Showing papers in "Journal of Food Science in 1991"
TL;DR: In this paper, dehydrated sugar solutions were used as models of thermal behavior of amorphous foods, and of the effect of temperature, moisture content and time on physical state of such foods.
Abstract: Dehydrated sugar solutions were used as models of thermal behavior of amorphous foods, and of the effect of temperature, moisture content and time on physical state of such foods. The transition temperatures determined were glass transition (Tg), crystallization (Tcr) and melting (Tm) which all decreased with increasing moisture. Tg of a sucrose/ fructose model had a slightly lower value than the empirical “sticky point,” at all moisture contents studied. Crystallization of sucrose was delayed by addition of fructose or starch. Crystallization above Tg was time-dependent, and the relaxation time of this process followed the WLF equation.
626 citations
TL;DR: The effect of chitosan coating (1.0 and 1.5% w/v) in controlling decay of strawberries at 13°C was investigated as compared to a fungicide, iprodione (Rovral®) as discussed by the authors.
Abstract: The effect of chitosan coating (1.0 and 1.5% w/v) in controlling decay of strawberries at 13°C was investigated as compared to a fungicide, iprodione (Rovral®). Chitosan coating significantly reduced decay of berries (P ≤ 0.05) compared to the control. There was no significant difference between chitosan and fungicide treatments up to 21 days storage. Thereafter, Rovral®-treated berries decayed at a higher rate than chitosan-coated berries. Chitosan-coated berries stored at 4°C were firmer, higher in titratable acidity, and synthesized anthocyanin at a slower rate than Rovral®-treated or nontreated berries. Chitosan coating decreased respiration rate of the berries with a greater effect at higher concentration.
488 citations
TL;DR: In this article, the effects of water, freeze-concentration and effective molecular weight on glass transition (T) of maltose and maltodextrins were studied, and methods to predict Tg were used to establish state diagrams.
Abstract: The effects of water, freeze-concentration and effective molecular weight (M,) on glass transition (T,) of maltose and maltodextrins were studied, and methods to predict Tg were used to establish state diagrams. Tg of maximally freeze-concentrated solutes (Tg and onset of ice melting (TJ increased with M,, and for high molecular weight polysaccharides TL and TA were predicted to have the same temperature value. Ice formation at TL
384 citations
TL;DR: Abrasion peeling of carrots results in formation of a white lignin type material on the surface during storage as mentioned in this paper, the degree of its formation was directly related to severity of abrasion during peeling.
Abstract: Abrasion peeling of carrots results in formation of a white lignin type material on the surface during storage. The degree of its formation was directly related to severity of abrasion during peeling. Dipping the peeled product for 30 seconds in a 70°C. Acidic or basic solution (citric acid or sodium hydroxide), retarded formation of the material. The low pH dip did not cause flavor changes.
261 citations
TL;DR: Fresh produce respiration rates (O2 consumption or CO2 evolution) at various O2 and CO2 concentrations, as well as transient and equilibrium gas concentrations within permeable packages, could be accurately predicted with the model equations.
Abstract: A respiration model, based on enzyme kinetics, was proposed for predicting respiration rates of fresh produce as a function of O2 and CO2 concentrations. In this model, the dependence of respiration on O2 was assumed to follow a Michaelis-Menten type equation (r = Vm[O2]/{Km+ [O2]}), and the effect of CO2 on respiration to follow an uncompetitive inhibition model (r = Vm[O2]/{Km + (1 + [CO2]/ Ki) [O2]}). The model predictions agreed well with published data for a variety of commodities and with experimental data for cut broccoli. Fresh produce respiration rates (O2 consumption or CO2 evolution) at various O2 and CO2 concentrations, as well as transient and equilibrium gas concentrations within permeable packages, could be accurately predicted with the model equations.
252 citations
TL;DR: In this article, a piece-size reduction, which is required in preparing lettuce for salads, shortens storage life of cut lettuce as compared to uncut head lettuce, and optimal cold storage was obtained by packaging the cut-lettuce in pouches that had been slightly evacuated and contained a small amount of carbon monoxide.
