Showing papers in "Journal of Food Science in 1998"
TL;DR: In this paper, the rheological characterization of stirred yogurt with added milk fat, Na caseinate (or micellar casein) and gelatin (4 Bloom strengths), starch or a xanthan gum/LBG 50:50 mixture was carried out.
Abstract: The rheological characterization of stirred yogurt with added milk fat, Na caseinate (or micellar casein) and gelatin (4 Bloom strengths), starch or a xanthan gum/LBG 50:50 mixture was carried out. Dynamic and shear values were measured at 8°C and syneresis at 4°C. Consistency (k* and k) and syneresis were more frequently influenced by the composition variables than the power law factors n* and n and the critical strain γc. The k* ranged from 15.8 to 576 Pa sn*, n* from 0.038 to 0.220, γc from 1.6 to 49.0 10-3, k from 0.37 to 32.47 Pa sn, n from 0.005 to 0.587, and syneresis from 0.0 to 49.2%.
282 citations
TL;DR: In this paper, high pressure pretreatment was applied to apples to increase mass transfer rates during osmotic dehydration of pineapples and accelerate the rehydration process, and the increase in cell wall break-up was attributed to breaking-up of cells walls.
Abstract: High pressure pretreatment (100–700 MPa) was applied to
enhance mass transfer rates during osmotic dehydration of
pineapples and accelerate the process. Experimentally determined
diffusivity values, based on a Fickian model, increased
fourfold for water and twofold for sugar. Diffusivity
values were correlated with pretreatment pressure by an
equation of the form D�A exp(�B/P), which suggests that
diffusivity would level after an initial increase in pressure.
The increase was attributed to breaking-up of cells walls
which facilitated the transport of water. Evidence for the extent
of cell wall break-up with applied pressure was based
on differential interference contrast microscopic examination
of tissue. Preliminary experiments on rehydration characteristics
showed high pressure pretreated samples did not
absorb as much water as controls.
205 citations
TL;DR: In this paper, the surface structure of spray-dried microcapsules with wall systems consisting of mixtures of whey protein isolate (WPI) and maltodextrins (DE 5, 10, 15) or corn syrup solids (DE 24).
Abstract: Microstructure was studied on spray-dried microcapsules with wall systems consisting of mixtures of whey protein isolate (WPI) and maltodextrins (DE 5, 10, 15) or corn syrup solids (DE 24). Structure of microcapsules was appreciably affected by type of carbohydrate and by the WPI-to-carbohydrate ratio. The extent of surface indentation was inversely related to the proportion of WPI in the wall system. Ratio of low-to-high molecular weight solutes in the wall system affected structure. At a WPI-to-carbohydrate ratio of 1:1 or higher, whey proteins improved the surface-smoothness and decrease surface indentation of maltodextrin-based microcapsules. Combinations of WPI with high-DE value carbohydrates were more effective than those with carbohydrates of low DE value in limiting surface-dents formation.
186 citations
TL;DR: In this paper, the authors evaluated the anthocyanin composition of red potatoes (Solanum tuberosum and S. stenotomum) and found that the levels of monomeric and monochromatic anthocalin content ranged from 2 to 40 mg/100g tuber fresh weight.
Abstract: Red potatoes (Solanum tuberosum and S. stenotomum) were evaluated as potential sources for natural red colorants. Qualitative anthocyanin composition, pigment content and phenolic composition were screened on 33 cultivars. Monomeric anthocyanin content, determined by pH differential, ranged from 2 to 40 mg/100g tuber fresh weight. Two breeding clones, NDOP5847-1 and NDC4069-4, showed anthocyanin content >35 mg/100g. Anthocyanin composition was characterized by HPLC, spectral analyses and mass spectroscopy (MS). All red potato samples showed similar pigment profiles, with pelargonidin-3-rutinoside-5-glucoside acylated with p-coumaric acid being the major anthocyanin (ca 70%). Anthocyanin content and profiles of epidermal tissue and flesh were compared for NDC4069-4. The presence of glycoalkaloids in color extracts was detected by MS. Some red-fleshed potatoes may be good potential sources of food colorants.
