Showing papers in "Journal of Food Science in 2000"

Lipid Oxidation in Oil-in-Water Emulsions: Impact of Molecular Environment on Chemical Reactions in Heterogeneous Food Systems

Abstract: The susceptibility of lipids to oxidation is a major cause of quality deterioration in food emulsions. The reaction mechanism and factors that influence oxidation are appreciably different for emulsified lipids than for bulk lipids. This article reviews the current understanding of the lipid oxidation mechanism in oil-in-water emulsions. It also discusses the major factors that influence the rate of lipid oxidation in emulsions, such as antioxidants, chelating agents, ingredient purity, ingredient partitioning, interfacial characteristics, droplet characteristics, and ingredient interactions. This knowledge is then used to define effective strategies for controlling lipid oxidation in food emulsions.

Production and Properties of Spray‐dried Amaranthus Betacyanin Pigments

Abstract: Amaranthus betacyanin extracts were spray-dried using a range of maltodextrins [10-25 dextrose equivalent (DE)] and starches (native/modified) as carrier and coating agents at 5 inlet/outlet air temperatures and 4 feed solid contents. Higher inlet/outlet air temperatures caused greater betacyanin loss during spray drying, and affected slightly the pigment stability during storage. Adding maltodextrins and starches significantly reduced the hygroscopicity of the betacyanin extracts and enhanced storage stability. The 25 DE/10 DE mixed powders provided a longer predicted half-life (63.6 wk) compared to the 25 DE and the 10 DE powders separately. The best dried pigment-containing powder made was superior to commercial red beet powder in physical properties.

Classification and Antihypertensive Activity of Angiotensin I-Converting Enzyme Inhibitory Peptides Derived from Food Proteins

Abstract: Angiotensin I-converting enzyme (ACE)-inhibitory peptides from the thermolysin digest of chicken muscle and the peptic digest of ovalbumin were isolated. However, some of them failed to show antihypertensive activity in spontaneously hypertensive rats (SHR). To clarify this discrepancy, ACE-inhibitory peptides from various sources were preincubated with ACE before measurement of ACE-inhibitory activity and classified into 3 groups: (1) inhibitor type, IC50 values of peptides that are not affected after preincubation with ACE; (2) substrate type, peptides that are hydrolyzed by ACE to give peptides with weaker activity; and (3) prodrug-type inhibitor, these peptides are converted to true inhibitors by ACE or gastrointestinal proteases. Peptides belonging to the 1st and the 3rd groups exert antihypertensive activities even after oral administration in SHR.

Changes in anthocyanins and polyphenolics during juice processing of Highbush blueberries (Vaccinium corymbosum L.)

Abstract: Frozen blueberries (Vaccinium corymbosum L.) were processed into juice and concentrate, and the changes in anthocyanin pigments and polyphenolics (cinnamates, procyanidins, flavonol glycosides) were monitored. While juice yield was 83%, only 32% of the anthocyanins were recovered in single-strength juice. Flavonol, procyanidin and chlorogenic acid recoveries in juice were 35%, 43%, and 53%, respectively. The proportion of polyphenolics remaining in the press-cake residue ranged from 1% (chlorogenic acid) to 18% (anthocyanins). Pronounced losses of anthocyanins and polyphenolics during milling and depectinization are believed to be due to native polyphenol oxidase. Losses during concentration ranged from 1.5% (anthocyanins) to 20% (procyanidins). Striking changes occurred in the anthocyanin profile with malvidin glycosides being most stable and delphinidin glycosides the least.

Lipid Addition to Improve Barrier Properties of Edible Starch‐based Films and Coatings

Abstract: Effects of formulation (lipid presence, type of starch, and plasticizer) on microstructure, water vapor (WVP) and gas (GP) permeabilities of films and coatings were analyzed. Plasticizer was necessary to maintain film and coating integrity and to avoid pores and cracks. Films made from high amylose starch showed lower WVP and GP than regular corn starch films; permeabilities of films with sorbitol (20 g/L) were lower than those with glycerol. The addition of 2g/L sunflower oil to the formulations decreased WVP of starch-based films; X-ray diffraction and Differential Scanning Calorimetry experiments demonstrated that films with plasticizer and lipid showed lower crystalline-amorphous ratio compared to films without additives. Microstructural observations helped explain the decrease of the film permeabilities during storage.

