Showing papers in "Journal of Food Science in 1997"

Comparison of Spray‐drying, Drum‐drying and Freeze‐drying for β‐Carotene Encapsulation and Preservation

Abstract: Pure β-carotene was encapsulated in 25 Dextrose Equivalent maltodextrin by three drying processes (spray, freeze and drum) Stability was studied at 11% and 32% RH and 25°C, 35°C and 45°C No significant influence of %RH was observed on the retention of β-carotene Oxidation followed first order kinetics with an initial fast first order reaction followed by a second much slower first order reaction period Although drum-drying caused more initial loss in drying, the lower surface carotenoids and larger particle size resulted in greater stability as compared to the other methods The chromametric measurements of “L” and “a” corresponded to the other kinetics and indicated that the first period rapid loss corresponded to the oxidation of surface carotenoids

Physicochemical changes in Pacific whiting muscle proteins during iced storage

Abstract: No changes in actomyosin Ca 2+ -, Mg 2+ -, or Mg 2+ -Ca 2+ -ATPase activities were observed during iced storage of Pacific whiting fillets, but Mg 2+ -EGTA-ATPase increased with a loss of Ca 2+ -sensitivity. Surface hydrophobicity of actomyosin increased substantially within 2 days, but not total sulfhydryl (SH) content. During longer storage, the SH content decreased gradually, but surface hydrophobicity remained constant. Autolytic degradation products increased in fish muscle with storage time. Myosin heavy chain (MHC) was degraded by 45% within 8 days, but no noticeable difference was observed in actin. Results indicated that autolysis may be the main cause of physicochemical changes in Pacific whiting muscle proteins during iced storage.

High pressure and temperature effects on enzyme inactivation in strawberry and orange products

Abstract: High hydrostatic pressure treatment (50-400 MPa) combined with heat treatment (20-60°C) effects on peroxidase (POD), polyphenoloxidase (PPO) and pectin methylesterase (PME) activities of fruit-derived products were studied. Assays were carried out on fresh orange juice and strawberry puree. Pressurization/depressurization treatments caused a significant loss of strawberry PPO (60%) up to 250 MPa and POD activity (25%) up to 230 MPa, while some activation was observed for treatments carried out in 250-400 MPa range for both enzymes. Optimal inactivation of POD was using 230 Mpa and 43°C in strawberry puree. Combinations of high pressure and temperature effectively reduced POD activity in orange juice (50%) to 35°C. The effects of high pressure and temperature on PME activity in orange juice were very similar to those for POD.

Gelatin from cod skins as affected by chemical treatments

Abstract: Concentrations of sodium hydroxide, sulfuric and citric acids used in processing gelatin from cod skins affected both yield and quality. The highest yield of gelatin was obtained when low concentrations [0.1–0.2% (w/v)] of sulfuric acid and sodium hydroxide were applied to the skins followed by treatment with 0.7% (w/v) citric acid. The effects on bloom value, viscosity, odor, clarity, color and pH of the gelatin varied. However, the use of 0.7% (w/v) citric acid in different combinations with sodium hydroxide and sulfuric acid usually gave best results. Freezedried gelatin had considerably higher bloom value than air-dried gelatin.

Whey protein emulsion film performance as affected by lipid type and amount

Abstract: Beeswax, candelilla wax, carnauba wax, and a high-melting fraction of anhydrous milkfat were homogenized with whey protein to produce edible emulsion films Lipid type and amount were important in controlling the emulsion film water vapor permeability (WVP) The WVPs of the beeswax and milkfat emulsion films were significantly lower than that of films from lower moisture transmitters, carnauba and candelilla wax Lipid WVP and degree of viscoelasticity determined the barrier properties of the films A significant reduction in WVP of whey protein films could be achieved using large volume fractions of lipid depending on lipid type

Physical Properties of Whey Protein Stabilized Emulsions as Related to pH and NaCl

Abstract: Corn oil-in-water emulsions (20 wt%, d32∼ 0.6 μm) stabilized by 2 wt% whey protein isolate were prepared with a range of pH (3–7) and salt concentrations (0–100 mM NaCl), and particle size, rheology and creaming were measured at 30°C. Appreciable droplet flocculation occurred near the isoelectric point of whey protein (pH 4–6), especially at higher NaCl concentrations. Droplet flocculation increased emulsion viscosity and decreased stability to creaming. Results are related to the influence of environmental conditions on electrostatic and other interactions between droplets.