Abstract: Piece-size reduction, which is required in preparing lettuce for salads, shortens storage life of cut lettuce as compared to uncut head lettuce. Cellular fluids, released during cutting, are removed by rinsing with water, followed by centrifugation to remove added surface moisture. Extended centrifugation can cause desiccation of product, which may be beneficial under certain conditions. Other methods of water removal, such as blotting or forced air did not seem practical. During storage green pigmentation decreased in salad-cut lettuce. Optimum cold storage was obtained by packaging the cut-lettuce in pouches that had been slightly evacuated and contained a small amount of carbon monoxide.
249 citations
TL;DR: Pressurization in ultra-high temperature-processed (UHT) milk and raw milk appeared to provide a protective effect and lessened cell death as compared to pressurizing in phosphate-buffered saline.
Abstract: Listeria monocytogenes Scott A and CA, were subjected at 23°C to hydrostatic pressures ranging from 2,380 to 3,400 atm and Vibrio parahaemolyticus T-3765-1 from 680 to 1,700 atm. For L. monocytogenes Scott A, pressurization in ultra-high temperature-processed (UHT) milk and raw milk appeared to provide a protective effect and lessened cell death as compared to pressurization in phosphate-buffered saline (100 mM, pH 7.0). A population of about 106 CFU/mL L. monocytogenes was killed by exposure to 3,400 atm within 80 min at 23°C in UHT milk. A population of about 106 CFU/mL V. parahaemolyticus was killed by exposure to 1,700 atm within 10 min at 23°C in clam juice.
238 citations
TL;DR: Although Gram-negative bacteria were numerically dominant, a large yeast population was also found and species in the genera Pseudomonas, Erwinia, and Serratia were the most frequently isolated bacteria.
Abstract: Storage of partially processed lettuce resulted in an increase in microbial population, pH, and change in package atmosphere composition (increasing CO2 and decreasing O2). Microbial populations varied in size with variations in processing and packaging. Typical initial log10 counts per g were: bacteria 3.4–5.1, yeasts 2.5–3.2; molds were infrequent. Commercial packaging inhibited bacterial growth and retarded browning. Although Gram-negative bacteria were numerically dominant, a large yeast population was also found. Species in the genera Pseudomonas, Erwinia, and Serratia were the most frequently isolated bacteria. Cryptococcus, Pichia, Torulaspora and Trichosporon spp. were the most common yeasts.
202 citations
TL;DR: In this paper, the authors found that DuoFiber and oat fiber had beneficial effects on properties of low-fat, high added-water bologna, thus providing a way to alter product characteristics.
Abstract: Ingredients incorporated dry into 10% fat and 30% added-water bologna were: DuoFiber®, oat fiber, pea fiber, wheat starch, Firm-tex®, and isolated soy protein. Test bolognas were less firm than the high-fat control but more firm than the low-fat control. Fiber-containing bolognas were more grainy and less juicy than the high-fat control. Low-fat bolognas were darker red than high-fat bologna. DuoFiber and oat fiber had greater cooking losses than the low-fat control, but purge was reduced by all test ingredients, particularly Firm-tex. Lower vacuum level in packages also resulted in less purge. Test ingredients had beneficial effects on properties of low-fat, high added-water bologna, thus providing a way to alter product characteristics.
200 citations
TL;DR: In this article, the effect of phytate hydrolysis by endogenous and exogenous phytases was studied for their effect on increasing iron availability in cereals, including wheat bran and whole meal flours.
Abstract: Phytate (inositol hexaphosphate) hydrolysis by endogenous and exogenous phytases was studied for their effect on increasing iron availability in cereals. Wheat bran and whole meal flours of rye and oats were soaked at optimal conditions for phytase activity (55°C, pH 5) for different time intervals. Phytate and its degradation products were determined by HPLC and related to iron solubility under simulated physiological conditions. Small amounts of phytate (< lμmol/g) had a strong negative effect on iron solubility. When inositol hexa- and pentaphosphates of wheat bran and rye flour were completely hydrolyzed by activating endogenous phytase, iron solubility under simulated physiological conditions increased from 3 to 53% (wheat) and 5 to 21% (rye). Addition of wheat phytase to uncooked oatmeal increased iron solubility from 4 to 11 and in precooked to 18%, while endogenous phytase of uncooked oatmeal had less effect on phytate digestion and iron solubility.
