Physicochemical characteristics of soybean oil, palm kernel olein, and their binary blends

Soybean oil (SBO), palm kernel olein (PKO) and their binary blends (containing 5–40% PKO) were studied for their physicochemical characteristics. Decreases in band absorbencies of the resultant Fourier transform infrared spectra were observed in regions attributable to vibrations of the functional groups of unsaturated fatty acids, mainly the =C–H cis stretching at 3009 cm⁻¹and –C=C cis stretching at 1657 cm⁻¹. The solid fat content was measurable in the blends containing 15–40% PKO at 5 and 10 °C, ranging within 4–20% and 2–13%, respectively. The differential scanning calorimetry melting curve for SBO exhibited more complex transition peaks, suggesting a     polymorphic transformation when compared with PKO with a simpler     . Blending of SBO with PKO reduced the complexity caused by the polymorphic transformation, featuring the endotherms that only related to the β' fat crystals.     

THE RHEOLOGICAL CONDITIONS ASSOCIATED WITH JUDGEMENT OF POURABILITY AND SPREADABILITY OF SALAD DRESSINGS

A panel of 25 students compared the pourability and spreadability of two commercial brand salad dressings (non-Newtonian) and a CMC-sugar solution (Newtonian). Correlation of their responses with visco-metric data for the 3 samples indicated that the shear stress and shear rate associated with the sensory evaluation of these two properties are 190–430 dyne cm⁻² and 0.9–6.3 s⁻¹, and < 190 dyne cm⁻² and < 0.9⁻¹, respectively.     

DECONTAMINATION OF A MULTILAMINATED ASEPTIC FOOD PACKAGING MATERIAL AND STAINLESS STEEL BY OZONE

A multilaminated aseptic food packaging material and stainless steel were treated with ozone to inactivate natural contaminants, bacterial biofilms and dried films of Bacillus subtilis spores and Pseudomonas fluorescens. Sterility of the multilaminated packaging material was achieved when 1.0 x 2.0 cm-pieces of the naturally-contaminated material were treated with ozone in water (5.9 μg/mL) for 1 min. Dried films of spores (10⁸/6.3–cm² surface) were eliminated by 13 μg/mL of ozone in water for the multilaminated packaging material and 8 μg/mL in case of the stainless steel. Ozone inactivated Pseudomonas fluorescens in biofilms more effectively on stainless steel than on the multilaminated packaging material. Repeated exposure to ozone of Pseudomonas fluorescens in biofilms on the multilaminated packaging material eliminated up to ∼10⁸ cfu/12.5 cm². In conclusion, ozone is an effective sanitizer with potential applications in the decontamination of packaging materials and equipment food-contact surfaces.     

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.     

Influence of particle size fractions on the physicochemical properties of maize flour and textural characteristics of a maize-based nonfermented food gel

The physicochemical properties of fractionated maize flour and the textural characteristics of a maize-based nonfermented food gel (maize tuwo ) prepared from the respective fractionated flours were evaluated. The maize flour was fractionated into four fractions: <75 μm, 75–150 μm, 150–300 μm, 300–425 μm and whole meal (<425 μm). There were variations in the selected chemical constituents of fractionated maize flour including protein (2.9–4%), ash (0.80–0.97%), crude fibre (0.73–0.91%) and damaged starch (10.1–17.4%). The fractionated maize flour gave variable bulk density (0.80–0.93 g cm⁻³), water absorption capacity (1.9–2.1 g g⁻¹) and oil absorption capacity (1.7–2.1 g g⁻¹). The colour characteristics of the fractionated maize flour and the pasting properties were all affected by the fractionation. The cohesiveness index (strain at peak compressive force) of the food gel from the flour fractions ranged between 15% and 19.5% while the softness index of the food gel ranged between 16.7 and 17.5 mm. The relative high cohesiveness and softness indexes (i.e. 19.5% and 17.4 mm respectively) of maize tuwo prepared from the flour fraction of 75–150 μm can predispose the food gel towards easier hand-mouldability and swallowability respectively; being important quality indicators for its acceptability.     

