Microencapsulation by Spray Drying of Multiple Emulsions Containing Carotenoids

ABSTRACT: Water-in-oil-in-water (W1/O/W₂) multiple emulsions with 25% and 35% solids contents were spray-dried producing microcapsules with 3.9:1, 2.6:1, and 1.4:1 biopolymers blend to primary emulsion ratios and 0.25% (w/w) theoretical carotenoids concentration. Microcapsules with better morphology, encapsulation efficiency, and larger particle size were those obtained from higher biopolymers blend to primary emulsion ratios and solids content, but showed relatively higher carotenoids degradation kinetics than microcapsules made with lower biopolymers blend to primary emulsion ratios and solids content, which exhibited poorer morphology, encapsulation efficiency, and smaller particle size. Microcapsules stored at different water activities showed maximum carotenoids degradation at a water activity (a_w) of 0.628, with lower carotenoids degradation occurring at lower or higher a_w.     

Whey Protein Film Composition Effects on Potassium Sorbate and Natamycin Diffusion

ABSTRACT: To assess the ability of whey protein films to act as antimicrobial carriers, the effect of film composition on preservative diffusion was investigated. Preservative diffusion coefficients were measured at 24°C in whey protein isolate (WPI) films with different WPI-glycerol plasticizer ratios (1:1 to 15:1), beeswax (BW) content, 0% to 40% w/w dry solids, and preservative addition of 0.3% (w/w) natamycin or 1.6% (w/w dry solids) potassium sorbate. Diffusion coefficients for potassium sorbate and natamycin were in the ranges 1.09 × 10⁻¹¹ to 13.0 × 10⁻¹¹ m²/s and 6.16 × 10⁻¹⁴ to 37.8 × 10⁻¹⁴ m²/s, respectively, and significantly decreased as the WPI-glycerol ratio increased. No significant difference in sorbate diffusion was seen with the addition of BW.     

Rheology and Oxidative Stability of Whey Protein Isolate-Stabilized Menhaden Oil-in-Water Emulsions as a Function of Heat Treatment

ABSTRACT:  Menhaden oil-in-water emulsions (20%, v/v) were stabilized by 2 wt% whey protein isolate (WPI) with 0.2 wt% xanthan gum (XG) in the presence of 10 mM CaCl₂ and 200 μM EDTA at pH 7. Droplet size, lipid oxidation, and rheological properties of the emulsions were investigated as a function of heating temperature and time. During heating, droplet size reached a maximum at 70 °C and then decreased at 90 °C, which can be attributed to both heating effect on increased hydrophobic attractions and the influence of CaCl₂ on decreased electrostatic repulsions. Combination of effects of EDTA and heat treatment contributed to oxidative stability of the heated emulsions. The rheological data indicate that the WPI/XG-stabilized emulsions undergo a state transition from being viscous like to an elastic like upon substantial thermal treatment. Heating below 70 °C or for less than 10 min at 70 °C favors droplet aggregation while heating at 90 °C or for 15 min or longer at 70 °C facilitates WPI adsorption and rearrangement. WPI adsorption leads to the formation of protein network around the droplet surface, which promotes oxidative stability of menhaden oil. Heating also aggravates thermodynamic incompatibility between XG and WPI, which contributes to droplet aggregation and the accumulation of more WPI around the droplet surfaces as well.     

Quality changes in fresh-cut Fuji apple as affected by ripeness stage, antibrowning agents, and storage atmosphere

ABSTRACT:  The effect of ripening state, modified atmosphere, and the use of antibrowning agents was investigated in an attempt to determine optimum ripeness and processing conditions for extending the shelf-life of fresh-cut Fuji apple. Apples were classified in 3 groups: mature-green, partially ripe, and ripe; after peeling and slicing, fruits were treated with 1% (w/v) N -acetylcysteine, or 1% (w/v) ascorbic acid (control), and then packed into polypropylene trays with air or a gas mixture (2.5% O₂+ 7% CO₂+ 90.5% N₂) and sealed. Trays containing the apple slices were stored in darkness at 4 °C ± 1 °C and analyzed periodically during 43 d. Changes in atmosphere composition, color, and firmness were examined. Partially ripe apples, based on their lower ethanol production and maintenance of their original color and firmness, were the most suitable to prepare the fresh-cut commodities. A postcutting dip in 1% (w/v) N -acetylcysteine was the most effective treatment to prevent cut surface browning and preserve the initial appearance of Fuji apple slices during more than 1 mo at 4 °C. Low O₂ and elevated CO₂ (2.5% O₂+ 7% CO₂) atmosphere extended the shelf life of apple slices because of a significant inhibition of ethylene production.     

