Showing papers in "Journal of Food Process Engineering in 1977"

Prediction of freezing times for foods as influenced by product properties

Abstract: This investigation utilizes a computer simulation technique to predict the freezing times and temperature history curves for food products. The input information consists of the product properties for temperatures above the initial freezing point, freezing medium conditions and the initial product temperature. It has been established that food products with lower initial freezing points, higher initial water contents and higher initial product densities will have longer freezing times. The prediction of freezing time is most sensitive to the accuracy of the measurement of the product density and the initial freezing point if the freezing point is above −0.5°C. The influence of the accuracy of unfrozen product thermal conductivity data on the freezing time is not important in the range of 0.45 to 0.55 W/m°K investigated. The combined influence of inaccuracy in measuring these product properties on the freezing time prediction will be significant even if the influence of an individual product property is small.

Mass transfer characteristics of hollow fiber ultrafiltration of soy protein systems

Abstract: Mass transfer characteristics and the applicability of theoretical transport models in ultrafilitration were evaluated in a pilot-scale hollow fiber system processing soybean water extracts. Permeate flux was found to increase linearly with transmembrane pressure and then reach an asymptotic value. Substantial deviations from the pure water permeation line and marked hysteresis effects were also observed, indicative of concentration polarization and additional hydrodynamic resistance at the membrane surface. Pressure-independence occurred at lower pressures with lower Reynolds Numbers (Re) and higher Schmidt Numbers (Sc). Flow rate and temperature significantly affected flux in the totally polarized region. The exponent in the flux-Reα relationship varied from 0.6 at 20°C to 0.32 at 50°C. Theoretical laminar flow mass transfer models were found to predict Sherwood Numbers (Sh) and flux lower than experimental values. The correlation that fit the data best was Sh = 0.181 (Re).47 (Sc).33

Energy consumption for refrigerated, canned, and frozen peas

Abstract: The energy inputs at different stages in the total food cycle of peas were estimated for the market modes: refrigerated, frozen, and canned. The energy accounting showed for refrigerated 3,368; for canned 3,637; and for frozen 3,281 Btu/2.8-oz serving. Because the energy consumption for each market mode is of the same order of magnitude, there is little reason for the consumer to select on bases other than availability, taste preference, and convenience. It was also found that energy for packaging, marketing, shopping, and in the home can be high depending on the market mode. Measures to reduce energy consumption are discussed for several sectors.

Moisture adsorption influences on rice

Abstract: Rice is a hygroscopic grain which adsorbs or desorbs moisture depending on its ambient environment. Moisture desorption is associated with rice drying. Much research has been conducted to determine those drying procedures which produce the highest head rice yield. Moisture adsorption is associated with water reentering the rice grain. This occurs when the vapor pressure within the grain is lower than the vapor pressure in the surrounding air. Rapid moisture readsorption causes the rice grain to fissure. Fissured grains usually break during subsequent hulling and milling operations. This paper reviews the literature related to moisture adsorption and fissuring of the rice grain, and discusses those preharvest and postharvest conditions where rice grains are subjected to moisture-adsorbing environments which have the potential to fissure the grain and subsequently reduce head rice yield.

Effluent generation, energy use and cost of blanching

Abstract: Blanching and cooling of vegetables is a major source of wastewater in the vegetable processing industry. In recent years modification of conventional blancher designs have been developed. Using material and heat balances, the theoretical effluent generation and energy use of blanching and cooling can be calculated. Actual performance of blanchers can then be compared to these theoretical quantities. The Vibratory Blancher-Cooler, the Hot-Gas Blancher and the Hydrostatic Steam Blancher are new blancher designs that have been developed in recent years. The effluent generation and energy use of these new designs as compared to conventional steam and water blanchers can be determined from published reports. When the operating costs of the above modifications are compared to those of a conventional water blancher, the low capital cost of the water blancher makes it the most economical choice. However, a doubling of the combined cost of energy, water and wastewater disposal would give the Vibratory Spiral Blancher-Cooler an operating cost equivalent to that of a water blancher and flume cooler.