173 citations
TL;DR: In this paper, the authors measured the progression of lipid oxidation after cooking and found that preventing oxygen exposure after cooking was more important for cooked meat quality than packaging, irradiation, or storage conditions of raw meat.
Abstract: Raw-meat patties were prepared from three pork muscles, irradiated in different packaging environments, and stored for 0 or 3 days before cooking. Lipid oxidation by-products were formed in the raw meat during storage and the baseline lipid oxidation data of raw meat was used to measure the progression of lipid oxidation after cooking. Thiobarbituric acid-reactive substances (TBARS) and volatiles data indicated that preventing oxygen exposure after cooking was more important for cooked meat quality than packaging, irradiation, or storage conditions of raw meat. Propanal, pentanal, hexanal, 1 -pentanol, and total volatiles correlated highly (P < 0.01) with TBARS values of cooked meat. Hexanal and total volatiles represented the lipid oxidation status better than any other individual volatile components.
140 citations
TL;DR: Transglutaminase has been shown to improve the crumb strength of baked loaves and reduce the required work input and substantially improved the water absorption of the dough as mentioned in this paper.
Abstract: Microbial transglutaminase forms nondisulfide covalent crosslinks in proteins and is being used in foods. This enzyme may produce beneficial effects during breadmaking that are comparable to traditional oxidizing improvers, hypothesized to act via formation of disulfide crosslinks. Transglutaminase greatly improved the crumb strength of baked loaves and provides a potential solution to a common consumer complaint. Transglutaminase also reduced the required work input and substantially improved the water absorption of the dough. Each of these effects would lower processing costs for commercial baking.
137 citations
TL;DR: In this paper, the effect of water activity (a w ) on heat resistance of Bacillus cereus spores (decimal reduction time) was investigated and a linear relationship was found between log D and 1-a w.
Abstract: Initially, the effect of water activity (a w ) on heat resistance of Bacillus cereus spores (decimal reduction time) was investigated. A linear relationship was found between log D and 1-a w . The combined effects of temperature (85-105°C), pH (4.56.5) and water activity (0.80-1) were then studied. A four parameter model was fitted to the data. This model appeared to be parsimonious with each parameter having a biological significance. Interactions between factors were observed but they accounted for <2.4% of the total variation and they were not taken into account by the model.
136 citations
TL;DR: EMG was useful for comparing mastication of different groups of panelists and appeared to be an interesting alternative for information about texture perception of naive subjects.
Abstract: Electromyography recordings (EMG) were performed on 10 naive and 10 trained subjects during mastication of different samples of beef. For each group of subjects, ordinary mastication was compared to mastication accompanied by tenderness assessment of the chewed sample. Trained subjects showed a larger variation in muscle work than a naive group when chewing. Sensory assessment modified more the mastication profiles of trained subjects than those of naive ones and these variations occurred at the beginning of the masticatory sequence. EMG was useful for comparing mastication of different groups of panelists and appeared to be an interesting alternative for information about texture perception of naive subjects.
135 citations
TL;DR: The light-induced off-flavor and dimethyl disulfide increased as fluorescent light exposure increased from 0,2,4,6, to 8h (P<0.05).
Abstract: The light-induced off-flavor and dimethyl disulfide increased as fluorescent light exposure increased from 0,2,4,6, to 8h (P<0.05). Sensory evaluation and identified compounds suggest that dimethyl disulfide was mainly responsible for the light-induced off-flavor in skim milk. Dimethyl disulfide was formed by the singlet oxygen oxidation of methionine in milk. Gas chromatographic analysis and sensory evaluation showed that 200, 500, and 1000 ppm ascorbic acid, which is a singlet oxygen quencher, lowered the formation of dimethyl disulfide and off-flavor in skim milk (P<0.05).
129 citations
TL;DR: In this paper, the feasibility of immobilizing naringinase in a food contact approved packaging film was evaluated and it was shown that the naredinase had an optimum pH of 3.5 and a pH of 4.0 at 7°C.