High Pressure Processing

Abstract: Scope of Deliverables: This section covers high pressure processing as an alternative technology for preservation of foods. It includes critical process factors, their effect on Inactivation levels and mechanisms of inactivation, as well as pathogens of concern and recommendations for surrogates, Methods to handle deviations are also described.

Physicochemical and Sensory Characteristics of Fish Gelatin

Abstract: The physicochemical differences between pork and fish gelatin and the effect of melting point on the sensory characteristics of a gelatin-water gel were investigated. Gelatin gel strength (measured as Bloom) and melting point of gelatin gels were measured, and quantitative descriptive analysis sensory tests were performed. The dependence of the gelatin gel strength and the melting point of fish gels on gel concentration, maturation time, maturation temperature, pH, and the influence of NaCl and sucrose were similar to those for pork gelatin. The flavored fish gelatin dessert gel product had less undesirable off-flavor and off-odor and a more desirable release of flavor and aroma than the same product made with an equal Bloom, but higher melting point, pork gelatin.

Diffusion of acetic and propionic acids from chitosan-based antimicrobial packaging films.

Abstract: The diffusion of acetic or propionic acids from thin (44 to 54 m m) chitosan-based antimicrobial packagingfilms in which they were incorporated was measured after immersion of the films in water, and the effects of pH (5.7,6.4, or 7.0) and temperature (4 °C, 10 °C, or 24 °C) on diffusion were investigated. The kinetics of acetic- and propi-onic-acid release deviated from the Fickian model of diffusion. Diffusion was found to be unaffected by pH in therange of values tested, but a decrease in temperature from 24 °C to 4 °C resulted in a reduction of diffusion coefficientsfrom 2.59 × 10 -12 m 2 .s -1 to 1.19 × 10 -12 m .s for acetic acid and from 1.87 × 10 m 2 .s -1 to 0.91 × 10 -12 m 2 .s -1 for propionicacid. The effect of temperature on diffusion was well (r 2 . 0.9785) described by an Arrhenius-type model with activa-tion energies of 27.19 J.mole -1 (acetic) and 24.27 J.mole (propionic). Incorporation of lauric acid or essential oils(cinnamaldehyde or eugenol) into the chitosan film at the time of preparation produced a subsequent reduction in thediffusion of acetic or propionic acid, and maximum effects were obtained with lauric acid and cinnamaldehydeincorporated to final concentrations of 1.0% and 0.5% (w/w), respectively.Key Words: diffusion, acetic, propionic, chitosan, packaging

Tomato Flavor and Aroma Quality as Affected by Storage Temperature

Abstract: Studies were conducted to describe flavor and aroma in ripe tomatoes stored at 5, 10, 12.5 and 20 °C. Fruit stored for 2 d below 20 °C were rated by trained sensory panelists as significantly lower (P < 0.05) in ripe aroma, tomato flavor, compared to those stored at 20 °C. Fruit stored at 5 °C for 4 d were rated significantly lower in ripe aroma, sweetness, tomato flavor, and significantly higher in sourness, compared to those stored at 20 °C. Following 8 and 12 d storage, fruit at 5 °C were rated lowest in ripe aroma and sweetness. Significant reductions in important GC aroma volatiles and chemical composition and electronic nose analyses concurred with sensory

Apple Wraps: A Novel Method to Improve the Quality and Extend the Shelf Life of Fresh‐cut Apples

Abstract: A novel method was developed to extend the shelf life and improve the quality of fresh-cut produce. Edible coatings and films were made from apple puree with various concentrations of fatty acids, fatty alcohols, beeswax, and vegetable oil. Apple pieces were coated with solutions or wrapped in preformed films. Changes in moisture content and color were measured during storage. Increasing concentrations of lipids significantly improved the moisture barrier properties of films. Water vapor permeability varied from 69 to 325 g mm/kPa d m2. Apple-based wraps significantly reduced moisture loss and browning in fresh-cut apples. Color was preserved for 12 d at 5 °C. Wraps were significantly more effective than coatings.

