color, texture, rehydration ratio, carotene, ascorbic acid, alphatocopherol, and sensory acceptance. It was found that a high quality compressed carrot bar could be obtained by freeze drying to 20–40% moisture, equilibrating with microwave energy, compressing, then air drying at 60°C. The scanning electron microscope proved useful in delineating reasons for differences in texture and rehydration.     

Two Lipoxygenases from Germinated Barley-Heat and Kilning Stability

Using ammonium sulfate precipitation followed by hydrophobic and ion exchange chromatography, two lipoxygenase isoenzymes, LOX 1 and LOX 2, were 18.3- and 44.5-fold purified from germinated barley, with 18 and 24% recovery of activity respectively. LOX 1 and LOX 2 were characterized by isoelectric points 4.9 and 6.4, and molecular weights of 90 kd and 110 kd, respectively. Apparent Km values for linoleic acid were 0.06 mM for LOX 1 and 0.18 mM for LOX 2. LOX 1 converted linoleic acid to 9 and 13 hydroperoxides at about 4:1, whereas the 13 hydroperoxide was the major product formed by LOX 2 (ratio 3:7). For both isoforms, thermal inactivation data indicated first order kinetics with activation energies influenced by ionic strength and pH. Isoenzymes composition was analyzed for three kilning schemes: the 1:3 ratio between LOX 1 and LOX 2 observed in germinated barley increased during the course of kilning.     

Inhibition of Horse Bean and Germinated Barley Lipoxygenases by Some Phenolic Compounds

Phenolic compounds have been repeatedly implicated as potent antioxidants. Efficiency has been frequently estimated by radical scavenging activity and few reports have considered lipoxygenase (LOX) inhibition. Horse bean LOX was inhibited by a range of phenolic acids, gallates and flavonoids. All compounds tested were uncompetitive inhibitors with the exception of flavonol aglycons which were non competitive type. In each class of compounds, inhibition constants were strongly affected by structures. Inhibition patterns of (-)-epicatechin on germinated barley LOXs were detailed: (-)-epicatechin acted as an uncompetitive inhibitor while (-)-epicatechin reduced hydroperoxide formation by its radical scavenging activity and thus limited enzyme activation.     

A Sample Bias in the Evaluation of Smoked Frankfurters by the Triangle Test

SUMMARY— A taste panel was able to determine the difference between smoked and unsmoked frankfurters, at a statistically significant level, only when the smoked frankfurter was the "odd" sample; non-significant selections were made with the unsmoked frankfurter as the "odd" sample. Positional differences of the "odd" sample in tasting the three samples did not affect its selection. Determination of difference between two food products by the triangle taste panel test can be affected by the choice of sample for the "odd" sample.     

Loss of Amino Acids and Water Soluble Vitamins During Potato Processing

Processing potatoes to potato flakes almost totally eradicated ascorbic acid, but better than 50% of the original amount of riboflavin and niacin was retained. Thiamin content of potato flakes can vary from 0-65% of its amount in the raw potato depending on the amount of sulfite added during processing. If sulfite addition is controlled, a 100g portion of rehydrated potato flakes can supply about 1/6 of the Recommended Dietary Allowance of thiamin. Some losses of arginine, aspartic acid, glutamic acid, and gamma aminobutyric acid occurred during hot water blanching, and a significant loss of methionine occurred during drum drying. However, amino acids can be considered quite stable during potato flake production.