Abstract: Naringin, a bitter compound in citrus, may be converted to a nonbitter form by enzymic hydrolysis. Our objective was to determine the feasibility of immobilizing naringinase in a food contact approved packaging film. Naringinase from Penicillium sp. was immobilized in cellulose acetate films with up to 23% efficiency at 7°C. Kinetic studies showed that the free enzyme had an optimum pH=3.5 and the immobilized enzyme pH=4.0. Activation energy decreased upon immobilization (from 14.2 to 11.0 Kcal/mol) thus providing an increased catalytic efficiency for immobilized naringinase. The Michaelis constant for immobilized naringinase (K m =2.1 mM) was lower than for free enzyme (K m =3.6 mM). Keeping films under dry storage for 1 moat room temperature did not cause decreased enzyme activity. A film area/volume ratio (cm 2 /mL of 10° Brix grapefruit juice) of 7.2 hydrolyzed 60% of the naringin in 15 days at 7°C.
125 citations
TL;DR: In this paper, Pinto bean meals with 18, 20, and 22% moisture were extruded at 140,160 and 180°C, using screw speeds of 150,200 and 250 rpm in a single-screw laboratory extruded.
Abstract: Pinto bean meals with 18, 20, and 22% moisture were extruded at 140,160 and 180°C, using screw speeds of 150,200 and 250 rpm in a single-screw laboratory extruded. Expansion index, bulk density, water absorption and solubility indices, in vitro protein digestibility, and trypsin inhibitor activity in extrudate were measured. Temperature and feed moisture influenced (p<0.05) expansion index, bulk density, water absorption index and in vitro protein digestibility. Water solubility index was affected by temperature only. Trypsin inhibitors were inactivated completely for all conditions. Screw speed had no effect on any dependent variable. Best product was produced with 22% feed moisture at 160°C.
TL;DR: In this article, the effects of slicing method on the quality and storage-life of modified atmosphere packaged carrot slices were determined using microscopy, sensory evaluation, microbial counts and a range of physical and chemical tests.
Abstract: The effects of slicing method on the quality and storage-life of modified atmosphere packaged carrot slices were determined using microscopy, sensory evaluation, microbial counts and a range of physical and chemical tests. Slicing caused physical damage, physiological stress and enhanced microbial growth. The severity of these effects were in the order of blunt machine blade > sharp machine blade > razor blade. These findings provide insights into the magnitude and basis of slicing effects and also confirm the importance of gentle processing and the use of a sharp blade.
TL;DR: In this paper, the changes that cauliflower and spinach leaves undergo after treatment with high hydrostatic pressure were analyzed using a scanning electron microscopy (SEM) technique. And the ultrastructure showed that parenchyma organization disappeared in spinach leaf and cavity formation occurred after treatment, while cauliflower exhibited a firm structure with a soaked appearance.
Abstract: Cryo-fracture scanning electron microscopy revealed the changes that cauliflower and spinach leaves undergo after treatment with high hydrostatic pressure. High pressure changed cell permeability and enabled movement of water and metabolites from inside to outside of the cell. The ultrastructure showed that parenchyma organization disappeared in spinach leaf and cavity formation occurred after treatment. However, cauliflower exhibited a firm structure with a soaked appearance and would be more suitable than spinach for high hydrostatic pressure treatment.
TL;DR: In this article, pressure stability of polyphenoloxidases (PPO) from apples, avocados, grapes, pears and plums was determined at pH 6-7.
Abstract: Pressure stabilities of polyphenoloxidases (PPO) from apples, avocados, grapes, pears and plums were determined at pH 6-7. These PPOs differed in pressure stability, but all were rather pressure-stable. Inactivation of PPO from apple, grape, avocado and pear at room temperature (25°C) became noticeable at 600, 700, 800 and 900 MPa respectively, and followed first-order kinetics. Plum PPO was not inactivated at room temperature by pressures up to 900 MPa. For the two most pressure-stable PPOs, we investigated whether pressure stability would be reduced by the simultaneous application of mild heat. In case of plum PPO, activity reduction was detectable at 900 MPa and 50°C. Further temperature increase resulted in increase of the inactivation rate constant (E a 63 kJ/mol). In case of pear PPO, temperature increase up to 35°C resulted in a 3-fold reduction of the inactivation rate constant. Only at higher temperatures, increase of the inactivation rate constant with increasing temperature was noted (E a 120 kJ/mol).