Plasticizing—Antiplasticizing Effects of Water on Physical Properties of Tapioca Starch Films in the Glassy State

Abstract: The effects of moisture sorption on physical properties of native and cross-linked starch films in the glassy state were studied. Water played a dual role as a plasticizer or an antiplasticizer, depending on the physical property measured. Plasticizing effects were clearly evident in the case of the calorimetric glass transition tempera- ture (T g ), tensile modulus, linear expansion, and water vapor permeability. In contrast, antiplasticization by water resulted in maxima in tensile strength, strain-at-break, and toughness of films that were observed at an intermedi- ate moisture content ranging from 4% to 8% (RVP 0.1 to 0.4). The seemingly contradictory effects of water on me- chanical properties associated with lower and higher deformation of starch films were reconciled by assigning dif- ferent roles to water operating primarily via opposite entropic/free volume effects. Relationships, if any, between

Plasma protein and soy fiber content effect on bologna sausage properties as influenced by fat level

Abstract: The effects of plasma protein (PP) and soy fiber (SF) content on the properties (binding properties, color, and texture) of bologna sausages as influenced by fat level (F) were assessed by response surface methodology (RSM). Higher soy fiber and plasma protein contents favored the formation of harder, chewier structures with improved fat and water binding properties. Fat reduction decreased textural properties and increased weight loss. Cooking loss was affected (P < 0.05) by interactions between PP and F and chewiness was affected (P < 0.05) by interactions between SF and F. Plasma protein influenced binding and textural properties more than soy fiber and was, therefore, thought best to limit the effect of fat reduction.

Postmortem Biochemical and Functional Characteristic of Monterey Sardine Muscle Stored at 0 °C

Abstract: Postmortem changes of sardine muscle during 15 d storage at 0 °C were studied to evaluate its quality and functionality. No microbial deterioration was detected since trimethylamine and histamine concentration remained low with final values of ≤ 1.62 mg/100g and 0.00018 ppm, respectively. A final proteolytic activity ≤ 20 μg Tyrosine/min/g protein was detected. Lipid oxidation from moderate to advanced was detected after day 5 with values of 31.8 to 33.9 meq/kg and 26 mg/kg for peroxide value and thiobarbituric acid value respectively. Muscle protein showed no gel-forming ability. Extraction of myofibrillar protein decreased 45% and 81% at day 5 and 15 respectively. Overall results indicated that good quality was maintained during the storage period with a final K value of 50.7% when proper handling practices were implemented.

Anthocyanins, Phenolics, and Antioxidant Capacity of Processed Lowbush Blueberry Products

Abstract: Temperature, pH, and oxygenation of extracted blueberries were examined to determine how processing may affect the antioxidant capacity of blueberry food products. Extraction of fruit at 60 °C resulted in higher recovery of anthocyanins and antioxidant capacity, compared to extracts obtained at 25 °C. Subsequent room temperature storage resulted in losses in anthocyanins and antioxidant capacity only in those extracts obtained at 60 °C. Antioxidant capacity was greatest in pH 1 extracts, compared to extracts at pH 4 and 7. Oxygenation was detrimental to both anthocyanins and antioxidant capacity. Antioxidant capacity of processed products was positively correlated with anthocyanin (R = 0.92) and phenolic content (R = 0.95), and negatively correlated with % polymeric color (R = -0.64). In general, products that had experienced less processing had a higher antioxidant capacity. Simple colorimetric tests for anthocyanins and phenolics proved to be useful indicators of antioxidant capacity in processed products.