Reduction of Streptococcus thermophilus in a whey protein isolate by low moisture extrusion cooking without loss of functional properties

A whey protein isolate powder (WPI) (4–5% water) inoculated with 5x10⁵ viable Streptococcus thermophilus per g, was continuously processed in a twin screw extruder under the following conditions (barrel length = 500 or 1000 mm; screw profile = forward transport and compression elements; moisture content during extrusion = 4–5%; feed rate = 10 kg h^-1; barrel temperature ( T_b ) = 80–204°C; speed of screw rotation = 50 r.p.m.). The minimum residence time determined by pulse injection of erythrosin was 20–25 s (500 mm barrel) or 35–40 s (1000 mm barrel).
Reduction values of viable Streptococcus thermophilus of 10^4.2-fold (500 mm barrel, T_b = 143°C) or 10^4.9-fold (1000 mm barrel, T_b = 133°C) were obtained without any modification of protein solubility or gelling properties. WPI extruded at the highest barrel temperatures (182–204°C) underwent limited browning and reduction of protein solubility. Gel permeation and hydrophobic interaction chromatography of the soluble constituents did not show any aggregates of β-lactoglobulin or α-lactalbumin.
Gels prepared from control or extruded WPI ( T_b 143°C with a barrel length = 500 mm or T_b 133°C with a barrel length = 1000 mm) were identical, as judged by scanning electron microscopy and rheological evaluations.     

Preparation and Characterization of Whey Protein Film Incorporated with TiO2 Nanoparticles

ABSTRACT:  Biodegradable titanium dioxide (TiO₂)/whey protein isolate (WPI) blend films were made by casting denatured WPI film solutions incorporated with TiO₂ nanoparticles. X-ray diffraction, UV-vis spectra, and fluorescence spectra of the films showed the successful incorporation of TiO₂ nanoparticles into the WPI matrix and indicated the interactions between TiO₂ and WPI. Mechanical tests revealed the antiplasticizing effect of TiO₂ nanoparticles on the WPI/TiO₂ film. Small amounts (<1 wt%) of added TiO₂ nanoparticles significantly increase the tensile properties of WPI film, but also decrease the moisture barrier properties. The addition of higher amounts (>1 wt%) of TiO₂ improves moisture barrier properties but lowers the tensile properties of the film. Microstructural evaluation confirmed the aggregation and distribution of TiO₂ nanoparticles within the WPI matrix and validated the results of functional properties of the WPI/TiO₂ film.     

Comparison of Gum Arabic, Modified Starch, and Whey Protein Isolate as Emulsifiers: Influence of pH, CaCl2 and Temperature

ABSTRACT: The particle size and zeta potential of model beverage emulsions (0.01 wt% soybean oil-in-water emulsions, d ≅ 1 mm) stabilized by gum arabic, modified starch, or whey protein isolate (WPI) were studied with varying pH (3 to 9), CaCl₂ concentration (0 to 25 mM), and temperature (30 °C to 90 °C). Temperature, pH, CaCl₂ strongly influenced emulsions stabilized by WPI because its stabilizing mechanism was mainly electrostatic repulsion, but not those stabilized by gum arabic or modified starch because their stabilizing modes of action were mainly steric repulsion. This study may have important implications for the application of WPI as an emulsifier in beverage emulsions.     