Seasonal Changes in Lipid Composition of Sardine (Sardina pilchardus)

Abstract: Sardine (Sardina pilchardus) lipids have important nutritional characteristics because of their high level of ω3 fatty acids. Studies of the lipid composition of this pelagic species, studies were carried out monthly during one year. Total lipids ranged between 1.2% and 18.4% (w/w). The nonpolar lipids were dominant, mainly composed of triacylglycerols and highest in the fatty season. Phosphatidylcholine (PC), and phosphatidylethanolamine (PE) were the principal polar lipids. They were both high in ω3 polyenoic fatty acids mainly 20:5ω3 and 22:6ω3. PC and PE were isolated and their fatty acid profiles determined; PE was higher in 22:6ω3 than PC.

Bacteriocins applied to food packaging materials to inhibit Listeria monocytogenes on meats

Abstract: Bacteriocins in powders were produced from milk-based media and applied to food packaging films. Nisin and pediocin “powders” were retained in casings during dialysis. Antilisterial casings were prepared by internal coating with pediocin. Antilisterial activity applied in powdered form was retained during processing and retained on contact food packaging surfaces. Pediocin powder was applied to plastic packaging bags at 7.75 μg/cm2. Meats and poultry samples were inoculated with Listeria monocytogenes. The bags coated with pediocin powder completely inhibited growth of inoculated L. monocytogenes through 12 wk storage at 4°C. Applying bacteriocins to food packaging films is an effective approach to reduce L. monocytogenes contamination in meats and poultry.

Handling Stress and Storage Temperature Affect Meat Quality of Farmed-raised Atlantic Salmon (Salmo Salar)

Abstract: Salmon slaughtered by standard routines (control) or stressed by confinement for 10 min before stunning and then stored at 0.4 or 3.3°C for 9 days were compared. Handling stress led to lower muscle phosphocreatine (p<0.001), adenosine-5′-triphosphate (p<0.05) and shorter pre-rigor period. Storage temperature affected external quality index, white muscle pH and K-value (degradation products of ATP). Stress produced a softer fillet (p<0.001). A lower breaking strength (p<0.01) was found in fish stored at 0.4°C. Sensory tests distinguished the control/stress groups within the 0.4°C chilling regime and the 0.4°C/3.3°C chilling groups within the control regime. Stress caused a lower score for texture (p<0.05) both at 0.4 and 3.3°C and for odor at 3.3°C in a descriptive sensory test. No detectable effects of stress or storage temperature were found on flavor or color.

Dietary Influences on Bovine Milk cis‐9,trans‐11‐Conjugated Linoleic Acid Content

Abstract: The effects of grass dry matter (DM) allowance and dietary supplements of full fat rapeseeds on levels of cis-9,trans-11 octadecadienoic (CLA) acid in bovine milk were investigated. Grass allowance of 16 kg/(cow * day) resulted in reduced (p<0.05) milk fat CLA levels (3.91 mg CLA/g fat) compared to 20 kg/(cow * day) after 19 wk treatment. CLA levels increased in milk fat from cows on a high-rapeseed-supplemented diet (p<0.001) (1650 g/(cow * day) full fat rapeseed) compared to the control (pasture) and low rapeseed (p<0.01) (825 g/(cow * day) full fat rapeseed) supplemented diets. The variation in milk fat CLA levels among individual cows over both trials was 1.5-16 mg/g.