Chemical, Physical, and Gel-forming Properties of Oxidized Myofibrils and Whey- and Soy-protein Isolates

Abstract: Myofibrils, oxidized with FeCl 3 /H 2 O 2 /ascorbate, exhibited an increase in carbonyls and amines, SH SS conversion, peptide scission, myosin polymerization, and a decrease in thermal stability and gel-formation ability. Amino-acid side chains of whey-protein isolates (WPI) and soy-protein isolates (SPI) were also modified during oxida- tion, but the thermal stability of WPI or SPI was not significantly altered. Oxidation increased elasticity of SPI gel but not that of WPI gel. Similarly, oxidation promoted interactions of myofibrils with SPI but not with WPI, resulting in > 30% increases in elasticity of the myofibril/SPI composite gel over its nonoxidized control. Hence, in processed meats

Texture and chemical characteristics of soy protein meat analog extruded at high moisture

Abstract: The relationships among extruder responses, texture, and protein solubility of soy protein meat analogs were studied. Soy protein isolate and wheat starch at 9:1 ratio were extruded at 60%, 65%, and 70% moisture contents and 137.8, 148.9, and 160 degrees C cooking temperatures. The results showed that moisture content was a more important factor on the overall product texture than cooking temperature. Lower moisture content resulted in higher die pressure, harder texture, and lower total protein solubility. At a fixed moisture content, a higher cooking temperature resulted in a softer and less chewy product but only slightly changed the protein solubility. According to partial least square regression, the data from Texture Profile Analysis, protein solubility, and extruder responses correlated well and could be used to predict each other.

High Oxygen and High Carbon Dioxide Modified Atmospheres for Shelf‐life Extension of Minimally Processed Carrots

Abstract: The impact of high O2 + high CO2 modified atmospheres (MA), on the preservation of minimally processed carrots was studied. A combination of 50% O2 + 30% CO2 prolonged the shelf life of sliced carrots compared to storage in air by 2 to 3 d. When the carrots received a pre-treatment with a 0.1% citric acid dip and a sodium alginate edible coating prior to packaging, shelf life was extended by 5 to 7 d. Advantages and disadvantages of the proposed MA over previously recommended MA (1% O2 + 10% CO2), related to a range of physicochemical and microbiological characteristics of carrots are discussed.

Effect of process conditions on the physical and sensory properties of extruded oat-corn puff

Abstract: The effect of processing variables, including screw speed (200,300, and 400 rpm), moisture content (18, 19.5, and 21%), and four different percentages (55,70,85, and 100%) of oat flour, on the extrudate physical properties (expansion, bulk density, and texture profiles) and sensory properties were studied. Increasing the percentage of oat flour resulted in extrudates with a lower specific length, higher bulk density, lower lightness, higher redness, lower yellowness, higher hardness, and lower springiness, gumminess, and chewiness. Higher moisture content reduced expansion, except for the 100% oat flour puffs. Screw speed had no significant effect on the bulk density, specific length, and expansion ratio. Principal Component Analysis showed that decreasing moisture content and increasing screw speed resulted in increased product temperature, which was highly correlated with attributes of a more expanded product such as lightness, crispness, shininess, and an open cell structure. With a higher screw speed and a higher product temperature, corn-related flavors were more likely to develop. High correlations between physical and sensory properties were observed.

Growth and Viability of Commercial Bifidobacterium spp in Skim Milk Containing Oligosaccharides and Inulin

Abstract: Two commercial strains of Bifidobacterium spp (Bf-1 and Bf-6) were cultured in 12% (w/w) reconstituted nonfat dry milk (NDM) containing 0, 0.5, 1.0, 3.0, or 5.0% (w/v) fructooligosaccharide (FOS), galactooligosaccharide (GOS), and inulin. Inoculated samples were incubated anaerobically at 37 degrees C for 48 h. Growth and activity of the cultures in the presence of FOS, GOS, and inulin were determined. Viability of each strain was assessed after 4 weeks of refrigerated storage at 4 degrees C. Growth promotion, enhancement of activity and retention of viability were greatest when Bifidobacterium Bf-1 and Bf-6 were grown in the presence of FOS followed in a descending order by GOS and inulin. The effects of oligosaccharides and inulin increased with increasing carbohydrate concentration and was maximal at 5% (w/v).