TL;DR: Results suggest probiotic lactic acid bacteria could be effectively utilized for meat fermentation to produce healthy meat products.
Abstract: Lactobacillus acidophilus group bacteria (L. acidophilus, L crispatus, L. amylovorus, L. gallinarum, L. gasseri, L. johnsonii), probiotic lactic acid bacteria, were applied to meat fermentation. Of six strains, L. gasseri (predominant lacto-bacilli in human intestinal tracts) JCM1131T exhibited greatest fermentation performance in meats. This strain resisted gastric acid and bile, and would thus have no detrimental effects in the intestinal tract. Inoculation of the strain depressed the propagation of S. aureus cells and their enterotoxin production during meat fermentation. Results suggest probiotic lactic acid bacteria could be effectively utilized for meat fermentation to produce healthy meat products.
TL;DR: Phytate is recommended over carnosine as an effective antioxidant in cooked meats because it inhibited metmyoglobin formation in raw samples during storage and inhibited lipid peroxidation in cooked beef.
Abstract: Antioxidant and color stability effects of carnosine and phytate were compared in a fresh beef model system and in cooked beef. Both compounds increased the rate of pH decline in pre-rigor muscle. Phytate also increased the rate of post-mortem glycogen catabolism. Both antioxidants inhibited metmyoglobin formation in raw samples during storage. Phytate was more effective than carnosine for inhibition of lipid peroxidation. Heme iron content was negatively related to lipid peroxidation in cooked beef (r=-0.92). Phytate was also more effective for inhibition of iron release from heme during cooking. Phytate is recommended over carnosine as an effective antioxidant in cooked meats.
TL;DR: In this paper, the use of vacuum impregnation to introduce cryopreservatives into the fruits was tested and the results showed that compositional, mechanical and structural properties improved as a result of the vacuum impregnation.
Abstract: Freezing ensures the longterm preservation of fruits, but usually destroys cell compartmentation of fruit tissues, thereby increasing the probability of undesirable reactions. The use of cryoprotectants/cryostabilizers may reduce ice crystal damage by modifying the glass transition of frozen fruit or reducing freezable water content. The use of vacuum impregnation to introduce cryopreservatives into the fruits was tested. Apple samples were vacuum impregnated with concentrated grape musts and pectin solutions, by applying vacuum (50 mbars) for 5 min and afterwards restoring atmospheric pressure while fruit remained immersed. Most compositional, mechanical and structural properties improved as a result of vacuum impregnation.
TL;DR: The functional properties of heat-induced egg white gels were investigated at five pH values using the Instron Universal Machine as mentioned in this paper, showing that the texture of the gels varied with the pH.
Abstract: 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.
TL;DR: In this article, a procedure for determination of net syneresis in starch and flour materials was developed based on free water in freshly cooked pastes, synesis water expelled during cold storage and absorbed water in the contracted gel.
Abstract: A procedure for determination of net syneresis in starch and flour materials was developed based on free water in freshly cooked pastes, syneresis water expelled during cold storage and absorbed water in the contracted gel. Free water values decreased from 50% to <5%, as starch concentrations increased from 4 to 10%, indicating the need for correction of expelled+absorbed water values from free water for calculating net syneresis. Normal cereal, root and dicotyledonous seed starches exhibited a broad range of expelled water values during refrigeration, but gave high absorbed water values during freeze-thaw cycles. Waxy starches had low net syneresis during refrigeration and, except waxy corn, during freeze-thaw. For comprehensive evaluation, two refrigeration and two freeze-thaw cycles are recommended.
Journal Article•
TL;DR: In this article, the changes in weight, volume and composition of apple tissue throughout equilibration in osmotic treatments were analyzed as a function of temperature and Osmotic solution concentration.
Abstract: The changes in weight, volume and composition of apple tissue throughout equilibration in osmotic treatments were analyzed as a function of temperature and osmotic solution concentration, The effect of vacuum impregnation of the sample with osmotic solution before osmotic treatment was also studied. Two periods were differentiated. First, compositional equilibrium was achieved in a relatively short time, depending on conditions. Then a bulk flux of osmotic solution into the frult tissue occurred due to relaxation of the previously shrunken cellular structure, because of pressure gradients. True chemical and mechanical equilibrium was marked by no further changes in sample composition or weight.
