The Aging and Tempering of Iron-Nickel-Carbon Martensites

The aging and tempering of freshly quenched (M_s > RT) and virgin (M_s < RT) martensites with lath and plate morphologies in Fe-Ni-C alloys have been studied to obtain kinetic and structural information. At subambient temperatures, the first change is attributed to isothermal conversion of a small amount of retained austenite or to slight relaxations in the martensite, but this is not a significant part of the martensite aging process. Aging above ?40 °C to about 70 °C is accompanied by the diffusion-controlled clustering of carbon atoms, resulting in an increase in electrical resistivity proportional to the carbon content but independent of the martensitic morphology. This regime is followed above 100 °C by the precipitation of ε-carbide (i.e., the conventional first stage of tempering), which may emerge directly from the carbon-rich clusters. At still higher temperatures, cementite forms separately (i.e., the conventional third stage of tempering) in competition with the ε-carbide. These two precipitation processes overlap, and their kinetics appear to be controlled by iron-atom diffusion away from the growing carbide particles along dislocation paths. No evidence was found in this investigation for a regime reflecting carbon migration to dislocations or other defects, but this possibility is not ruled out by the experimental methods employed.     

TEXTURAL AND MICROSTRUCTURAL PROPERTIES OF RENNET-INDUCED MILK COAGULUM AS AFFECTED BY THE ADDITION OF SOY PROTEIN ISOLATE

The effect of the addition of soy protein on the textural properties and microstructure of reconstituted nonfat dry milk coagulum with time after rennet addition was studied using an Instron Universal testing machine with a newly developed test cell, and by scanning electron microscopy. Soy protein added to reconstituted nonfat dry milk at 5% of the total solids resulted in a reduction in firmness, a decrease in syneresis and a looser microstructure of the coagulum at any given time up to two hours after rennet addition as compared to the control without added soy protein. An increase in the level of soy protein to 10 and 20% of the total solids resulted in a further reduction in coagulum firmness and in syneresis. Syneresis was also followed during changes in coagulum firmness. Analysis of the textural as well as microstructural data suggests that changes in coagulum firmness and syneresis of rennet-induced milk coagulums (with or without added soy protein) with time after rennet addition were associated with the extent to which casein micelles coalesced during coagulum formation. The Instron test and the syneresis test developed in this study were simple and practical.     

Effect of Preprocessing Treatments on the Firmness and Quality Characteristics of Whole and Sliced Strawberries After Freezing and Thermal Processing

Procedures designed to improve fruit firmness of overripe strawberry fruit originally designated for the fresh market were investigated. The firmness of ‘Cardinal’ strawberries was increased by soaking or vacuum infiltrating in 1 or 2% Ca lactate solutions. Calcium lactate was more effective in firming sliced than whole fruit. Thermally processed fruit benefited more from calcium absorption than did the frozen, thawed fruit. Whole fruit firmness was increased by the vacuum infiltration of Ca lactate. There was little increase in firmness of the sliced fruit when the calcium was vacuum infiltrated as compared to a soak treatment with no vacuum. There were slight but significant differences among treatments on all quality attributes tested. However, these quality differences would have no commercial importance.     

Effect of Combining Mechanically Harvested Green and Ripe Puree and Sliced Fruit, Processing Methodology and Frozen Storage on Quality of Strawberries

Small green and ripe mechanically harvested strawberries were processed into puree and combined with 60 and 80% sliced ripe fruit to determine the effects of holding after harvest, percent green fruit in puree, processing procedure and storage on quality of frozen sliced strawberries. Green and ripe fruit puree added to the sliced strawberries resulted in higher viscosity and lower ascorbic acid, total anthocyanins and red color as compared to packs with 100% sliced ripe fruit. The mixtures of sliced ripe fruit and up to 40% puree were rated acceptable by a sensory panel. Heating the puree may be beneficial to color during long-term storage. Holding of fresh strawberries for 24 hr at 24°C after cleaning decreased the ascorbic acid, viscosity of syrup and color of the frozen pack. Storage of the frozen product decreased ascorbic acid and color.     