Antimicrobial effect of electrolyzed oxidizing water against Escherichia coli O157:H7 and Listeria monocytogenes on fresh strawberries (Fragaria x ananassa)

ABSTRACT:  Antibacterial activity of electrolyzed oxidizing (EO) water prepared from 0.05% or 0.10% (w/v) sodium chloride (NaCl) solutions against indigenous bacteria associated with fresh strawberries ( Fragaria × ananassa ) was evaluated. The efficacy of EO water and sodium hypochlorite (NaOCl) solution in eliminating and controlling the growth of Listeria monocytogenes and Escherichia coli O157:H7 inoculated onto strawberries stored at 4 ± 1 °C up to 15 d was investigated at exposure time of 1, 5, or 10 min. Posttreatment neutralization of fruit surfaces was also determined. More than 2 log₁₀ CFU/g reductions of aerobic mesophiles were obtained in fruits washed for 10 or 15 min in EO water prepared from 0.10% (w/v) NaCl solution. Bactericidal activity of the disinfectants against L. monocytogenes and E. coli O157:H7 was not affected by posttreatment neutralization, and increasing exposure time did not significantly increase the antibacterial efficacy against both pathogens. While washing fruit surfaces with distilled water resulted in 1.90 and 1.27 log₁₀ CFU/mL of rinse fluid reduction of L. monocytogenes and E. coli O157:H7, respectively, ≥ 2.60 log₁₀ CFU/mL of rinse fluid reduction of L. monocytogenes and up to 2.35 and 3.12 log₁₀ CFU/mL of rinse fluid reduction of E. coli O157:H7 were observed on fruit surfaces washed with EO water and NaOCl solution, respectively. Listeria monocytogenes and E. coli O157:H7 populations decreased over storage regardless of prior treatment. However, EO water and aqueous NaOCl did not show higher antimicrobial potential than water treatment during refrigeration storage.     

Incorporation of the Antilisterial Bacteriocin-like Inhibitory Substance from Pediococcus parvulus VKMX133 into Film-forming Protein Matrices with Different Hydrophobicity

ABSTRACT: The antilisterial bacteriocin-like inhibitory substance (BLIS) produced by Pediococcus parvulus VKMX133 was incorporated into protein film matrices of ethanol-soluble corn zein (CZ), and water-soluble whey protein isolate (WPI). Various BLIS concentrations were added to film-forming solutions (FFS), cast, dried, and cut in circular sections (28.27 mm²). Antimicrobial activity of films was evaluated by measuring inhibition zones against Listeria innocua ATCC 33090 on tryptic soy broth (TSB) agar. BLIS released from films into water at 10 °C was determined. Film effectiveness was evaluated by measuring the reduction of L. innocua population (10⁸ colony-forming units [CFU]/mL) in peptone water where film sections were immersed. Film topography was analyzed by scanning electron microscopy (SEM). The minimum BLIS concentration in FFS to generate films with antimicrobial activity was 833 and 3333 arbitrary units per milliliter (AU/mL) for CZ and WPI, respectively. BLIS released into water was detected only for CZ films. Antimicrobial CZ films were more effective in reducing L. innocua population than WPI films at the same BLIS concentrations. SEM showed that surface topography was porous for CZ and more closed and compact for WPI films. BLIS can be entrapped into film protein matrices to produce edible antimicrobial packaging. However, BLIS inhibitory action against L. innocua and release were dependent on film nature and topography, and probably on hydrophobic and electrostatic interactions arising between the protein matrices and BLIS. High concentration of bacteriocin in films does not necessarily improve their effectiveness against L. innocua.     

Antimicrobial Effects of Lactoferrin, Lysozyme, and the Lactoperoxidase System and Edible Whey Protein Films Incorporating the Lactoperoxidase System Against Salmonella enterica and Escherichia coli O157:H7