Modified atmosphere packaging to extend the shelf life of tomatoes

An experimental retail packaging system was used to compare the atmospheric com-position and relative humidity which developed within packs sealed with a range of plastic films with different permeability properties, and to study the effects of these conditions on the rate of ripening (as indicated by colour change) and sensory quality of tomatoes. In packs sealed with several polyvinylchloride (PVC) films or with K-resin (a butadiene-styrene copolymer), an atmosphere containing 3–9% CO₂+3−9% 0₂ developed within circa 3–4 days at 10 or 12.5°C. Ripening of part ripe fruit was retarded, but continued normally after the packs were perforated, with no obvious adverse effects on the smell, flavour or texture of the fruit. In packs sealed with less permeable films (e.g. cellulose acetate), the internal atmosphere equilibrated to 10–18% CO₂+ < 2% O₂, resulting in complete inhibition of ripening, a high incidence of rotting and tainting of the fruit. Very high (98% or above) relative humidity within sealed packs also encouraged fungal spoilage. The possible commercial applications and benefits of this type of modified atmosphere (MA) packaging are discussed.     

丰年虫卵壳色素的制备及稳定性与体外抗氧化活性研究

利用超声波辅助乙醇溶液提取丰年虫卵壳色素,采用红外光谱对色素结构进行初步鉴定,通过紫外-可见扫描光谱分别研究光照、温度、pH值、食品添加剂、金属离子及氧化还原剂对色素稳定性的影响,分别测定色素的总抗氧化能力、羟自由基（·OH）与2,2’-联氮-二（3-乙基-苯并噻唑-6-磺酸）二铵盐自由基（2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) free radical,ABTS＋·）清除活性,以考察色素体外抗氧化活性。结果表明：丰年虫卵壳色素为黑褐色粉末,可能由一类含有羟基、烷烃-CH2、碳碳三键及醚键的酰胺-芳香族复合物组成,其提取液在397 nm波长处获得最大吸收峰。色素对光和高温敏感,pH值变化、蔗糖、碳酸钠、碳酸氢钠、柠檬酸钠、Na＋及K＋对色素稳定性影响较小,苯甲酸钠、Ca2＋、Zn2＋、Fe3＋、Fe2＋、Cu2＋及Pb2＋则对色素均具有一定程度的破坏,酸性条件、柠檬酸、酒石酸、可溶性淀粉、Mg2＋及Al3＋则对色素具有增色效应。丰年虫卵壳色素容易被氧化剂破坏,但具有较高的耐还原性和良好的体外抗氧化活性,清除·OH与ABTS＋·的IC50分别为6.104、0.377 mg/mL。说明该色素可作为天然添加剂应用于食品中,起到一定的抗氧化作用。     

Effect of film and temperature on the sensory, microbiological and nutritional quality of minimally processed cauliflower

The effect of atmosphere modification, generated using three different packaging films, on the quality of cauliflower minimally processed when stored at 4 or 8 °C for up 20 days was evaluated. The colour, texture, weight loss, sensory attributes, as well as microbial counts and sugars and ascorbic acid content were determined. The atmosphere generated with the perforated polyvinylchloride (PVC) film was hardly modified, whereas the other two films (non-perforated PVC and polypropylene films) originated changes in CO₂ and O₂ levels during storage. The different packaging conditions and storage temperature influenced yellowing. An increase in shear force was observed. Weight losses were below 5%. Mesophiles and Pseudomonas counts were below 7 log CFU g⁻¹, the populations being lower with film B and film C than with film A. Cauliflower maintained an acceptable appearance in all the films studied. Total sugars decreased about 27% after 20 days of storage, whereas ascorbic acid did not change.     