Bioactive Properties of Wild Blueberry Fruits

Abstract: Bioactive extracts from wild blueberries were isolated, fractionated, and analyzed. Antioxidant activity, cardioprotective capacity, and ability to inhibit the initiation stage of chemically-induced carcinogenesis were evaluated. Many fractions had antioxidant activity, especially those rich in anthocyanins and proanthocyanidins. The ease of isolation of bioactive compounds and the ability to obtain accurate bioassays depended strongly on the source material used. Extracts from spray-dried formulations containing magnesium citrate and tri-calcium phos- phate provided easier materials for bioactivity assessment and demonstrated antioxidant, cancer preventive and cardioprotective activity. Extracts with potent antioxidant activity degraded readily, underscoring the need for rapid alternative fractionation tactics and rigorously controlled storage conditions.

Extracting Conditions for Megrim (Lepidorhombus boscii) Skin Collagen Affect Functional Properties of the Resulting Gelatin

Abstract: Various procedures for extracting collagen and/or gelatin from megrim skins were compared on the basis of gelatin functional properties. It was possible to prepare a dry powder of soluble collagen with good viscoelastic and gelling properties, which can be converted into gelatin by dissolving at temperatures above 45 °C. Physical properties of gelatins are influenced more by extracting conditions than by imino acid composition. A high-quality, readily-dissolved gelatin was obtained from megrim skins using a pretreatment of the skins with NaCl and dilute NaOH, then swelling with 0.05 M acetic acid followed by an extraction step in water at 45 °C.

Cultivar, Maturity, and Heat Treatment on Lycopene Content in Tomatoes

Abstract: Using high performance liquid chromatography, tomato cultivars which contain the Crimson gene (og) were usually found to have higher lycopene content (5086 to 5786 μg/100 g fresh weight) than those cultivars lacking the gene (2622 to 4318 μg/100 g fresh weight). A comparison of the color readings taken from tomatoes at the equatorial region with those of the homogenate prepared from the same region showed that the hue of tomato homogenate was a better indicator of lycopene content than tomato surface hue. The tomatoes' lycopene content was not affected by ethylene treatment or cooking for 4, 8, and 16 min at 100 °C.

Extending Shelf Life of Fresh-cut Pears

Abstract: The effects of various treatments were evaluated for extending shelf-life of fresh-sliced pears. Sliced Anjou pears had browning-free color for 30 d by dipping with 1.0% ascorbic acid and 1.0% calcium lactate, but texture was soft with juice leakage. The combination treatment of 0.01% 4-hexylresorcinol (4-HR), 0.5% ascorbic acid and 1.0% calcium lactate can provide 15 to 30 d shelf-life for Anjou, Bartlett, and Bosc pears when the pears are sliced at an average ripeness of 43, 49, and 38 Newton respectively, with 2 min dipping, partial vacuum packaging, and 2 to 5 °C storage. 4-HR residual content ranged from 1 to 7 ppm after 14 d storage. Panelists could detect a flavor difference between 0.01% 4-HR treated pears and controls.

Viscoelastic Changes of Rice Starch Suspensions During Gelatinization

Abstract: Dynamic rheometry was utilized to characterize viscoelastic changes during heat-induced gelatinization of 2 domestic rice starch suspensions, 1 from waxy and the other from indica rice. Gelatinization included 4 stages: suspension into sol, sol transition to gel, network destruction, and network strengthening. Increase in storage modulus (G') was observed as early as about 47 degrees C. For indica rice, the maximum value (G'(max)) was higher, and the decrease afterwards was slower, owing to its higher amylose content. The effects of heating time and temperature were found additive. Sealing samples with oil affected the accuracy of measurement. Finally, the network of starch gels had a larger fractal dimension than that of soy protein isolates previously investigated, suggesting firmer food texture.

Ohmic and Inductive Heating

Abstract: Scope of Deliverables: This section covers information, where available, on kinetics and relevant safety considerations for processing commercially sterile or extended shelf-life products produced by ohmic and inductive heating. It does not include combinations of other alternate process technologies with ohmic and inductive heating, since the number of potential combinations is infinite but no information is available.

