Sweetened Extruded Corn/Soy Product as Intermediate Moisture Food

An intermediate moisture food analog of sweetened condensed milk was developed based on soy protein, modified degermed corn, vegetable oil and sugar. Water solubility of corn was increased by extrusion-cooking followed by saccharification with glucoamylase in a 28% total solids (TS) soy protein-extruded corn suspension. Enzyme-modified corn/soy concentrates with 40–45% TS had a water solubility index (WSI) of 56–58% and a DE of 38–40. The final products had 73.5–78.4% TS, 71.5–72.7 WSI at pH 4.1–4.2, and a water activity of 0.82–0.83.     

Thiamin Stability in Simulated Intermediate Moisture Food

Four different intermediate moisture model systems (IMMS) were designed and prepared to simulate intermediate moisture foods. Stability of thiamin hydrochloride in IMMS as a function of temperature, oxygen, a_w, moisture content and composition of the model systems was studied. Analysis of kinetic data indicated that the rates of degradation of thiamin (1) can be represented by a first order model, (2) were not affected by oxygen concentration and presence of riboflavin and niacin, (3) obeyed an Arrhenius relationship for temperature dependence in the range 25-60°C, (4) increased as polarity of the reaction medium decreased, and (5) decreased as a_w increased from 0.65 to 0.85.     

Thermal Degradation Kinetics of Pyridoxine Hydrochloride in Dehydrated Model Food Systems

The thermal degradation kinetics of pyridoxine hydrochloride were examined using a dehydrated model food system designed to simulate a ready-to-eat breakfast cereal. This study was carried out to provide information useful in estimating the thermal losses of pyridoxine hydrochloride in the processing of breakfast cereals and other low moisture dehydrated food systems. Portions of the model system which were fortified with pyridoxine hydrochloride were toasted in a conduction oven at 155°, 170°, 185°, and 200°C for a minimum of six heating times at each temperature. Pyridoxine (PN) content was determined in the heat treated model systems by high performance liquid chromatography (HPLC). For each heat treatment, the loss of pyridoxine could be described by a first order kinetics model. The first order rate constants for 155°, 170°, 185°, and 200°C were 1.74 × 10^?2 min^?1, 5.22 × 10^?2 min^?1, 16.88 × 10^?2 min^?1, and 48.95 × 10^?2 min^?1, respectively. The calculated Arrhenius activation energy was 29.8 Kcal/mol. In comparing the HPLC method to the standard microbiological assay, the HPLC assay gave lower PN values for the toasted model system. To explain this discrepancy, HPLC fractions were collected and analyzed by the microbiological assay. No significant vitamin B₆ activity was found in any fraction other than that containing the PN peak. It is possible that the milder extraction procedure used in the HPLC assay is less capable of recovering forms of PN which may become bound during the toasting process. These potentially bound forms may or may not be biologically available.     

Accelerated Kinetic Study of Aspartame Degradation in the Neutral pH Range

The degradation of aspartame in solution as a function of temperature (70–100°C), buffer concentration (0.01–0.1M phosphate), and pH (6–7) was studied in order to estimate losses during thermal processing and storage of aseptic milk-based drinks. Prior data have been mostly on acid carbonated beverages. First order rate constants were obtained in all the conditions with activation energies in the range 14–20 kcal/ mole. An increase in both pH and buffer concentration caused an increase in rate of loss. These data were used to predict losses that would occur during pasteurization and sterilization conditions. Experiments at 4 and 30°C showed significant losses would occur during 4 and 30°C temperature storage and extrapolation from high temperatures predicted faster degradation rates than those found.     

A Method for the Determination of Diffusion Coefficients of Food Components in Low- and Intermediate Moisture Systems

A simple set-up to measure translational diffusion of components in low moisture systems is described. The tracer technique was tested on the diffusion of ¹⁴C-labeled tripalmitin and palmitic acid in a model system containing paraffin oil, microcrystalline cellulose and gum arabic. Different methods to evaluate the apparent diffusion coefficients from the experimental diffusion curve were compared. Good results were obtained using a curve-fitting procedure based on the sum of least squares. The technique appears to be suitable for measuring diffusion coefficients up to 10^?9 cm²/sec. The procedure offers the possibility to quantify the mobility of chemical components in dried foodstuffs in order to elucidate the mechanisms and kinetics of reactions occurring during storage.     

