Kinetics of Browning of Sultana Grapes

Heat inactivation of polyphenoloxidase (PPO) in sultana grapes between 83° and 98°C followed zero order kinetics with an activation energy of 13.7–16.7 kcal/mol. A high correlation (r = 0.973) was found between the residual PPO activity and darkness of the raisins (Hun-terlab L value) after drying at 50°C. Reaction rate for enzymatic browning increased with higher water activities while non-enzymatic browning showed the typical bell-shaped curve with a maximum around 0.8. Light-colored raisins were obtained without the use of SO₂ by pretreating the grapes with a 2 min dip in 93°C water that inactivated PPO and improved mass transfer through the skin. This latter effect was compared to that of other treatments such as ethyl oleate and caustic soda by drying studies and scanning electron microscopy.     

Changes in the Starch Fraction During Extrusion-cooking of Corn

Whole ground corn was extruded at 23.7, 18.5, 15.4,13.9 and 7.6% moisture contents (EMC). Decreasing EMC resulted in increases in water solubility index (WSI), enzyme susceptibility (ES), degree of gelatinization and blue values, while water absorption index and water insoluble carbohydrates decreased. ES and WSI of several blends prepared by combining raw (R), gelatinized (G), and dextrinized (D) corn were compared to those of extruded products. Corn extrudates had properties similar to blends containing G and D corn only. The relative proportion of D corn increased from about 10 to 60%, as EMC decreased. “Dextrinization” appears to become the predominant mechanism of starch degradation during low-moisture, high-shear extrusion. Viscoamylographs, scanning electron and light photomicrographs support these findings.     

RECONDITIONING OF POULTRY CHILLER OVERFLOW BY ULTRAFILTRATION

Poultry carcasses are chilled in water to lower the temperature rapidly. Water quality in the chiller is maintained by overflow and freshwater makeup. This in‐plant study evaluated reconditioning of chiller overflow by ultrafiltration for reuse in place of freshwater makeup. Trials with hollow fiber and spiral polymeric membrane modules were conducted to verify microbial rejection and to obtain flux characteristics. Microbial challenge trials conducted by using chiller overflow with artificially enhanced microbial levels reduced microbial counts by more than 5.4 log cycles. The rejection of chemical oxygen demand was over 73% and the reduction in turbidity was over 99.2%. These results verified that ultrafiltration produces water acceptable for reuse in the chiller to partially replace freshwater makeup. Concentration scans, pressure scans, velocity scans and time scans produced satisfactory permeate fluxes. Membranes cleaned easily after the trials. A 380‐L/min (100‐gal/min) spiral ultrafiltration system was designed assuming a 34‐L/m²h (20 gfd) average permeate flux based on flux characteristics observed during the trials. Economic assessment of the system operation indicated a 2.4‐year simple payback with possibilities for further improvement.     

DEVELOPMENT AND EVALUATION OF AN EXTRUSION-TEXTURIZED PEANUT PROTEIN

A commercial defatted peanut flour was analyzed for texturization properties in a Wenger X-25 extruder. Extrusion of the flour with addition of sodium stearoyl-2-lactylate resulted in a steady state operation and uniform texturized products. Functional properties of the extrudates such as water retention, hardness, and product integrity upon retorting: were similar to those of textured soy protein. Organoleptic properties of prepared patties (30:70 hydrated textured protein to meat ratio) were not different from the all-meat control for the analyzed sample; cooking losses and shrinkage were lower. Flavor was the most limiting factor for higher levels of incorporation and acceptance. A scanning electron microscopy study showed correlation between microstructure and the properties of the extrudates.     