EFFECT OF FILMS OF DIFFERENT OXYGEN TRANSMISSION RATE ON TOXIN PRODUCTION BY CLOSTRIDIUM BOTULINUM TYPE E IN VACUUM PACKAGED COLD AND HOT SMOKED TROUT FILLETS

Studies were done to determine the effect of film oxygen transmission rate (OTR) on the time to toxicity in vacuum packaged cold and hot smoked rainbow trout fillets challenged with C. botulinum type E (10² spores/g) and stored at refrigerated conditions (4C), and under mild (8C) and moderate (12C) temperature abuse conditions. While no samples were toxic at 4C, toxin was detected within 28 days at 8C for cold smoked trout fillets vacuum packaged in films with high OTR. Toxin was also detected for most vacuum packaged hot smoked trout fillets within 14–28 days at 8C, with the exception of trout fillets packaged in films with an OTR > 10,000 cc/m²/day. In most cases at 8C, spoilage, based on odor/color scores, preceded or occurred simultaneously with toxigenesis. At 12C all cold and hot smoked trout were toxic after 14–21 days and samples packaged in films with an OTR <5000 cc/m²/day became toxic before, or at the same time as, samples became spoiled. This study has shown that vacuum packaging of trout fillets in low gas barrier films, ranging in OTR from approximately 3,000 to approximately 10,000 cc/m²/day at 24C and 0% relative humidity (RH), did not prevent the growth and toxin production by C. botulinum in vacuum packaged cold and hot smoked trout fillets at 12C. Additional barriers, other than the OTR of the packaging film, need to be considered to ensure the safety of vacuum packaged trout fillets, particularly at mild to moderate temperature abuse storage conditions.     

ANTIMICROBIAL PROPERTIES OF NISIN-COATED POLYMERIC FILMS AS INFLUENCED BY FILM TYPE AND COATING CONDITIONS

Polymeric films were coated with nisin, an antimicrobial peptide, for potential application in shelf-life extension of food. Five commercial packaging films with varying surface energies were compared. The highest antimicrobial activity was observed on the most hydrophobic nisin-coated films (surface energy ± 32 dyne/cm). The binding affinity of nisin to the surface of ethylene acrylic acid copolymer (surface energy = 32 dyne/cm) was investigated. Films were coated in nisin solutions under varying conditions including nisin concentration, contact time, solution's volume to film area ratio, pH of coating solution and temperature during coating. Stronger nisin activity was detected on films as the coating time increased from 30 s to 2 h. Higher nisin coating concentration also promoted the binding of nisin to films with saturation level observed at 250 μg/mL. Films coated with nisin using a higher solution to film area ratio (0.84 compared to 0.14 and 0.28 mL/cm²) also exhibited higher nisin activity.     

Extraction of ginger rhizome: kinetic studies with supercritical carbon dioxide

The rates of extraction of [6]-gingerol from ground dried Jamaican ginger rhizomes were determined in supercritical carbon dioxide over the pressure range 128–197 bar (1850–2850 psi) and the temperature range 50–65°C. The CO₂ densities varied from 0.415 to 0.775 g cm⁻³. First-order plots showed two approximately linear sections with an initial intercept. The first linear section corresponded to a relatively fast initial extraction stage while the last 20% or so of the gingerol was extracted in the much slower subsequent stage. Reducing the ginger particle size by a factor of 3 increased the rate constant of the fast stage nine-fold. Despite the low viscosity of the supercritical fluid, the rate constants of the fast stage were much smaller than in extractions with organic solvents. Only when the CO₂ density was increased to 0.775 g cm⁻³ did the rate constant of the fast stage rise to a value comparable with, but still smaller than, those in organic solvents of similar density. The rate constants of the later slow extraction stage were also somewhat smaller than the corresponding values in organic solvents at 30°C.     

Antimicrobial properties of grape seed extracts and their effectiveness after incorporation into pea starch films

Chemical analysis and antimicrobial nature of grape seed extracts (GSE) and their Reisling Vitis vinifera L. application as fortificants for edible starch films were investigated. GSE possessed an antioxidant activity of 17.18 ± 1.29 mmol TROLOX equivalents g_extract⁻¹ and total phenolic content of 327.58 ± 7.24 mmol gallic acid equivalents g_extract⁻¹ mainly attributed to their flavonoid and phenolic acid composition determined by high-performance liquid chromatography accomplished to a diode array detector and a electrospray ionisation mass spectrometer in negative mode (HPLC-DAD/ESI-MS). GSE inhibited the growth of Gram-positive food-borne pathogens while Gram-negatives were not inhibited. After GSE were incorporated into pea starch films, thickness of enriched films increased and the puncture and tensile strength decreased compared to control films. Furthermore, migration of phenolic compounds from the films to different food simulants, aqueous, acidic and alcoholic solution was determined according to 89\109\EEC directive. A higher particle migration in acidic simulants was found. Finally, the effect of GSE incorporated pea starch films was tested in vitro with pork loins infected with Brochothrix thermosphacta. GSE films reduced the bacterial growth in 1.3 log colony forming units mL⁻¹ after 4 days incubation at 4 °C.     