CONSUMER ACCEPTABILITY OF PROCESSED OSTRICH MEAT PRODUCTS

Two value-added ostrich meat product prototypes were prepared and evaluated by a consumer panel (n = 132) against similar products manufactured entirely from pork. Ostrich "ham" and a control pork ham product were prepared by a traditional ham cure, and Polish sausage products were formulated with either all-pork or a 67% ostrich/33 % pork blend and processed with a commercial spice blend. Ostrich "ham" tended to be rated lower (P = 0.0537) in salt intensity, but had higher flavor intensity ratings. Consumers gave pork ham more favorable ratings for overall acceptability (P< 0.01) and flavor acceptability (P< 0.05). For Polish sausage products, overall acceptability, flavor acceptability, flavor intensity, salt intensity, texture and tenderness were not different (P > 0.05) between all-pork and ostrich/pork varieties. Results indicate that value-added ostrich meat products were more acceptable when they were more finely ground, spiced, and combined with pork in a sausage product than when they were prepared as a "ham" product.     

Effects of fining agents on trans-resveratrol concentration in wine

Resveratrol has been identified as a wine component related to moderate wine consumption and a reduction in serum cholesterol levels. Processes such as wine fining that result in loss of resveratrol during winemaking are therefore of interest, and led to these present studies. A number of agents were compared and were found to lower resveratrol levels in all wines to some extent. Results from two studies (1996 and 1997) are reported. The standard addition method was used in combination with High Pressure Liquid Chromatography to calculate resveratrol levels. In Study 1 (1996), recommended maximum levels of all fining agents (Level 3), bentonite, egg white, gelatin + kieselsol and polyvinylpolypyrrolidone (PVPP), lowered resveratrol levels significantly compared to controls (Level 0). Nevertheless, addition of fining agents at Level 0 resulted in resveratrol levels that were significantly higher than those at Level 3, but resveratrol levels in wine from Level 0 were not significantly different from Level 1. In Study 2 (1997), carbon + egg white, and gelatin + kieselsol fining was studied, and their effects differed according to grape variety. Least removal of resveratrol by carbon fining occurred in wine from Cabernet Sauvignon (Vitis vinifera) whereas most removal occurred in wines from Cynthiana (Vitis aestivalis) and Noble (Vitis rotundifolia). Resveratrol levels of control wine were significantly higher than resveratrol levels of wine treated with recommended maximum addition of fining agent in all varieties. Taken overall, any addition of any fining agent lowered resveratrol levels in all wines to some extent, but complex interactions between fining agent and wine variety resulted in different regression trends. While recognising the constraints set by our particular data that could reflect unique circumstances, we are nevertheless able to infer from these trends that low levels of fining agents can be used without statistically significant loss of resveratrol.     

EVALUATION OF WINE GRAPES FOR SUITABILITY IN JUICE PRODUCTION1

Chemical and sensory analyses were designed to evaluate 14 traditional wine grapes grown in Arkansas as to their suitability for varietal grape juice. Six were classified as red or pink grapes: Chancellor, Cabernet Sauvignon, Villard noir, Gewurztraminer (pink when heated), Cynthiana, and Noble, and seven were white grapes: Aurore, Cayuga, Carlos, Chardonnay, Seyval, Vidal, Verdelet and White Riesling. Concord (red) and Niagara (white), traditional juice grapes, were also included in the study. All were processed by immediately pressing, heat processing at 60°C, heat processing at 80°C, and 24 h skin contact following pressing. Juices were evaluated 1 month after processing and again after 5 months storage at 37°C. The preferred treatments for white grape juices were the immediately pressing treatment of Niagara and Aurore and the 24-h skin contact treatment of Niagara, Verdelet and Vidal. Only the flavor of Verdelet and Aurore were ranked as high as the Niagara by a trained sensory panel. Generally, a nonheat treatment was ranked highest for flavor of the red juices, with the exception of Gewurztraminer, a pink juice when heated. Except for Villard noir, all of the red juices were ranked as good or better than Concord. White cultivars were closely ranked for color, with Vidal and Chardonnay being ranked lowest after storage. Heat treatments were generally ranked higher than nonheat treatments in color for the red and pink juices. Chemical analyses of the juices indicated that all cultivars were harvested within an acceptable pH range.