Solubility and emulsifying properties of soy protein isolates modified by pancreatin

Abstract: Soy protein isolates (SPI) with varying degrees of hydrolysis (DH of 7, 11, 15, 17%) were produced using pancreatin. The surface hydrophobicity indices of pancreatin hydrolyzed SPI (PSPI) (34.5, 34.9, 39. 1, and 40.7 for 7, 11, 15, 17% DH, respectively) were higher than that of SPI (10.5) and control SPI (CSPI) (12.5, 11.9, 12.9, and 12.6 for 10, 60, 120, and 180 min incubation, respectively). The solubilities of PSPI at pH 4.5 were 2.7, 9.1, 11.9, and 18.7%, for 7, 11, 15, and 17% DH, respectively, while the solubilities of SPI and CSPI at the same pH were about 1. 6%. Solubilities of PSPI at pH 7. 0 were > 90% for all DHs tested, while those of SPI and CSPI were 85%. The emulsifying activity index (EAI) of PSPI increased with increasing DH. PSPI with 15% DH had highest EAI (1. 122) which was higher (P < 0. 05) than those of SPI (0.550) and CSPI after 120 min incubation without enzyme (0.568). These results suggest that PSPI could be used as an ingredient for emulsified products and where high solubility at low pH is required.

Production of Restructured Meat using Microbial Transglutaminase without Salt or Cooking

Abstract: To produce restructured meat, microbial transglutaminase (MTGase) was evaluated for its ability to introduce covalent crosslinks between protein molecules. Pork muscle cubes were mixed with MTGase and held at 5°C for 2 hr for the enzyme reaction. Restructured products were analyzed for binding strength without cooking. MTGase treatment resulted in effective binding of meat pieces provided there was addition of salt (NaCI). To ensure proper binding without NaCI, some food proteins with MTGase were also investigated. Meat cubes in combination with MTGase and sodium caseinate showed acceptable bind, and sodium caseinate appeared to be a superior substrate for the crosslinking to meat proteins than soy protein, whey protein, or gelatin. These results suggest a useful method for producing restructured meat which can be distributed in the raw, chilled state.

Physical and Sensory Properties of Model Foods Supplemented with Cauliflower Fiber

Abstract: Cauliflower floret/curd and stem, as by-products of processing, are a source of pectic-polysaccharide-rich fiber concentrates for use as water and oil binding agents and textural agents to improve the properties of model foods. Dehydration resulted in a 10% decrease in methyl esterification at above 40°C. Water retention capacity of florets (40°C) was reduced from 12.8 g/g to 5.7 g/g in 75°C dried samples, demonstrating the importance of matrix structure rather than polysaccharide composition for functional properties. Incorporation gave a 10% increase in the yield of beefburgers and a partial substitution for purified gums in sauces. Cauliflower fibers can be incorporated into food systems at concentrations found in vegetables but sensory characteristics depend on processing history.

Composition, Solubility and Emulsifying Properties of Granules and Plasma of Egg Yolk

Abstract: Yolk was fractionated by a low speed centrifugation into granules and plasma. The composition, solubility and emulsifying properties of granules and plasma were compared to those of industrial spray-dried yolk. Granules contained about half the lipids and cholesterol and about double the proteins of yolk and plasma. Yolk and granules required an ionic strength ≥ 0.3M sodium chloride to become solubilized at pH 7.0, whereas plasma was solubilized at any ionic strength. At about 80% solubility, yolk, granules and plasma had similar emulsifying activities and granules had the best emulsion stabilization. Results suggest that granules could be used as stabilizers in food emulsions.

Physicochemical properties of whey protein-stabilized emulsions as affected by heating and ionic strength.

Abstract: Corn oil-in-water emulsions (19.6 wt%; d 32 0.6 μm) stabilized by 2 wt% whey protein isolate (WPI) were prepared with a range of pH (3-7) and salt concentrations (0-100 mM NaCl). These emulsions were heated between 30 and 90°C and their particle size distribution, rheological properties and susceptibility to creaming measured. Emulsions had a paste-like texture around the isoelectric point of WPI (pH 5) at all temperatures, but tended to remain fluid-like at pH >6 or <4. Heating caused flocculation in pH 7 emulsions between 70 and 80°C (especially at high salt concentrations), but had little effect on pH 3 emulsions. Flocculation increased emulsion viscosity and creaming. Results were interpreted in terms of colloidal interactions between droplets.

Hydration Kinetics of Red Kidney Beans (Phaseolus vulgaris L.)