Characterization and Functional Properties of Rice Bran Proteins Modified by Commercial Exoproteases and Endoproteases

Abstract: Large portions of rice bran protein cannot be solubilized by mild solvents, but endoprotease use increases protein recovery. Bran was treated with 2 commercial proteases to achieve 8% to 9% peptide bond hydrolysis. The exo- plus endprotease was preferred to just using endopeptidases as it allowed the production of protein hydrolysates with enhanced functional properties. Solubility and emulsification activity and stability of hydrolysates produced with the protease blends were greater than that produced with endoprotease alone. These high value hydrolysates, produced from rice bran, an underutilized rice milling coproduct, are suitable for many processed foods, particularly those requiring potent solubility and emulsification at mildly acidic conditions.

Textural, Water Holding, and Sensory Properties of Low‐fat Pork Bologna with Normal or Waxy Starch Hull‐less Barley

Abstract: All ultra-low-fat (< 1%) pork bolognas had similar cook yield and composition. Addition of 4% hull-less waxy barley flour or meal to formulations provided the greatest purge control; 4% normal starch barley, wheat flour and potato starch were intermediate; 0.25% kappa-carrageenan or 1% soy protein concentrate had little effect on water holding and texture. Expressible moisture and purge were significantly correlated to moisture content and batter viscosity. Formulations with wheat flour and waxy barley meal were scored the firmest, while bologna with potato starch required the most force to compress. For most sensory properties, barley fractions performed similarly

Inactivation Kinetics of Foodborne Spoilage and Pathogenic Bacteria by Ozone

Abstract: Ozone was tested against Pseudomonas fluorescens, Escherichia coli O157:H7, Leuconostoc mesenteroides, and Listeria monocytogenes. When kinetic data from a batch reactor were fitted to a dose-response model, a 2-phased linear relationship was observed. A continuous ozone reactor was developed to ensure a uniform exposure of bacterial cells to ozone and a constant concentration of ozone during the treatment. Survivors plots in the continuous system were linear initially, followed by a concave downward pattern. Exposure of bacteria to ozone at 2.5 ppm for 40 s caused 5 to 6 log decrease in count. Resistance of tested bacteria to ozone followed this descending order: E. coli O157:H7, P. fluorescens, L. mesenteroides, and L. monocytogenes.

Quality Changes in Fresh-cut Pear Slices as Affected by Cultivar, Ripeness Stage, Fruit Size, and Storage Regime

Abstract: Fresh-cut fruit slices prepared from partially ripened Bartlett pears had longer shelf life than those from Bosc, Anjou, and Red Anjou pears. Pear fruit ripeness, based on flesh firmness of 44 to 58 N, is optimal for fresh-cut pear slice processing. Pear slices derived from smaller size fruit (122 to 135 g) have greater cut surface discoloration and deteriorate more rapidly than slices derived from larger fruit (152 g). Recently harvested Bartlett pear fruit and whole pears held at -1 °C in a controlled atmosphere of 2%O 2 + 98%N 2 had a longer post-cutting shelf life than those held in air at -1 °C for the same duration. Cut surface browning, flesh softening, and surface dehydration of the slice cut surface were all contributors to loss of product quality.

Influence of NaCl and CaCl2 on Cold‐Set Gelation of Heat‐denatured Whey Protein

Abstract: Heat-denatured whey-protein isolate (HD-WPI) solutions were prepared by heating a 10 wt% WPI solution (pH 7) to 80°C for 10 min and then cooling it back to 30 °C. Cold-set gelation was initiated by adding either NaCl (0 to 400 mM) or CaCl 2 (0 to 15 mM). Both salts increased the turbidity and rigidity of the HD-WPI solutions. Gelation rate and final gel strength increased with salt concentration and were greater for CaCl 2 than NaCl at the same concentration because the former is more effective at screening electrostatic interactions and can form salt bridges.