TL;DR: Pale, soft, exudative (PSE), normal, and dark, firm, dry (DFD) pork was held 7 days at 4°C under light or dark then color was evaluated instrumentally and visually as mentioned in this paper.
Abstract: Pale, soft, exudative (PSE), normal, and dark, firm, dry (DFD) pork was held 7 days at 4°C under light or dark then color was evaluated instrumentally and visually. Change in reflectance (R630-R580) was used to estimate color changes due to oxymyoglobin. PSE pork was lighter (higher L * ) than normal and DFD pork, but did not change over time. An increase in a * and R630-R580 occurred the first day for normal and DFD, but not for PSE samples. A subsequent increase in hue angle and decrease in R630-R580 (loss of redness) occurred in PSE and normal, but not in DFD samples. Changes in hue angle and R630-R580 were more rapid in PSE than in normal samples. Light exposure accelerated all changes except L * . Visual redness inversely correlated with L * value.
TL;DR: In this paper, the effective partition constants of the solute between the liquid and solid phases were determined experimentally, and the constant was strongly dependent on the stirring rate at the ice front and the advance rate of the ICE front.
Abstract: Progressive freeze-concentration was effectively applied to concentrate glucose in a model solution. Effective partition constants of the solute between the liquid and solid phases were determined experimentally. The constant was strongly dependent on the stirring rate at the ice front and the advance rate of the ice front. Increasing stirring rate and reduced rate of advance lowered the effective partition constant: an improvement in freeze concentration performance. A concentration polarization model was useful to describe the effects of the operating conditions on the effective partition constant.
TL;DR: In this paper, corn, rice and potato flour were extruded with sweet whey solids (SWS) or whey protein concentrate (WPC) using low and high shear extrusion processing conditions.
Abstract: Corn, rice and potato flour were extruded with sweet whey solids (SWS) or whey protein concentrate (WPC) using low and high shear extrusion processing conditions. WPC added at product content of 25% had minimal effect on the texture of extruded products. Expansion and breaking strength were improved in some processes through changes in extrusion shear and moisture. Whey product incorporation resulted in reduced specific mechanical energy input to the process. Increasing whey product concentration beyond 25% reduced expansion and water absorption indices significantly, affecting textural hardness. Product quality characteristics were directly related to the whey product content.
TL;DR: Freeze-dried water extract of potato peels (pp), containing chlorogenic, caffeic, gallic, and protocatechuic acids, was tested for effectiveness as a natural antioxidant as discussed by the authors.
Abstract: Freeze-dried water extract of potato peels (pp), containing chlorogenic, caffeic, gallic, and protocatechuic acids, was tested for effectiveness as a natural antioxidant. The pp was prepared from peel waste of Russet Burbank potatoes. Safety concerns regarding the use of pp in foods were investigated. The pp was examined for mutagenic activity using the in vitro Salmonella typhimurium- Escherichia coli microsome assay and found to be nonmutagenic. Plate count of pp revealed <10 CFU/g. The antibacterial activity of the pp was species dependent. It was effective only at high concentration against gram negative and one gram positive bacteria but it was bacteriostatic.
TL;DR: In this paper, spectrocolorimetry, pH, TBARS, total pigment and myoglobin were measured in normal and abnormally dark-colored broiler chicken breast muscle.
Abstract: Spectrocolorimetry, pH, TBARS, total pigment and myoglobin were measured in normal and abnormally dark-colored broiler chicken breast muscle. Analyses of L * , a * and b * values revealed that a * values were highly sensitive and specific to differentiate normal from dark-colored carcasses and thus could be used as a potential diagnostic method for carcass classification at slaughter. Color characteristics (L * , a * , and b * values), pH, total pigment, myoglobin, and iron concentrations were all significantly different in dark-colored muscle when compared with normal muscle. TBARS values and percentage moisture for the two groups were not different.