Abstract: Soaking of dry red kidney beans was studied at 20, 30 40 and 60°C by the method of weight gain until equilibrium conditions were attained. Water absorbed during soaking was a function of both soaking time and temperature. Soaking at high temperatures increased the hydration rate constant and decreased soaking time to achieve equilibrium. Compared to unblanched beans, the application of a pre-blanching step considerably reduced hydration times of blanched beans. Due to the plasticity effect acquired upon blanching, blanched beans showed a significantly high hydration rate constant and exhibited a more constant equilibrium moisture content regardless of soaking temperature. Activation energy values (Ea) of the hydration process were 6.48 Kcal/mole for blanched and 14.25 for unblanched beans.

Fractional Conversion for Determining Texture Degradation Kinetics of Vegetables

Abstract: Fractional conversion (f) takes into account the nonzero texture property upon prolonged heating. This was applied as an alternate technique for reanalyzing texture degradation kinetics based on published data which indicated that the softening of vegetables followed a dual mechanism first order kinetic model. The plot of the logarithm of 1-f vs heating time was linear through log cycles indicating the reaction was first order with a single rate constant and the substrate b was better characterized by the equilibrium (or maximum retainable) texture property. A possible explanation was developed for negative activation energies which had been reported for the second mechanism with some vegetables.

Modified Soy Proteins with Improved Foaming and Water Hydration Properties

Abstract: Soy proteins were modified by alkali treatment at pH 10.0, followed by papain hydrolysis. Solubility, water hydration capacity (WHC), surface hydrophobicity, foaming and emulsifying properties of unmodified, alkali-treated, and papain-modified soy protein (PMSP) were compared. PMSP exhibited higher solubility (100% at pH > 7.0), WHC (3.13) and hydrophobicity (40.8) than unmodified soy protein which had solubility 68.5%, WHC 0.21, and hydrophobicity 8.1. The PMSP had foaming capacity (22.0 mL) similar to egg white (21.2 mL) at pH 7.0; and enhanced foam stability (36.4) compared to the unmodified control (32.9). In general, alkali-treated soy had lower functional properties. Emulsifying properties of PMSP and alkali treated soy were unchanged by the modification. PMSP could be used as an egg white substitute in foaming applications at neutral pH.

Sugar and Fat Effects on Sensory Properties of Ice Cream

Abstract: Vanilla ice cream with 8, 13 or 18% sucrose and 10, 14 or 18% butterfat was evaluated by descriptive analysis (DA) with 15 judges, instrumental texture measurements (ITM), and hedonic rating with 146 consumers. Increased sugar caused higher vanilla, almond, buttery, custard/eggy, sweetness, fatty, creamy, doughy and mouthcoating characteristics, and lower coolness, ice crystals, melt rate (ITM) and hardness (ITM). Increased fat caused higher buttery, custard/eggy and sweet flavor, fatty, creamy, doughy and mouthcoating texture, and lower color, ice crystals and melting rate (DA). Acceptability was positively related to the vanilla, creamy, fatty and milky characters, and negatively related to color, ice crystals and ITM hardness.

Hydrolytic Stability and Changes in E Vitamers and Oryzanol of Extruded Rice Bran During Storage

Abstract: Rice bran was extruded at 110, 120, 130, and 140°C with post extrusion holding times of 0, 3, and 6 min and stored at ambient temperatures for 1 yr. Holding time had no effect (p>0.05) on hydrolytic stability whereas 110°C was slightly less effective in maintaining hydrolytic stability. Increased holding times reduced (p<0.05) total vitamin E content. Oryzanol concentration was lower (p<0.05) only after 6 min holding time. Oryzanol was relatively more stable to extrusion temperatures than vitamin E. Thc highest retentions of total vitamin E and oryzanol were found in raw rice bran during storage. Increased extrusion temperatures reduced the retention of vitamin E and oryzanol during storage.

Color of Minimally Processed Potatoes as Affected by Modified Atmosphere Packaging and Antibrowning Agents

Abstract: Minimal processing of potatoes was studied by using different treatments of cut potatoes in combination with modified atmosphere packaging. Different packaging materials and peeling methods were evaluated. An L-cysteine (0.5%) and citric acid (2%) mixture prevented browning of potatoes effectively. Active modification of the atmosphere inside the package was necessary to achieve extended shelf-life. Nitrogen flushing was more effective than other gas treatments with a highly permeable multilayered polyolefin packaging material. Hand peeling and lye peeling resulted in better quality, but abrasion peeling was undesirable for fresh potatoes. The shelf-life of the minimally processed products could be extended to nearly 3 wk under refrigerated storage.