Processing whey-type by-product liquids from cottonseed protein isolation with ultrafiltration and reverse osmosis membranes

Abstract: Cottonseed wheys resulting from protein isolation from cottonseed flour were processed by semi-permeable ultrafiltration (UF) and reverse osmosis (RO) membranes. The UF membrane fractionated the soluble whey constituents by retaining protein and passing through salts, carbohydrates and other non-protein components along with most of the water. The UF membrane effluent was then processed through an RO membrane to recover a secondary product containing the whey materials not retained in the protein product from the UF membrane. The feasibility of recycling effluent from the RO membrane for reuse in subsequent protein extractions was demonstrated. Thus, the threat of water pollution from effluent disposal could be eliminated completely and process water requirements drastically reduced. Spray-dried UF protein concentrates were tested for utilization in protein fortification of breads and noncarbonated beverages and as whipping products. They exhibited commercial potential for use in these food applications. The economics of processing the whey-type liquids by the membrane process under investigation were analyzed. Membrane processing of wheys by each of two alternative whey processing systems proved to be economically attractive.

Analysis and economic evaluation of concentration alternatives for liquid foods — quality aspects and costs of concentration

Abstract: In the selection of concentration processes the net added value of the concentrate with respect to the capital invested should be maximized. The net added value expressed per unit weight of feed is the difference between the gross added valve, being the increase in product value due to concentration, and the costs of concentration. The main factors affecting the gross added value and the concentration costs are treated systematically. The main factors influencing the gross added value are: thermal quality degradation by chemical reactions; loss of volatile aromas; and the concentration that is obtained in the process. The first two factors generally affect the gross added value negatively. The thermal effects of the various processes are shortly summarized. In revaporative concentration and reverse osmosis, aromas can usually be recovered by steam stripping and distillation if the aromas in the food are at least a factor of three more volatile than water. For liquids containing aromas with a relative volatility close to or smaller than unity only freeze concentration can be used, if the quality is to be fully retained. The approximate costs of concentration are given for dewatering capacities in the range of 1 to 50 tons per hour and 2000 to 7000 operational hr per year. As energy costs increase further, only concentration processes with a relatively low energy consumption will, at least for higher capacities, remain economically justified. The energy consumptions expressed in steam equivalents vary widely, viz. evaporation 0.16–1.3, freeze concentration 0.25–0.5, and membrane processes 0.01–0.48.

Heat and mass transfer fundamentals applied to food engineering1

Abstract: There is a need for deeper qualitative and quantitative understanding of the heat and mass transfer mechanisms underlying various techniques for food production, processing, preservation and storage. This is important for the development of new food sources, for more economical and energy-efficient processing of food from existing sources, for better food quality and quality control, and for adherence to new regulations such as nutritional labeling and shelf-life dating. Several classes of food-processing problems are presented where advances can be made on the basis of improved understanding of heat and mass transfer mechanisms. These include cases of competing transport, cases where transport competes with kinetics of chemical or biochemical reactions, and cases where determination and understanding of the rate-determining factor are needed. Specific examples are drawn from drying processes, leaching and extraction, freezing, sterilization and enzyme deactivation, and artificial cultivation.

SIMULATION OF AN IMMOBILIZED ENZYME PARTICLE USING β‐GALACTOSIDASE ADSORBED TO A PHENOL‐FORMALDEHYDE RESIN

Abstract: The mass transfer and kinetic properties of both soluble and immobilized β-galactosidase were investigated. A reversible enzyme kinetic model was found to best fit the soluble and immobilized enzymatic lactose hydrolysis. A finite difference model was used to simulate the steady state and unsteady state behavior of an immobilized enzyme particle. The performance of the catalyst in a stirred tank reactor was simulated by using the physical properties of the support with the kinetic model and varying the effective substrate diffusivity to fit the data. A sensitivity analysis was performed to evaluate the effect of particle size, diffusivity, external mass transfer coefficient and enzyme loading.

Effect of temperature and water concentration during processing on food quality

Abstract: Water content and temperature during food processing have a pronounced influence on the rates of those changes in food properties which are the object of the process such as reduction in water content or sterilization. However, they also strongly influence adverse side effects such as browning, loss of nutrients or shrinking. When the effects of temperature and water concentration on the process rates of the desired and adverse processes are known, the processes can be optimized. An example of the optimization procedure is given for the spray drying of heat-labile aroma containing liquid foods. Both temperature and moisture content of the droplets change with time in spray-drying. In a second example a new and simple calculation method is introduced for the optimization of quality retention in the sterilization of packed foods.

