THE DETECTION OF SOYBEAN FLOUR IN COCOA POWDER

Protein analysis is evaluated for determining the presence and content of soybean flour which is used as an adulterant in cocoa powder. The coefficients of the determination were significantfor estimating the level of adulteration. A protein scale is developed for quantitative measurement of soybean flour in cocoa powder.     

INSTRUMENTAL DETERMINATION OF ELASTICITY OF MARSHMALLOW 1

Marshmallows of a national and supermarket brand were subjected to four successive compression-decompression cycles using a computer interfaced Universal testing machine and the total and recoverable work in each cycle determined. The two brands were significantly different. Differences were maintained irrespective of the deformation rate (10 and 20 mm.min^–1), the magnitude of imposed strain in the range of 15–40% and the time between the cycles (0, 30 and 60 s). It appears that the discriminatory power of the test decreases as the magnitude of the imposed strain increases.     

Alginate Texturization of Highly Acid Fruit Pulps and Juices

Apple pulp and reconstituted grapefruit juice were provided as texturized alginate gels at concentrations of 5–96%, after pH adjustment. The resulting products had appreciable mechanical integrity even at very high pulp or juice concentration. Their texture, judged by compressive strength, strain at failure, and deformability modulus was improved considerably by dipping in calcium lactate solution. The original pH of the fruit could be restored by a dip in a citric acid solution without adverse effects on texture.     

THERMAL CONDUCTIVITY MODELS FOR POROUS BAKED FOODS

Models for the thermal conductivity of porous food were developed by modifying the parallel model to include structural data such as pore diameter, pore wall thickness and shortest path ratio. The predictions from these models and 12 literature models were compared to values determined for 12 porous foods. The models from the literature considered the air volume fraction but no other structural information. The proposed parallel, Kopelman random (KR) and Kopelman fibrous parallel models gave predictions that were not significantly different from the experimental thermal conductivity. All acceptable models except the KR model are variations of the parallel model, indicating that heat flows in parallel through the air and solid portions of porous foods. Regression analysis determined that only the thermal conductivity of the solid and shortest path ratio significantly correlate to the final thermal conductivity, indicating that the configuration of the pores is important in porous foods.     

RECOVERABLE WORK VERSUS ASYMPTOTIC RELAXATION MODULUS IN AGAR,CARRAGEENAN AND GELLAN GELS1

Cylindrical specimens of agar, carrageenan and gellan gels (1&2%) were uniaxially compressed to various predetermined strain levels and then decompressed. In an independent set of tests, specimens of the same gels were compressed to the same strains and then allowed to relax. Both the percent recoverable work, calculated from the stress-strain relationships in the compression-decompression cycles and the magnitude of the asymptotic relaxation modulus, calculated from the normalized and linearized relaxation curves, decreased as the strain increased. In all three gels there was a linear correlation between the percent recoverable work and the magnitude of the asymptotic modulus at corresponding strains, a sign that both parameters are indicative of these gels’ degree of elasticity and the latter's strain dependency.     

"Degree of Elasticity" Determination in Solid Foods

Specimens of a variety of foods (banana, cheese, frankfurter, jelly candy, marshmallow, and potato) were subjected to four compression-decompression cycles at two prefailure deformation levels (12.5–15 and 20–25%). Total and percent recoverable work in each cycle were determined using a universal testing machine interfaced with a computer. The magnitude of recoverable work, its strain dependency and response to successive cycles were characteristic of each material. Percent recoverable work was unrelated, however, to strength (stress at failure), deformability, and stiffness. The general level of recoverable work was about 60–80% of total work in the materials commonly considered “elastic” and 20–50% in those known as “plastic.”