185 citations
TL;DR: Proteins were isolated from chickpea flour by micellization and isoelectric precipitation techniques as mentioned in this paper, and protein content ranged from 84.8-87.8%.
Abstract: Proteins were isolated from chickpea flour by micellization and isoelectric precipitation techniques. Protein content ranged from 84.8-87.8%. Denaturation temperature and transition enthalpy, by differential scanning calorimetry, were higher for micelle than for isoelectric proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a molecular weight distribution between 16.6-66.4 kD for micelle and 14.9-84.2 kD for isoelectric proteins. Most functional properties compared favorably to a commercial soy isolate. In general, most essential amino acids of chickpea isolates were at acceptable levels compared to a reference pattern. High values of in vitro digestibility and calculated PER were obtained for the isolates.
TL;DR: In this paper, three bacterial proteases were selected for their activity on casein per unit cost and conditions for inactivation were determined, and the results suggest fish protein hydrolysates can be used in the food industry for their solubility and nutritional value.
Abstract: Three bacterial proteases were selected for their activity on casein per unit cost. Conditions for inactivation were determined. Fish protein was hydrolyzed without water addition. Protein was solubilized faster with Pescalase 560 than with HT-200 or Protease N. Increase of protease concentration was associated with a quadratic increase in soluble nitrogen. Yields of 13 to 15% in terms of whole fish were obtained at the pilot plant. Products contained 83 to 86% protein of which 70 to 80% was soluble. Reactive lysine was 70 to 85%. Nutritional evaluation with rats indicated hydrolysates had 10 to 15% lower nutritional value than casein. Results suggest fish protein hydrolysates can be used in the food industry for their solubility and nutritional value.
TL;DR: In this article, a trained taste panel, under controlled conditions, perceived slight off-flavor in ‘G3’ strawberries kept in 0.25% or 0% 02.
Abstract: Strawberries (Fragaria ananassa Duch., cv. ‘Selva') were stored 10 days in 1.0%, 0.5%, or 0.25% 02 or air + 20% CO2; or 6 days in air + 50% or 80% CO2 at 0 or 5°C without detrimental effects on quality. Decay and softening were reduced by treatments. An untrained taste panel, under ordinary eating conditions, did not consistently differentiate ‘Pajaro’ strawberries kept in 0.25% 02 from those stored in air. A trained taste panel, under controlled conditions, perceived slight off-flavor in ‘G3’ strawberries kept in 0.25% or 0% 02. This correlated with ethanol, ethyl acetate, and acetaldehyde in juice. The 50% or 80% CO2 treatments caused injury after 8 to 10 days, while 20% CO2 treatments did not. All high CO2 treatments caused increase in pH of juice.
TL;DR: In this article, the anthocyanins in the skin of lychee fruit were isolated and purified by Sephadex G-25 and LH-20 gel column chromatography, and Sep-Pak C-18 cartridge.
Abstract: The anthocyanins in the skin of lychee fruit were isolated and purified by Sephadex G-25 and LH-20 gel column chromatography, and Sep-Pak C-18 cartridge. Further separation by HPLC on a C-18 column, on-line spectra by photodiode array detection, and acid and alkali hydrolyses were used for identification. Cyanidin-3-rutinoside was the major anthocyanin found. Cyanidin-3-gIucoside and malvidin-3-ace-tylglucoside were also identified. Polymerized anthocyanin pigment was also present, appearing to contribute to the brownish-red color.
TL;DR: In this article, a spectrophotometric assay was developed with the specific aim of determining the content in foods of iron-binding phenolic compounds, where foods were extracted with dimethylformamide (50%) and an iron-containing reagent was added.
Abstract: A spectrophotometric assay was developed with the specific aim of determining the content in foods of iron-binding phenolic compounds. Foods were extracted with dimethylformamide (50%) and an ironcontaining reagent was added. The resulting color was due to formation of Fe-galloyl and Fe-catechol complexes. These complexes had different absorbance maxima and could thus be separately determined by readings at two wavelengths. The method was simple and had good precision, accuracy and analytical recovery. The new method was compared with two commonly used methods for determination of phenolic content in cereals, fruits, vegetables, spices and beverages.
TL;DR: In this paper, single strength orange juice was treated with supercritical carbon dioxide (CO2) and the effect of process time, temperature and pressure on pectinesterase (PE) activity was determined.