COMPACTION BEHAVIOR OF BULK WHOLE CORN KERNEL AT PRESSURES UP TO 34.6 MN/m2

Abstract: The compaction behavior of whole corn kernel (1.8–22.0% mc, w. b.) was investigated by axial compression in an 18.5 mm diameter die using the Amatek Universal Testing Machine at 28°C. The maximum applied pressure in each experiment was 34.6 MN/m2 at loading rates of 0.028, 0.28, and 2.8 mm/s. Sample failure due to oil expression or sample extrusion did not occur in any test run. However, extensive physical rupture of corn kernels occurred at 1.8% moisture content and at lesser but significant levels at 6.6 and 9.7% moisture. At 15.9 and 22.0% moisture, samples were plastically deformed but little macroscopic kernel damage was evident. The effectiveness of compaction increased dramatically as moisture content increased up to 22.0% and then appeared to gradually decline with further increase in moisture. The average compression ratio at zero pressure varied from an average low of 1.70 at 1.8% to an average high of 1.92 at 22.0% mc corresponding to reductions in corn volume of 41 and 47%, respectively. In contrast, loading rate had little effect on density-pressure profiles. The latter were not adequately characterized by powder compaction models reported in the literature. Substantial volumes of internal tissue gas were estimated with an average maximum of 21% in 15.9% moisture corn kernels. The extent of stress relaxation after termination of compaction increased as loading rate increased and was highest in 15.9% moisture corn. The pressures required for the ejection of compacted corn from the 18.5 mm die varied from 0.5 to 2.1 MN/m2 and revealed an average maximum value at 9.7% moisture. Ejection pressures were substantially independent of loading rate. The most stable compacted corn samples were those produced at the 15.9% moisture level although the compact stability in general was very poor indeed.

Firmness and thermal conductivity of red beets in storage

Abstract: Firmness and thermal conductivity of “Detroit Dark Red, Ferry's Strain” and “Ruby Queen” beets were determined after storage at: 0°C, 95% relative humidity (RH); 12.8°C, 24% RH, and 1.7°C, uncontrolled humidity. Firmness at fixed temperature and humidity conditions decreased with storage; it could be described by a first order rate equation. At a fixed temperature (1.7°C) and uncontrolled humidity, magnitudes of firmness varied as the humidity varied; in contrast, thermal conductivity was influenced very little. At 0°C and 95% rel. humidity, thermal conductivity remained essentially constant for four weeks. The magnitude of thermal conductivity, at room temperature and on the day of harvest, was about the same for four different varieties of beets; “King Red,”“Detroit Dark Red, Ferry's Strain,”“Ruby Queen,” and “Detroit Dark Red, Morse's Strain;” it ranged between 0.579 and 0.600 W/m °K.

Effect of storage and processing conditions on sorghum kernel strength

Abstract: Compressive strength of sorghum kernels was measured to determine the effect of storage conditions on processing for animal feed. Ensiling grain affected a larger decrease in kernel compressive strength than did storage at a high moisture level. Results similar to the above were noted for tests conducted on kernels obtained from animal feces. Microscopic examination of kernels from each treatment revealed greater removal of kernel structure for those of lower compressive strength.

Energy inputs for production, packaging and transportation of wine

Abstract: Energy expenditure for wine during its processing, packaging, and transportation was studied; the study was based on data from a winery in upstate New York for the years 1974–75 and 1975–76. It was found that the following quantities of energy are expended in each of the studied segments per case of twelve 1/5 gal. bottles: winery operation— 6.10 × 104Btu; ingredients and processing aids— 1.34 × 104Btu; packaging materials— 1.76 × 105Btu; and transportation for distribution— 2.78 × 104 Btu. All four segments should be studied for their potential for energy conservation.

Laboratory evaluation of paperboard cartons for the nonrefrigerated storage of sterilized milk1,2

Abstract: The suitability of various carton materials for the nonrefrigerated storage of sterilized milk was investigated. One quart paperboard cartons were fabricated from the same base sheet of stock but varied in the type of sizing used to make them resistant to penetration by liquids and whether or not they were aluminum foil-lined. They were preformed and sterilized with ethylene oxide. The four types of paperboard were: (a) rosin (sizing) paperboard (R); (b) rosin paperboard with foil lining (RF); (c) cyanasize (sizing) juice paperboard (CJ); and (d) cyanasizejuice paperboard with foil lining (CJF). Each carton was aseptically filled and sealed, in a glovebox. Incubation was carried out at 20°C for up to nine weeks. Every week five cartons of each type were randomly selected and the milk tested for microbial stability and flavor. The candidate cartons were also tested for degradation of the physical characteristics of static bulge, wicking, tensile strength, and stiffness. Of these, it appears as if selection of carton type will be determined mostly by wicking resistance. The most acceptable carton type is CJF, which had minimal wicking, acceptable bulge, acceptable stiffness, and acceptable tensile strength during the testing period.