Spray Drying, Freeze Drying, or Freezing of Three Different Lactic Acid Bacteria Species

Abstract: Lactococcus lactis ssp. cremoris D11, Lactobacillus casei ssp. pseudoplantarum UL137, and Streptococcus thermophilus CH3TH, were separately frozen, freeze dried or spray dried, and tested for survival and lactic acid production before and after processing. Virtually all cells survived freezing. Of the survivors, 60 to 70% survived the dehydration step of freeze drying. In contrast to freezing and freeze drying, spray drying caused considerable delay in lactic acid production and reduction in survival. After spray drying, survival was greatest for S. thermophilus and lowest for Lc. cremoris.

Extraction and Functional Properties of Barley β-Glucan as Affected by Temperature and pH

Abstract: Barley is high in β-glucan, a soluble fiber component. Effects of extraction temperature (40 55 C) and pH (7.0 10.0) on recovery, purity and functional properties of β-glucan were investigated on whole Condor barley flour. At pH 7.0, 8.0 and 55°C, 86.5% of the β-glucan in the feed flour was recovered in the gum product with 89.1% (d.w.b.) purity. β-Glucan content increased (p < 0.05) with temperature but not with pH. Apparent viscosity of 1% (w/v) dispersions of β-glucan gum from pH 7.0 increased (p < 0.05) with extraction temperature at constant shear rate and viscosity decreased slightly with increasing shear rate. Whippability and foam stability of gums from pH 8.0 and 45°C were maximum. Emulsions prepared with β-glucan gum from pH 7.0 and 55@c were 63% stable after centrifugation. Barley β-glucan shows great potential as a thickener or stabilizer.

Protein and salt effects on Ca2+-induced cold gelation of whey protein isolate

Abstract: Increasing whey protein concentration (from 6 to 10% w/v) decreased gel opacity but increased gel strength and water-holding capacity (WHC). Increasing CaCl 2 concentration (from 5 to 150 mM) increased gel opacity and gel strength at the high protein concentration (i.e., 10%). However, it lowered gel strength at protein concentration <10%. Young's modulus and distance to fracture values indicated that gels were most rigid at 30 mM CaCl 2 , at which point the extent of aggregation (measured by turbidity) was the highest. Increasing CaCl 2 concentration from 5 to 150 mM slightly affected the WHC of Ca 2+ -induced gels. Protein concentration was the major factor in determining fracture properties and WHC.

Catalytic Mechanism of Lipid Oxidation following High Pressure Treatment in Pork Fat and Meat

Abstract: Addition of citric acid (0.02%) inhibited the increased rate of lipid oxidation found in rendered pork fat following pressure treatment (650-800 MPa). This indicated that transition metal ions were probably released from complexes and became available to catalyze lipid oxidation in the pressure treated fat. In minced pork and washed fibers citric acid was less effective in inhibiting oxidation in pressure treated samples because of its pH lowering effects. However, the less acidic ethylenediaminetetraacetic-acid disodium salt (Na 2 EDTA) was an effective antioxidant in these pressure treated (400 MPa and 800 MPa) systems. This further indicated that metal catalysts (probably iron) were released from complexes during pressure treatment to catalyze lipid oxidation.

Analysis of visual quality attributes of white shrimp by machine vision

Abstract: An important component of shrimp quality evaluation is determination of visual attributes by trained inspectors. This is subjective, time consuming, and difficult to quantify. An automated device was developed for repeatable, objective measurement of visual quality of shrimp. The device measured the count, uniformity ratio, color, melanosis, and detected foreign objects. Shrimp area viewed by a camera was used to estimate weight after calibration, and count and uniformity ratio was calculated. The system quantified color changes in white shrimp during iced storage. Melanosis was quantified and correlated with the grading of a trained inspector. The method objectively measured visual quality attributes of white shrimp in less than 1 min per sample.