CHARACTERIZATION OF MODEL NITROSYLHEME PIGMENTS WITH VISIBLE, INFRARED AND 15N FOURIER TRANSFORM NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

Synthetic pigments that model the organic-soluble pigment in heat-processed cured ham were characterized with infrared (IR) and ¹⁵N nuclear magnetic resonance (NMR) spectroscopy. The two pigments synthesized were ¹⁵N nitrosyl (protoporphyrinato- IX) iron (II), or Fe^II PP¹⁵ NO, and ¹⁵N dinitrosyl (protoporphyrinato-IX), or Fe^II PP(¹⁵NO)₂. An NMR spectrum was obtained only for the Fe^II PP¹⁵ NO. The NMR spectrum consisted of a single peak + 1.78 ppm from the Na¹⁵ NO³ and –6.8 from the CH₃NO₂ reference. The IR spectrum included a single NO symmetric stretch at 1801 cm⁻¹. The visible spectrum of Fe^II PPNO did not match the visible spectrum of ham extracts, while it did with FE^II PP(¹⁵NO)₂. An unequivocal structural assignment of Fe^II PP¹⁵ NO was made, but longer NMR runs may be necessary to obtain a spectrum and unequivocal structural assignment of Fe^II PP(¹⁵ NO)₂.     

RELEASE OF PROPYL PARABEN FROM A POLYMER COATING INTO WATER AND FOOD SIMULATING SOLVENTS FOR ANTIMICROBIAL PACKAGING APPLICATIONS

The release phenomena of propyl paraben from a polymer coating to water and three food simulating solvents (10% aqueous ethanol, 50% aqueous ethanol, n-heptane) were studied for antimicrobial packaging applications. The effects of food simulating solvent, initial concentration in the coating and temperature on the propyl paraben release were examined. The initial concentration of propyl paraben in the coating ranged from 1.26 × 10⁴ to 10.52 × 10⁴ g/m³ and the temperature from 5.5 to 30C. For water, the release was controlled by Fickian diffusion with constant diffusion coefficient (7±11 × 10^-11 cm²/s at 30C), and independent of the initial concentration. For 10% ethanol, the release followed again the Fickian model with constant diffusion coefficient (30±40 × 10^-11 cm²/s at 30C). For 50% ethanol and n-heptane, the release was instantaneous and not controlled by Fickian diffusion. For the release into water, the activation energy for diffusion from the Arrhenius relationship was around 88 kJ/mole.     

New Kinetic Approach to the Evolution of Polygalacturonase (EC 3.2.1.15) Activity in a Commercial Enzyme Preparation Under Pulsed Electric Fields

ABSTRACT:  The effect of pulsed electric fields (PEF) on polygalacturonase (PG) activity in an aqueous solution of a commercial enzyme preparation was studied. Monopolar square wave pulses of 4 μs were delivered to the solution, which circulated through tubular chambers with 2 stainless steel electrodes in continuous operation. The electric field intensities ( E ) and treatment time ( t ) ranged within 15 to 38 kV cm⁻¹ and 300 to 1100 μs, respectively. Although important reduction of the PG activity could be achieved (up to 76.5% at E = 38 kV cm⁻¹ and t = 1100 μs), the experimental data showed certain enhancement of PG activity under soft conditions (up to 110.9% at E = 15 kV cm⁻¹ and t = 300 μs). A kinetic mechanism involving 2 consecutive irreversible first-order steps was developed to describe and explain the experimental data. The tested model exhibited high accuracy in respect of the experimental data and the error of the model was lower than 4.4%. The kinetic rate constant of the first ( k ₁) and second step ( k ₂), ratio between the activities of intermediate and native forms of the enzyme (Λ), and other quantities related to the model, were obtained within a Bayesian framework. k ₁ resulted independent of the E applied and considerably greater in magnitude order ( k ₁ mean = 6 μs⁻¹) with respect to k ₂, which was dependent on the applied E (mean values ranged from 489E-6 μs⁻¹ at E = 38 kV cm⁻¹ to 1215E-6 μs⁻¹ at 38 kV cm⁻¹). The dependency of k ₂ toward E was described using an exponential relationship.     