Abstract: Single strength orange juice was treated with supercritical carbon dioxide (CO2) and the effect of process time, temperature and pressure on pectinesterase (PE) activity was determined. PE could be inactivated with supercritical CO2 below temperatures necessary for thermal inactivation. Higher pressure, temperature and longer treatment time resulted in more inactivation. Inactivation kinetics showed activation energy was significantly reduced at SC CO2 treatment at 31 MPa (97.4 KJ/mole), compared to identical treatments at atmospheric pressure (166.6 KJ/mole). D values ranged from 2673 min at atmospheric pressure and 40 degrees C to 10 min at 31 MPa and 60 degrees C. z value at atmospheric pressure was 8.8 C degrees , and at 31 MPa 5.2 C degrees .
TL;DR: In this article, the authors used both Arrhenius and square root equations to model the growth of Pseudomonas fragi and developed a correlation scheme of P. fragi growth with the TTI response.
Abstract: Time/temperature integrators (TTI) have a potential for monitoring time-temperature history of perishable foods, including dairy products. To correlate the end of shelf life of dairy products with different TTI's, kinetic data for growth of a dairy spoilage microorganism was obtained. Both Arrhenius and square root equations were used to model the growth of Pseudomonas fragi. A significant negative history effect was observed for P. fragi growth rate whereas history effect was positive on the lag phase, under certain nonisothermal conditions. A correlation scheme of P. fragi growth was developed with the TTI response. The application of TTI's for dairy products is feasible despite the history effects.
TL;DR: It was concluded that the human subjects studied had the capacity to absorb COPS from food sources, and the brief residence time of COPS observed in both chylomicrons and plasma suggested rapid transfer of COPs among lipoprotein fractions and/or clearance from plasma.
Abstract: There is no evidence whether humans absorb cholesterol oxidation products (COPS) from food sources. Therefore, (after-meal) absorption of COPS in humans was studied following consumption of a powdered egg meal containing 30–90 ppm each of four different COPS. Both total plasma and plasma chylomicron COPS concentrations increased. By contrast, subjects consuming fresh eggs containing very low levels of the same four COPS (0–2 ppm) demonstrated no significant rise in plasma COPS. We concluded that the human subjects studied had the capacity to absorb COPS from food sources. The brief residence time of COPS observed in both chylomicrons and plasma suggested rapid transfer of COPS among lipoprotein fractions and/or clearance from plasma.
TL;DR: In this article, the degradation kinetics of chlorophylls in spinach puree were studied from 100 to 145°C (2-25 min) and from 80 to 115°C(25-39 min) for chlorophyl compounds, respectively, with an isokinetic temperature of 1608°C.
Abstract: Thermal degradation of chlorophylls and chlorophyllides in spinach puree was studied from 100 to 145°C (2–25 min) for chlorophylls and from 80 to 115°C (25–39 min) for chlorophyllides The derivatives formed were: pheophorbides, pyropheophorbides, pheophytins and pyropheophytins Degradation kinetics of chlorophylls and chlorophyllides followed a first-order kinetic model Reaction rate data showed that the a form of both chlorophylls and chlorophyllides degraded more rapidly than the b form Chlorophyllides were less stable than chlorophylls Activation energies ranged from 150 to 228 Kcal/mol A kinetic compensation effect was observed for both chlorophylls and chlorophyllides with an isokinetic temperature of 1608°C The relative stability of these compounds suggests that methods to maximize chlorophyllides would not be effective for improving green color stability
TL;DR: The use of charcoal with palladium chloride, as ethylene absorbent, prevented the accumulation of the ethylene and was effective in reducing the rate of softening in kiwifruits and bananas and of chlorophyll loss in spinach leaves as mentioned in this paper.
Abstract: Ethylene had an undesirable effect on the quality of kiwifruits, bananas, broccoli, and spinach leaves that were prepared and stored as lightly processed products. A 2.or 20 ppm ethylene treatment hastened the softening of the pulp of kiwifruits and bananas held at 20°C. Use of charcoal with palladium chloride, as ethylene absorbent, prevented the accumulation of the ethylene and was effective in reducing the rate of softening in kiwifruits and bananas and of chlorophyll loss in spinach leaves, but not in broccoli.