Heat inactivation kinetics of apple polyphenoloxidase and activation of its latent form

Abstract: Heat inactivation kinetics of crude polyphenoloxidase (PPO) from six apple cultivars (Golden Delicious, Starking Delicious, Granny Smith; Gloster, Starcrimson and Amasya) were studied at three temperatures (68°, 73° and 78°C). PPO activity initially increased and then decreased with heat, following a first order kinetic model. Increase in activity indicated presence of latent PPO. Regression coefficients for the linear portions of inactivation curves were computed to determine inactivation parameters. Reaction data at 78°C revealed that PPO in Amasya was the least and Starking Delicious the most heat-stable. Rate constants for heat inactivation at 78°C ranged from 15.99-28.27 . 10 -2 min -1 . Activation energies varied between 54.7-77.2 kcal . mol -1 with z values of 7.1-10.0C°. PPO in apples was generally more heat-stable than PPO in most fruits.

Phenoloxidases in Portabella Mushrooms

Abstract: Tyrosinase, laccase, and peroxidase activities were detected in crude extracts from commercial Portabella mushrooms Tyrosinase was present in larger amounts than either laccase or peroxidase Catechol showed the greatest activity as a substrate for tyrosinase while diaminobenzidine was found to be a good substrate for estimating laccase and peroxidase activity Two tyrosinase and three laccase isoforms were detected after native electrophoresis At least 10 tyrosinase isoforms were observed after isoelectric focusing The distribution of these forms varied in different tissues Browning reactions in Portabella mushrooms are a result of tyrosinase rather than laccase or peroxidase

Thermal Stability of Invertase in Reduced-Moisture Amorphous Matrices in Relation to Glassy State and Trehalose Crystallization

Abstract: The thermal stability of enzyme invertase in reduced-moisture modelsystems of maltodextrin (MD), polyvynilpyrrolidone (PVP; MW 40,000)and trehalose heated at 907C was studied. Significant invertase inacti-vation was observed in heated glassy PVP and MD systems kept wellbelow their glass transition temperature (T g ), but the enzyme was fairlystable in rubbery trehalose systems. However, at moisture contents whichallowed trehalose crystallization rapid thermal inactivation of invertasewas observed. Invertase inactivation in heated PVP, MD and trehalosesystems of reduced-moisture could not be predicted on the basis of glasstransition and this was particularly true for trehalose. Conditions whichwould allow collapse of the systems and crystallization of trehalose werefairly well predicted based on the estimated T g of model systems.Key Words: invertase, thermal inactivation, glass transition, trehalose,crystallization INTRODUCTION D RYINGOFFOODSYSTEMS is an effective preservation methodbut its physico-chemical basis is not completely understood. In-formation on the mobility in the highly viscous matrices of de-hydrated materials is fundamental to understanding the kineticprocesses involved (Noel et al., 1994; Whitaker, 1995). The sta-bilization of enzymes and other biomaterials (e.g. microorgan-isms) by their incorporation into aqueous carbohydrate orpolymer solutions, followed by drying to low moisture to im-mobilize such labile materials in a solid matrix is a known pres-ervation procedure (Mugnier and Jung, 1985; Colaco et al.,1992; Palumbo et al., 1995). Several studies have demonstrateda relationship between temperature, moisture content and dura-tion of thermal treatment on the stability of enzymes at reducedmoisture (Multon and Guilbot, 1975; Whitaker, 1995).Colaco et al. (1992) showed that extremely fragile biomole-cules such as DNA restriction and modifying enzymes could bedried

Kinetics of formation of polar heterocyclic amines in a meat model system.

Abstract: A model system was used to examine kinetics of formation of polar heterocyclic amines by heating the precursors creatinine, glucose and amino acids in proportions similar to those in bovine meat but at higher concentrations. Formation of heterocyclic amines was studied between 150 and 225°C for 0.5-120 min, depending on temperature. Heated samples were subjected to solid phase extraction and HPLC analysis, with photodiode array detection for identification and quantification of heterocyclic amines. IQx, MeIQx, 7,8-DiMeIQx, 4,8-DiMeIQx, PhIP, harman and norharman were identified. A first-order reaction model and the Eyring equation were fitted to the formation of polar heterocyclic amines to obtain rate constants and their temperature dependence.