Effects of meat piece size and phosphate on maximum slicing rate, cooking loss and sensory quality of a re-formed pigmeat shoulder product

Summary Two pre-tumbling treatment variables (meat piece size; raw product phosphate content) were evaluated for their effects on maximum slicing rate (MSR), cooking loss and sensory quality of a commercially produced, cooked re-formed pigmeat shoulder product. At 0.457% phosphate, incremental reductions in meat piece size which increased specific surface from 0.60 to 0.93 cm² cm⁻³ enabled MSR to increase from 300 to 400 slices min⁻¹, reduced cooking losses from 0.875 to 0.60% and gave a more tender product. At 0.60 cm² cm⁻³ specific surface, increasing phosphate incrementally from 0.457 to 0.532% produced similar positive effects on MSR and cooking loss but at phosphate above 0.482% sensory quality declined. Combination of optimal specific surface (0.93 cm² cm⁻³) and phosphate (0.482%) permitted a MSR of 420 slices min⁻¹, reduced cooking loss to 0.50% and gave an acceptable product. These process modifications can thus be advocated for improved production rate, yield and sensory quality.     

Assessment of the microbiological conditions of red-meat carcasses from bacterial counts recovered by sampling via excision or swabbing with cotton wool

Samples from 240 carcasses were collected from four animal species (porcine, ovine, bovine and equine). Two samples were taken from each carcass, one using the excision method (EX) and the other the wet–dry swabbing method (SW). Eight areas from each carcass were sampled. Most of the samples obtained by SW revealed total aerobic viable counts (TVC) levels of between 3.1 and 4.0 log CFU cm⁻², while most of the values corresponding to excision were located between 4.1 and 5.0 log CFU cm⁻². Moreover, Enterobacteriaceae (EC) counts were only detected above 3.0 log CFU cm⁻² in 0.85% of the carcasses when the samples were collected by swabbing, while the excision method revealed that 13.75% of the carcasses presented EC greater than 3.0 log CFU cm⁻². TVC and EC by EX revealed statistically significant differences compared to SW, while no significant linear relationship was found between carcass surface bacterial counts obtained by SW and EX.     

MICROBIAL STABILIZATION OF INTERMEDIATE MOISTURE FOOD SURFACES I. CONTROL OF SURFACE PRESERVATIVE CONCENTRATION

Changing environmental conditions to which intermediate moisture foods (IMF's) are exposed during production, storage, distribution and use, are important microbial stability factors. Temperature changes result in local surface condensations leading to microbial outgrowth on the surface. An approach to improved surface stability using a high preservative surface concentration maintained by an impermeable edible food coating was developed. Permeability tests predicted that zein was an acceptable coating. Sorbic acid distribution experiments confirmed its barrier properties. Apparent diffusion coefficient was estimated between 3 and 7 × 10⁻⁹ cm²/s. These values were 150–300 times smaller than the value measured in the bulk of the IMF model food system used in this study, 10⁻⁶ cm²/s.     

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.     

Quality of Shredded Carrots as Affected by Packaging Film and Storage Temperature

ABSTRACT: Different packaging films and storage temperatures were used to establish a range of equilibrium modified atmospheres for storage of shredded carrots. Quality and storage-life of the packaged shredded carrots were determined using sensory evaluation, microbial counts, and a range of physical tests. Minimal processing steps such as peeling and shredding caused physical damage, physiological stress, and enhanced microbial growth, leading to a reduced shelf life when compared to the whole vegetable. A P-plus microporous film (CO₂ permeability of 29 X 10³mL.m ^-2.d ^-1.atm ^-1) was the most suitable for the storage of shredded carrots. Findings indicated that deterioration in these products was triggered by the depletion of oxygen more than by the rise in carbon dioxide.