TL;DR: In this article, the effects of corn particle size and distribution on the ex-trusion-cooking process was studied by analyzing process responses on-line, by expansion indices, mechanical (puncture test) and structural (computerized image analysis) prop erties of the extrudate.
Abstract: The effects of corn particle size and distribution on the ex trusion-cooking process was studied. Extrusion cooking was carried out in a twin-screw corotating extruder. The effects of particle characteristics were studied by analyzing process responses on-line, by expansion indices, mechanical (puncture test) and structural (computerized image analysis) prop erties of the extrudate. An increase in particle size for a given biochemical composition gave extrudates that were harder, with a modified expansion and lower cell density. The par ticle size distribution in the range studied was not significant. Correlations were found between expansion indices and process responses.
TL;DR: Duck egg yolk pickled by salt attained more desirable characteristics, such as orange color, oil exudate, and grittiness, than salted chicken egg yolo.
Abstract: Duck egg yolk pickled by salt attained more desirable characteristics, such as orange color, oil exudate, and grittiness, than salted chicken egg yolk. Salted duck egg yolk reached a hardening ratio of 90% in 28-days; 35 days were required for the salted chicken egg yolk to achieve the same hardening. Moisture content of egg yolk affected the quantity of extracted lipid, an index of oil exudation. The moisture content of duck egg yolk was 19%, and the extracted lipid was 30%. But less than 4% lipid was extracted when moisture content was >27.5%. Under scanning electron microscopy, yolk spheres dominated the yolk structure probably responsible for the gritty texture.
TL;DR: In this paper, the individual and combined effects of muscle vitamin E level, cooking conditions (duration, temperature and rate) and packaging on lipid oxidation in refrigerated cooked pork were examined.
Abstract: The individual and combined effects of muscle vitamin E level, cooking conditions (duration, temperature and rate) and packaging on lipid oxidation in refrigerated cooked pork were examined. Oxidative stability following cooking was higher in pork with a higher vitamin E level (p<0.01), cooked at a lower cooking temperature (p<0.01), cooked for a shorter time (p<0.01), cooked at a faster cooking rate (p<0.05) or stored in vacuum packs (p<0.01). Significant two-way and three-way interactions were observed between the effects of muscle vitamin E level, cooking conditions and packaging on lipid oxidation. Adopting more than one of these approaches to minimize lipid oxidation was more effective than adopting a single approach.
TL;DR: In this paper, the effect of an oil-soluble emulsifier upon adsorption properties of β-casein and β-lactoglobulin at the oil-water interface was studied.
Abstract: The effect of an oil-soluble emulsifier upon adsorption properties of β-casein and β-lactoglobulin at the oil-water interface was studied. Addition of emulsifier improved the emulsification properties, but lowered emulsion stability. Higher concentrations decreased emulsification capacity, due to an increase in oil phase viscosity, and interfered with several protein assays, except the o-phthaldialdehyde (OPA) assay. Depletion measurements revealed that the emulsifier displaced β-casein more readily than β-lactoglobulin from the surface of droplets, which correlated with emulsification and stability measurements. Displacement of proteins was not complete due to emulsifier-induced formation of a multiple w-o-w emulsion, which accounted for the missing protein in the continuous phase.
TL;DR: In this paper, the effects of wheat protein on the texture properties of mechanically separated poultry (MSP) smoked sausages were investigated by a partial 3* 3 * 3 factorial design with two blocking factors (3 time periods and 9 panelists).
Abstract: The effects of wheat protein on the texture properties of mechanically separated poultry (MSP) smoked sausages were investigated by a partial 3 * 3 * 3 factorial design (water, wheat protein and method of protein preparation) with two blocking factors (3 time periods and 9 panelists). The methods of wheat protein preparation did not influence any measurement. Sensory data indicated that added water affected hardness, springiness, and juiciness (p<0.05) of samples, and added wheat protein affected hardness, cohesiveness of mass, juiciness, and wheat flavor (p< 0.05). Instrumental data showed that Hardness, Springiness and Cohesiveness decreased with increasing water content. (p<0.05), and increasing wheat protein levels increased Hardness and Cohesiveness (p<0.05).