Heat-induced Egg White Gels as Affected by pH

The functional properties of heat-induced egg white gels were investigated at five pH values. Textural characteristics were determined using the Instron Universal Machine. Hardness, elasticity, cohesiveness, chewiness, and fracturability were maximum at pH 11. Hunter L values were maximum at pH 5 and 7. Microstructure studied with electron microscopy was distinctly different at the five pH values. Alkaline gels showed a fine ordered network that might have contributed to excellent textural characteristics. Water-holding capacity (WHC) was high at alkaline pH, but decreased with addition of 2-mercaptoethanol, suggesting that disulfide bonds were important in egg white gels. Sodium dodecyl sulfate (SDS) improved WHC at pH 7 and 9. No significant correlation was observed between textural profiles and WHC.     

Moisture Retention and Textural Properties of Ground Chicken Meat as Affected by Sodium Tripolyphosphate, Ionic Strength and pH

Batches of ground chicken meat were mixed with 10% solutions containing 0.0–5.0% sodium tripolyphosphate and sufficient NaCl to adjust the ionic strength (IS) of the solutions from <0.7 to 6.0 at pH 6.5 to 9.5 in a 6 × 4 × 7 factorial experimental design. Patties prepared from the mixtures were evaluated for pH, cooking loss, and objective texture characteristics. Most effects of STPP were attributable to the direct effect of STPP on IS. However the ability of the phosphate to alter textural properties was greater at a pH value near the pK_a of the phosphate.     

Surimi Gel Colors as Affected by Moisture Content and Physical Conditions

Colors (CIE L*, a*, and b*) of Alaska pollock (7′heragra chalcogramma) and Pacific whiting (Mecs productus) surimi gels were evaluated and related to compositional and physical conditions during preparation and measurements. Ten samples were used in each treatment. Water addition, sample size, species, cooking and test temperatures, and freeze/thaw affected lightness (L*) and yellowness (b*) values, while outside light conditions at measurement did not affect colors. Greenness (-a*) values were less affected by all conditions.     

Extrusion of Soybean and Wheat Flour as Affected by Moisture Content

The effect of moisture content (MC) on texture and properties of extrudates with varied ratios of soybean flour (SF) and wheat flour (WF) was studied. A single-screw extruder was used at screw speed 200 rpm. MCs of blends were 16, 17 or 18%, w.b. The properties of extrudates depended on flow rate of the material during extrusion. The flow rate revealed a nonlinear dependence on the blend composition and the MC at the same volume of filling of the screw feeding section. The expansion ratio of WF or SF extrudates increased with lowering of the MC. Unexpectedly, the expansion ratio decreased with lower MC for the composite extrudates. Optimal extrudate properties at 16% (w.b.) MC corresponded to 80, 90 or 100% (d.b.) WF and 20, 10% or no SF, respectively. At 17 and 18% MC, optimal properties were found for products containing 80 or 90% WF and 20 or 10% SF, respectively.     

Carrageenans in Beaker Sausage as Affected by pH and Sodium Tripolyphosphate

We investigated effects of meat pH or sodium tripolyphosphate (STPP) on performance of carageenans (kappa, iota or lambda) in low-fat beaker sausage model systems. Adding STPP or using high-pH meat affected performance of the meat batter in similar ways. High-pH meat batters or those containing STPP had lower force values when extruded, lower cooking losses, and were firmer when cooked. The addition of lambda-carrageenan produced the softest texture. Kappa- and iota-carrrageenan improved water retention of low-pH meat batters. After staining, light microscopy revealed different structural effects of the carrageenans.     

Pectic Substance Degradation and Texture of Carrots as Affected by Pressurization

Heated pectin was degraded by transelimination (β-elimination) above pH 5 and by hydrolysis below pH 2, but pressurized pectin did not degrade. Thus cooked carrots decreased in firmness, but pressurized carrots did not. Pressurizing above 200 MPa slightly increased rupture strain. Galacturonic acid levels decreased in carrots cooked for 30 min. Total pectin in pressurized carrots was the same as in cooked for 3 min. However, with increased pressure, the amount of high methoxyl pectin in carrots decreased while low methoxyl pectin increased. Thus, the effects of pressurization on pectin degradation (transelimination) and texture of carrots were different from those of heating.     

Triglyceride Distribution in a Low Moisture Food Model System

A coherent view on the distribution of triglycerides in a multicomponent multiphase food model system is set forward. Upon freeze-drying only a minor part of triolein and nearly no tripalmitin is encapsulated within the matrix. The level of encapsulated triolein decreases when the system is stored at higher a_w's. There is an absolute increase but a relative decrease in the level of encapsulated triolein with increasing initial triolein concentration. Free triglycerides are present as small, thin aggregates on the surface of the freeze-dried matrix or floating on the water film of the hydrated matrix. It is shown that by simple hexane extraction it is possible to distinguish between free and encapsulated lipid. Only free lipid diffuses. Lipid encapsulation and volatiles retention are compared.     