Lactoferrin (LF), lysozyme (LZ), the lactoperoxidase system (LPOS), and edible whey protein isolate (WPI) films incorporating LPOS were studied for inhibition of Salmonella enterica and Escherichia coli O157:H7. Antimicrobial effects of LF (5 to 40 mg/mL), LZ (1 to 20 mg/mL), and LPOS (0.5% to 5.0% [w/v] [0.03–.25 g/g, dry basis]) were examined by measuring turbidity of antimicrobial‐containing media after inoculation and by examining cell inhibition by WPI films incorporating LPOS (LPOS‐WPI films) on an agar recovery medium. Elastic modulus (EM), tensile strength (TS), percent elongation (%E), oxygen permeability (OP), and Hunter L, a and b of WPI films incorporating 0.03 to 0.25 g/g of LPOS were compared with those of plain WPI films without LPOS. The growth of S. enterica and E. coli O157:H7 (4 log colony‐forming units [CFU]/mL) in tryptic soy broth (TSB) was not prevented by LF at ≥20 and ≥40 mg/mL, respectively. S. enterica and E. coli O157:H7 in TSB were not inhibited by LZ at ≥ 6 and ≥ 20 mg/mL, respectively. LPOS at concentrations of 2.75% (w/v) and 1.0% (w/v) reduced S. enterica and E. coli O157:H7 to below the limit of detection (1 CFU/mL) in TSB, respectively. LPOS‐WPI films (0.15 g/g) completely inhibited S. enterica and E. coli O157:H7 (4 log CFU/cm²), inoculated either onto agar before placing the film disc or onto top of the film disc. Incorporation of 0.25 g/g of LPOS decreased EM, TS, and %E. The oxygen barrier property of WPI films was improved with the incorporation of LPOS at 0.15 to 0.25 g/g.     

Modified atmosphere packaging of shredded lettuce

A retail package system was used to study the atmosphere modification which developed within packages of shredded Iceberg lettuce, sealed in trays with a range of polymer films of different gas permeabilities (oxygen permeability of 3000 to 10,000 ml/m²/day/atm. at 25°C). Modified atmospheres were produced both naturally by respiration, and by application of gas flushing techniques.
The effects of these modified atmosphere conditions on visual and sensory quality of shredded lettuce was observed by monitoring colour change and development of off-odours. An equilibrated modified atmosphere containing 1–3% O₂ and 5–6% CO₂was established with 35 um low density polyethylene film after flushing with 5% O2, 5% CO₂ in N₂. This resulted in a shelf-life of approximately 14 days at 5°C, almost double that of the controls.     

Some effects of modified-atmosphere packaging and vacuum packaging in combination with antioxidants on quality and storage life of chilled potato strips

A modified-atmosphere packaging system for chilled fresh potato strips, which rapidly produced oxygen levels < 3%, was identified. This system enclosed the strips within 25 μ low density polyethylene film heat sealed to a fibre tray lined with Surlyn-PVdC-Surlyn, and the package flushed with an initial atmosphere of 5% O₂, 10% CO₂. An equilibrium-modified atmosphere of 3–4% CO₂, 1–2% O₂ was established after 3 days' storage at 5°C. This modified-atmosphere package, used in combination with dipping of potato strips in a 10% ascorbic acid solution, inhibited enzymatic discoloration for 1 week at 5°C. Vacuum packaging within a Surlyn/PVdC-coated polyester film, with or without dipping in ascorbic acid solution, inhibited discoloration of chilled potato strips stored at 5°C for at least 2 weeks.     

Optimization of Medium Composition for Cultivating Clostridium butyricum with Response Surface Methodology

ABSTRACT: Probiotic bacteria, such as some strains of Clostridium butyricum , have been frequently used as the active ingredient in functional foods. However, slow growth of the probiotic bacteria has been one of the big concerns for their potential commercial application. In the present study, a fractional factorial design was applied to investigate the main factors, namely, the concentrations of the glucose, tryptone, yeast extract, beef extract, cys-teine, (NH₄) ₂SO₄, NaCl, K₂HPO₄, and the medium initial pH that affected the growth of 1 probiotic strain, C. butyricum ZJUCB, currently preserved in our laboratory. Central composite experimental design and response surface methodology were adopted to derive a statistical model for optimizing the composition of the medium. The experimental results showed that the optimum medium for incubating the C. butyricum ZJUCB was composed of 2.44% (w/v) glucose, 2.08% yeast extract (w/v), 1% tryptone (w/v), 0.1% (NH₄)₂SO₄ (w/v), 0.1% NaHCO₃ (w/v), 0.02% MnSO₄. H₂O (w/v), 0.02% MgSO₄. 7H₂O (w/v), 0.002% CaCl₂ (w/v), and 2% agar (w/v) (if necessary) at pH 8.55. After incubation for 24 h in the optimum medium, the populations of the viable organisms could reach 10⁹ colony-forming units (CFU)/mL, which was 100 times higher than that incubated in the initial medium.     