TL;DR: In this paper, the microstructure of hen egg granules was investigated and it was shown that the granules consisted of three proteins (low-density lipoprotein, lipovitellin and phosvitin).
Abstract: We investigated the microstructure of hen egg granules. Polyacrylamide gel electrophoresis revealed that the granules consisted of three proteins (low-density lipoprotein, lipovitellin and phosvitin). Atomic absorption spectrometry revealed a notable amount of divalent and trivalent cations. Scanning electron microscopy showed that pH modifications induced the loss of granule structure by solubilization of proteins. Similar observations were made when ionic strength was increased by addition of sodium chloride. All results were indicative of the. existence of phosphocalcic bridges between phosphate groups of the three proteins.
TL;DR: In this paper, the effects of various levels of sodium lactate on selected physical, sensory, and microbiological characteristics of fresh pork sausage stored at 4°C for 28 days were evaluated.
Abstract: The objective of our study was to evaluate the effects of various levels (0%, 1%, 2%, 3%) of sodium lactate on selected physical, sensory, and microbiological characteristics of fresh pork sausage stored at 4°C for 28 days. Samples containing 0% and 1% SL reached 108 CFU/g after 10 days refrigerated storage. Addition of 2% or 3% SL to fresh pork sausage delayed microbial deterioration, pH decline, and development of sour- and off-flavors 7 days at 4°C. Samples containing 2% SL did not reach total plate counts of 108 CFU/g until 24 days storage. SL appeared to protect red color, and to “enhance” pork-and salty-flavors in sausage. TBA, L-, a-, and b-values were unaffected by SL level.
TL;DR: In this paper, the initial microbial population in shredded iceberg lettuce (Lactuca sativa L.) cv 'Great Lakes', and their changes under different controlled atmospheres, were determined.
Abstract: Our purpose was to determine initial microbial population in shredded Iceberg lettuce (Lactuca sativa L.) cv 'Great Lakes', and to study their changes under different controlled atmospheres. Lettuce was shredded, washed, disinfected, water rinsed and centrifuged before being stored for 12 days under air, 3% O2, 3% O2 + 5% CO2 or 3% O2 + 10% CO2. of visual Microbiological analysis and assessment of visual quality were carried out every 3 days. No human pathogens were found. Controlled atmospheres had little or no effect on the microbiological populations studied. A 3% O2 + 10% CO2 atmosphere maintained acceptable visual quality of lettuce, without appreciably affecting microbial development.
TL;DR: In this paper, the microbial shelf-life of Roast beef with up to 3 or 4% sodium lactate was investigated and the results showed that the microflora consisted primarily of Micrococcus and coagulase-negative Staphylococcus spp.
Abstract: Cooked, vacuum packaged beef top rounds injected with 0, 1, 2, 3 or 4% sodium lactate were stored up to 84 days at 0°C. Aerobic plate counts (APC), water activity, pH and lactic acid content were determined at 14-day intervals. Microbial distributions were characterized following 0.56 and 84 days storage. Increasing sodium lactate resulted in reduction in APC. Water activity was not affected by sodium lactate level. Decreases in pH were minimized at sodium lactate >3%. Initially, the microflora of roasts consisted primarily of Micrococcus and coagulase-negative Staphylococcus spp. After 84 days the microflora consisted primarily of hetero- and homofermentative Lactobacillus spp. No differences in APC, lactic acid content, pH or water activity occurred between top rounds with 3 and 4% sodium lactate. Cooked, refrigerated roast beef injected with up to 3 or 4% sodium lactate had microbial shelf-life up to 84 days.
TL;DR: In this paper, the glass transition temperature of dry amorphous sucrose at 57°C was decreased to -46°C as the sucrose was plasticized with excess water.
Abstract: Amorphous sucrose showed typical thermal transitions of amorphous materials. The temperatures of those transitions, glass transition, crystallization and melting, decreased with increasing moisture content. The glass transition temperature of dry amorphous sucrose at 57°C was decreased to -46°C as the sucrose was plasticized with excess water. That value remained constant due to maximal freeze-concentration with 72-73% sucrose in the unfrozen matrix which showed ice melting at -34°C. Concentrated solutions may become supercooled resulting in partial freeze-concentration with resultant lowering of glass transition temperature.