Reduced Fat, High Moisture Beef Frankfurters as Affected by Chopping Temperature

Six treatment combinations were studied to determine the effects of initial temperature (0, 15, 30°C) and endpoint chopping temperatures (0, 15, 30, 45°C) on texture and stability of reduced fat, high moisture beef frankfurters. Textural properties (raw batter, frankfurter) and purge loss were determined over 8 wk storage. As endpoint chopping temperature increased, batter stability and shear force decreased. In most samples, initial temperature did not affect texture or stability. Endpoint chopping temperatures of ± 15°C resulted in most stable batters. Chopping > 15°C lowered product quality.     

Chlorophyll Degradation in a Spinach System at Low and Intermediate Water Activities

Chlorophyll degradation in blanched freeze-dried spinach puree was studied in model systems as a function of water activity (a_w), pH, temperature and also in the presence of glycerol, a water-binding agent. For a_w > 0.32 the most important mechanism of chlorophyll degradation is the transformation into pheophytin. The reaction can occur at very limited water concentration and has a first order dependence on pH, water activity and pigment concentration. The addition of glycerol increases the rate of degradation of chlorophyll. At temperatures higher than 56.7°C and a_w= 0.11, the energy of activation increased, indicating different mechanisms. For temperatures below 38°C the rate tended to increase instead of decreasing with decreasing temperatures because of changes in the sorption isotherm (increase of water content) caused by the shift in the temperature.     

Texture and Storage Stability of Processed Beefsticks as Affected by Glycerol and Moisture Levels

Ground beef-based beefsticks were produced with glycerol levels of 0, 2, and 4%, and dried to water activity levels of 0.90 and 0.85. Samples were analyzed by uniaxial compression and colorimetry after production and after 52°C storage for 1, 2, 3 or 4 wk. Deformability modulus, percent recoverable work, relaxation properties, and relative lightness were calculated. Glycerol, as well as water, acted as an effective textural plasticizer. Reductions in modulus and relaxation parameters due to glycerol addition were in the range of 30–40%. Glycerol can thus effectively be used to adjust physical properties without compromising stability. Higher moisture samples were relatively more elastic, as determined by recoverable work. High temperature storage reduced modulus, solidity and percent recoverable work (20–70%) in all samples.     

Association of Zinc with Soy Proteins as Affected by Heat and pH

The effect of heat on the chemical association of ⁶⁵Zn with proteins and of pH on the solubility of proteins, phytic acid, zinc, and their complex formation were studied in soybeans grown hydroponically and intrinsically labeled with ⁶⁵Zn. ⁶⁵Zn association with soy proteins was not affected by autoclaving. Zinc was not covalently associated with the major soy proteins, 11S and 7S. Protein, phytic acid and zinc content of the raw soyflour was determined at pH range 3.5–12 before and after dialysis. pH had only a slight effect on zinc solubility. Protein-zinc-phytate complex formation was maximum in the pH range 7.5–10.5.     

Kinetics of Corn Meal Gelatinization at High Temperature and Low Moisture

The kinetics of corn meal starch gelatinization and melting was investigated. At 25% moisture, in the temperature range 110–140°C. Arrhenius equation parameters were determined by two calculable procedures which agreed well. Activation energy for gelatinization was calculated to be approximately 86.2 kJ/g-mole. Further experiments in the moisture range 13.4–34.4% and temperature range 10–165°C. yielded results for endotherm enthalpies and melt temperature which agreed with literature reports.     

Gel Properties of Surimi from Various Fish Species as Affected by Moisture Content

Torsion, punch, and color tests as affected by moisture content were evaluated for surimi from pollock, Pacific herring, arrowtooth flounder, and Pacific whiting. Torsion stress and strain decreased linearly with increased moisture content but strain values were less sensitive to moisture than were stress values. This finding enabled mathematical normalization of torsion stress and strain values rather than adjusting the moisture content of samples prior to testing. Punch test results, while linearly related to moisture content, were not as consistent as torsion test results. The L* and whiteness increased with higher moisture content, but changes in a* and b* values were not consistent for surimi from different species.     

Texture and Rehydration of Dehydrated Carrots as Affected by Low Temperature Blanching

Whole carrots were blanched at four temperatures for five time periods, then blanched again for 6 min at 100°C. A control sample was blanched 8 min at 100°C. All samples were then dehydrated. Very slight differences in rehydration ratios between treatments were observed. The 50°C blanch gave a firmness equal to or less than the control for all blanch times. The carrots blanched at 55°C for 15, 30 and 45 min were less firm than the control while the 60 and 90 min blanched samples were firmer than the control. The 60 and 65°C blanched samples had significantly firmer texture than the control when blanch time was > 30 min. Blanching carrots for 45 min at 65°C increased firmness of the rehydrated product by 51% for uncooked and 27% for cooked.