Improved Firmness in Calcified Diced Tomatoes by Temperature Activation of Pectin Methylesterase

ABSTRACT: The effects of temperature and calcium on pectin methylesterase (PME) activity and texture in tomato pericarp material were examined. Heating thin slices of pericarp to temperatures between 50°C and 75°C led to the rapid evolution of methanol from the material, indicating an activation of PME. This activity was further stimulated when CaCl₂ (up to 2.0% w/v) was added. When applied to half-inch diced tomato pericarp, the same conditions that led to the activation of PME also improved firmness. Diced tomatoes treated for 5 min with 0.5% CaCl₂ at 70°C were 2.5 times firmer than diced tomatoes treated with CaCl₂ at room temperature. This improvement in texture by treating with CaCl₂ at elevated temperatures was only apparent when the tomatoes received a subsequent 100°C treatment. Heating tomatoes to 70°C either before or after the CaCl₂ treatment also improved firmness through a subsequent high-temperature treatment, but to a lesser extent than heating during the CaCl₂ treatment. These results are consistent with the model that heating to 70°C greatly increases PME activity, leading to extensive pectin de-esterification and increased calcium cross-linking of the pectins in the middle lamella. Production of thermally processed diced tomatoes with improved firmness should be possible by increasing the temperature during and after calcium treatment.     

Maintaining Quality of Fresh-cut Tomato Slices through Modified Atmosphere Packaging and Low Temperature Storage

ABSTRACT: Quality of fresh-cut tomato slices was compared during cold storage under various modified atmosphere packaging conditions. Chilling injury of slices in containers sealed with Film A was higher than with Film B; these films had oxygen transmission rates of 87.4 and 60.0 ml · h^-1· m^-2· atm^-1 at 5 °C and 99% RH, respectively. While slices in containers with an initial atmospheric composition of air, 4% CO₂+ 1 or 20% O₂, 8% CO₂+ 1 or 20% O₂, or 12% CO₂+ 20% O₂ showed fungal growth, slices in containers with 12% CO₂+ 1% O₂ did not. Low ethylene in containers enhanced chilling injury. Modified atmosphere packaging provided good quality tomato slices with a shelf life of 2 w or more at 5 °C.     

Desulfiting Dried Apricots by Hydrogen Peroxide

ABSTRACT: Removal of sulfites from excessively sulfited dried apricots using hydrogen peroxide (H₂O₂) was studied. Dried apricots were dipped into 0.5, 1.0, and 1.5% H₂O₂ solutions at 20 °C and 40 °C for various times. At 60 °C, apricots were also treated with 1% H₂O₂ solution. Removal of sulfites by H₂O₂ followed a 1st-order kinetic model. At 20 °C to 60 °C and 1% H₂O₂ concentration, the E_a value was 22.46 kJ mol⁻¹. H₂O₂ treatment caused lighter, more yellow, and less red dried apricots. Critical factors for H₂O₂ application are choosing the appropriate H₂O₂ concentration, temperature, and exposure time and without bleaching the natural color of dried apricots.     