A Physicochemical Model for Extrusion of Corn Starch

Corn starch extruded at 32.9, 29.2, 24.5, 22.5, 15.9 and 14.2% moisture was analyzed for expansion ratio, enzyme susceptibility, water solubility index, water absorption index, degree of gelatinization, paste viscosity and heat of gelatinization. A model system based on the combination of raw, gelatinized and dextrinized starch was used to represent the physicochemical properties of the extrudates. Reducing extrusion moisture content resulted in a progressive change from gelatinized-like to dextrinized-like properties. Maximum gelatinization was observed at about 28-29% moisture. Below 20% moisture, dextrinization becomes predominant during high- shear cooking-extrusion. Scanning electron micrographs also validate the assumptions of the model.     

QUATERNARY LIQUID EQULIBRIUM : WATER—PHOSPHORIC ACID—1— PENTANONE AT 25° C.

Liquid-liquid equilibrium, solubility and tie-line data, for the quaternary system Water-Phosphoric Acid-l-Pentanol-3-Pentanone, were obtained at 25°C and atmospheric pressure, using an analytical method. 1-Pentanol appears to be more effective than 3-Pentanone as extractant solvent of phosphoric acid. Advantages are not observed with the use of mixed solvents in the purification of wet process phosphoric acid by means of solvent extraction.     

A MIXED INTEGER LINEAR PROGRAMMING-BASED TECHNIQUE FOR THE ESTIMATION OF MULTIPLE GROSS ERRORS IN PROCESS MEASUREMENTS

This paper presents a new strategy for detecting, identifying, and estimating gross errors (measurement biases and leaks) in linear steady state processes. The MILP-based gross error detection and identification model is constructed aiming at identifying the minimum number of gross errors and their sizes. One significant advantage of the method is that the detection, identification, and estimation of gross errors can be performed simultaneously without using any test statistics.     

Rheological, Thermal and Microstructural Properties of Whey Protein-Cassava Starch Gels

Mixed gels of cassava starch (CS) and a whey protein isolate (WPI), obtained by heating solutions of 10% total solids, pH 5.75 to 85°C, were characterized as a function of the starch fraction, θ_s, by axial compression, small-amplitude oscillatory rheometry, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Gelation did not occur for θ_s > 0.7. In the range 0<θ_s < 0.4 mixed gels showed higher mechanical (E, elastic modulus) and rheological (G′, storage modulus) properties than pure gels, with maximum values for θ_s= 0.2–0.3. Viscoelastic measurements as a function of time showed that gels containing higher levels of WPI developed a larger G. Blends of both biopolymers showed independent thermal transitions in DSC measurements, related to gelatinization and denaturation. Microstructure of a mixed gel formed at θ_s= 0.2 showed a continuous matrix formed by strands of WPI particle aggregates and an independent CS phase.     

Properties of Mixed and Filled-type Dairy Gels

Skim milk powder (SMP), a whey protein concentrate (WPC) and fat globules with modified membranes were used for the fabrication of mixed and filled dairy gels. Firmness and syneresis of pure gels varied broadly with pH and total solids (TS). Mixing SMP and WPC at 10% TS showed synergistic effects on gel firmness, particularly for 50:50 blends, and addition of fat provided further reinforcement. Syneresis of gels and their appearance changed from high and clear to low and turbid, respectively, as the WPC content was increased. Microstructural studies revealed the porous structure of the parent gels, compatability between both protein sources and between fat globules and the protein matrix.     

LIQUID-LIQUID EQUILIBRIA FOR THE SYSTEM WATER-PHOSPHORIC ACTD-1-PENTANOL-3-PEHTAHONE AT 25°C IN THE PRESENCE OF SODIUM CHLORIDE.

A quantitative study of the effect of sodium chloride has been made on the quaternary liquid-liquid equilibria Water-Phosphoric Acid-i-Pentanol-3-Pentanone at 25°c and atmospheric pressure. Mutual solubility and tie-line data are obtained at saturation of sodium chloride in both conjugated phases. The addition of sodium chloride increases the distribution coefficient of phosphoric acid and the selectivity of extractant solvents for i-Pentanol and mixtures of 1-Pentanol and 3-Pentanone, whereas it has no significant influence when the extractant solvent is 3-Pentanone.