TL;DR: In this paper, the qualities of beef cuts were compared with near-infrared (NIR) spectroscopy readings using reflectance, transmittance and a fiber optic probe.
Abstract: The qualities of beef cuts were compared with near-infrared (NIR) spectroscopy readings using reflectance, transmittance and a fiber optic probe. Multiple linear regression analyses were used to select the optimum wavelengths for estimating beef properties. High multiple correlation coefficients (R) were obtained for Warner-Bratzler shear value (R = 0.798−0.826), protein (R = 0.822−0.904), moisture (R = 0.895−0.941), fat (R = 0.890−0.965) and energy content (R = 0.899−0.961) with each reflectance, transmittance and using the fiber optic probe. Total pigment content also highly correlated with optical densities using transmittance (R = 0.946) and the fiber optic probe (R = 0.893). NIR with a fiber optic probe is a useful tool for determining physical and chemical characteristics of beef.
TL;DR: In this paper, a simple rapid isocratic HPLC method was used to separate sugar and organic acids on an Aminex HPX-87 column in the H+ form and detected using ultraviolet and refractive index detectors in series.
Abstract: In a simple, rapid isocratic HPLC method sugars and organic acids were separated on an Aminex HPX-87 column in the H+ form and detected using ultraviolet and refractive index detectors in series. Sugars (lactose, glucose and galactose) and acids (orotic, citric, pyruvic, lactic, uric, formic, acetic, propionic, butyric and hippuric) were identified by retention times. This method affords a simple technique for monitoring starter culture activity and following quality changes during cheese maturation.
TL;DR: In this paper, aseptically processed and packaged spinach puree was processed at four time-temperature treatments (19.2 and 5.3 sec at 142°C, 19.2 sec at 137°C and 19.3sec at 19.5 sec at 136°C) and showed that chlorophyll b degradation and pheophytin b formation during storage in flexible containers at 4, 25, and 40°C fit a first order kinetic model.
Abstract: Spinach puree was aseptically processed and packaged at four time-temperature treatments (19.2 and 5.3 sec @ 142°C; 19.2 and 12.2 sec @ 137°C). Samples processed at 142°C for 5.3 sec retained 68% of total chlorophyll compared to blanched samples while all chlorophylls were degraded in retorted product. The rate of chlorophyll b degradation and pheophytin b formation during storage in flexible containers at 4, 25, and 40°C fit a first order kinetic model. Apparent activation energies during storage for each time-temperature treatment ranged between 11.1 and 14.3 kcal/mol. Analyses of degradation products indicated oxidation during storage was not a dominant factor in chlorophyll conversion and color loss.
TL;DR: In this article, a vacuum packaged beef top round was injected with 0, 1, 2, 3 or 4% sodium lactate and stored for up to 84 days at 0°C.
Abstract: Cooked, vacuum packaged beef top rounds injected with 0, 1, 2, 3 or 4% sodium lactate were stored up to 84 days at 0°C. Cooking yields and chemical composition were determined initially, while changes in sensory attributes, Warner-Bratzler shear force and color were evaluated after 0, 14, 28, 42, 56, 70 and 84 days storage. Increasing sodium lactate resulted in higher cooking yields and darker, redder color with less gray surface area. Flavor notes associated with fresh beef were enhanced by addition of sodium lactate, and flavor deterioration during storage was minimized. Palatability was improved by adding 1% sodium lactate, but beyond 1 to 2% it did not further improve. Changes in cooked meat tenderness were verified by Warner-Bratzler shear force measurements.
TL;DR: In this article, the retrogradation process of rice starch gels is a function of time and the enthalpy for rice starch gel with high amylose content was higher than those for low amyloses content or for waxy starch samples.
Abstract: In waxy and nonwaxy rice starch gels the retrogradation process was a function of time. The enthalpy for rice starch gel with high amylose content was higher than those for low amylose content or for waxy starch samples. In all rice starch gels, samples stored under 25°C had lower enthalpy and higher endothermic onset temperature. In presence of sucrose, extent of retrogradation increased, while in presence of NaCl, it decreased. Effects of maltose, glucose and lipids were dependent on rice starch gel and storage temperature.