Stabilization and Partial Purification of a Protease from Ginger Rhizome (Zingiber offinale Roscoe)

ABSTRACT: Ginger protease (GP) or zingibain is of interest as a meat tenderizing agent. The objective of this research was to investigate food-compatible methods for stabilizing GP during storage or enzyme fractionation. Crude GP extracted from fresh ginger had a half-life (t_1/2) of 2.1 (±0.16) d at 5°C decreasing to 20 min at 30°C. Addition of ascorbate (0.2% w/v) increased the t_1/2 for GP from 2 to 20 d at 5°C. Dithiothreitol or Ethylenediaminetetraacetic acid (EDTA) had no effect on GP stability. Acetone powder preparations from ginger yielded GP with t_1/2 of 18 mo at 5°C. Crude GP extracted from acetone powder was sufficiently stabilized to allow fractionation by ion exchange chromatography without the addition of toxic or expensive additives. GP was partially purified 252-fold with a recovery of 61%. The nomimal molecular weight of GP was 34.8 kDa compared with 25.1 kDa for papain. This work shows that the stability of GP can be greatly improved, increasing its attractiveness as a commercial product. Some possible routes of GP deactivation and stabilization are discussed.     

Purification and Characterization of an α-L-Rhamnosidase from Aspergillus terreus of Interest in Winemaking

ABSTRACT: An enzyme with α-L-rhamnosidase activity was purified to homogeneity from a culture filtrate of Aspergillus terreus after growth in a medium containing L-rhamnose as the sole carbon source. The biosynthesis of this enzyme was repressed by glucose. The enzyme had a molecular mass of 96 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point of 4.6 as determined by analytical isoelectric focusing. The pH and temperature optima for the enzyme were found to be 4.0 and 44 °C, respectively. Using p-nitrophenyl-α-L-rhamnopyranoside as a substrate, the enzyme exhibited Michaelis-Menten kinetics with K_M and V_max values of 0.17 mM and 84 U/mg, respectively. The enzyme was inhibited competitively by L-rhamnose (K₁ 2.5 mM). Divalent cations such as Ca²⁺ Mg²⁺ Zn²⁺ and Co²⁺ stimulated the a-L-rhamnosidase activity, whereas this was inhibited by Hg2+ and Cd2+. Ethanol (12% v/v) and glucose (21% w/v) decreased enzyme activity by approximately 20%, while this was not affected by SO₂.     

Fate of Aflatoxin M1 during Manufacture and Storage of Feta Cheese

ABSTRACT:  The effect of feta cheese manufacture on aflatoxin M₁ (AFM₁) content was studied using an enzyme immunoassay technique. Feta cheese was made from milk spiked with 1 and 2 μg AFM₁ per kilogram milk. Pasteurization at 63 °C for 30 min caused <10% destruction of AFM₁. During cheese making, the remaining AFM₁ in milk was partitioned between curd and whey with two-thirds retained in the curd and one-third going into the whey. Cheeses were then stored for 2 mo in 8%, 10%, and 12% brine solutions at 6 and 18 °C. There was a 22% to 27% reduction of AFM₁ during the first 10 d of storage, with slightly more loss as salt concentration increased and when the cheese was stored at 18 °C. Further storage caused only slight decrease in AFM₁ and after 30 d of brining there was no difference in AFM₁ content of the cheese based upon salt concentration of the brine. At 18 °C, no further losses of AFM₁ occurred after 30 d, and at 6 °C, there was continued slight decrease in AFM₁ levels until 50 d. After 60 d of brining, there was a total loss of 25% and 29% of the AFM₁ originally present for cheese brined at 6 and 18 °C, respectively. Thus, the combination of pasteurization, conversion of milk into feta cheese, and at least 50 d storage of cheese in brine caused a total loss of about 50% of the AFM₁ originally present in the raw milk.     

Modified atmosphere packaging of broccoli florets

A retail packaging system was used to study the atmosphere modification which developed within sealed packages of prepared broccoli florets with a range of polymer films of different gas permeabilities (oxygen permeability 3000–32,500 ml/m²/day/atm). Three methods of sealing were investigated and modified atmospheres (MA) were produced both naturally by respiration and by application of gas flushing techniques. The effects of these MA conditions on sensory quality were observed by monitoring colour change and development of off-odours. A 2–3% O₂, 2–3% CO₂ equilibrium MA was established using LF film to package broccoli florets when stored at 5°C. This, the only consistently aerobic MA attained, did not markedly improve retention of quality of broccoli florets when compared with broccoli stored in air. When broccoli florets were packaged with films which resulted in very low O₂ atmospheres (1% or less) foul of-odours shortened broccoli storage life.