Showing papers in "Innovative Food Science and Emerging Technologies in 2003"

Impact of temperature on lethality and energy efficiency of apple juice pasteurization by pulsed electric fields treatment

Abstract: The applicability of pulsed electric fields as a non-thermal preservation process for liquid food decontamination has been shown in several studies. However, high costs of operation due to the occurrence of a high amount of dissipated electrical energy inhibited an industrial exploitation so far. In this study the focus was put on improving energy efficiency of this process for pasteurization of apple juice inoculated with Escherichia coli by investigating the relation between achieved reduction in survivor count and electric field strength and treatment temperature. An empirical mathematical model was derived to predict the required input of electrical energy for a given inactivation. Using synergistic effects of elevated treatment temperature of 35–65 °C on microbial inactivation the energy consumption could be reduced from above 100 to less than 40 kJ kg−1 for a reduction of 6 log cycles and the need to preheat the juice before treatment provided a possibility to recover the dissipated electrical energy after treatment, leading to a drastic reduction in operation costs. To evaluate the thermal load of the product the pasteurization unit (PU) and the cook value, key benchmarks for the thermal load, were used to compare PEF and conventional heat treatment.

A new process for the combined recovery of pectin and phenolic compounds from apple pomace

Abstract: b ¨¨ Abstract A process for the combined recovery of pectin and phenolic compounds from apple pomace, the primary by-product of apple juice production, was developed. The process includes extraction of dried apple pomace with diluted mineral acid and adsorption of phenolic constituents by a hydrophobic styrene-divinylbenzene copolymerisate. After elution with methanol, the polyphenolics were concentrated in vacuo, stabilised by lyophilisation, and characterised by high-performance liquid chromatography. The predominant compounds were phloridzin, chlorogenic acid and quercetin glycosides. Adsorptive removal especially of oxidised phenolic compounds led to a considerable decolourisation of the pomace extracts, as revealed by determination of L*a*b* values, hue angle and chroma. Gelling properties of pectin were not adversely affected. While the polyphenolics recovered from apple pomace may be used as natural antioxidants or as functional food ingredients, extended fields of application may be obtained for decolorised, refined apple pectins. Furthermore, investigations on the phenolic composition of several New Zealand apple cultivars, of apple seeds, and on the effects of pomace drying on the stability of polyphenolics were carried out. 2002 Elsevier Science Ltd. All rights reserved.

Combined high-pressure and thermal treatments for processing of tomato puree: evaluation of microbial inactivation and quality parameters

Abstract: The effects of combined high-pressure thermal treatments on consistency, viscosity, colour, lycopene content, enzyme activity and micro-organisms were determined, and compared to conventional pasteurisation and sterilisation processes of tomato puree. High-pressure processing at ambient temperature (HPP) improved the colour and viscosity compared to heat pasteurisation, while the water binding capacity and lycopene content were unaffected by HPP. Products treated at 700 MPa, 20 °C resulted in inactivation of the natural flora to a level below the detection limit. After pressure treatment and during chilled storage a increase in viscosity was observed. HPP caused partial inactivation of polygalacturonase (70%), but activation of pectin methylesterase. After high-pressure sterilisation treatments combined with elevated starting temperatures (≥80 °C, HPS, one or two pulses) an ambient stable product was obtained. HPS (one pulse, 700 MPa, 30 s, 90 °C) reduced B. stearothermophilus spore contamination level in inoculated meatballs in tomato puree with at least 4.5 log units. HPS resulted in more than 99% inactivation of polygalacturonase and pectin methylesterase. HPS resulted in a lower viscosity compared to conventional sterilised samples, whereas the water binding capacity was improved. Colour appreciation was improved and lycopene content was retained compared to a 40% loss after conventional sterilisation.

Preparation of high dietary fiber powder from lemon juice by-products

Abstract: Lemon ( Citrus limon cv Fino) juice industry by-products were used to obtain high dietary fiber powder. The effect of processing variables (direct drying, and washing previous to drying) on functional properties, fiber content and type, microbial quality and physicochemical properties of the fiber were evaluated. The obtained fiber powder had good functional, microbial quality and favorable physicochemical characteristics to be used in food formulations. Processing conditions affected fiber composition and properties. Water holding capacity was enhanced by washing (7 g water/g non-washed fiber powder; 12.6 g water/g washed fiber powder) and slightly decreased by the reduction in fiber particle size. Oil holding capacity (6.7 g oil/g fiber powder) was not affected by those factors. Acid detergent and neutral detergent fibers were highest in powder from washed lemon residue (23.73 and 32.91%, respectively). a w was lowest in washed lemon fiber powder (0.13). Washing prevented fiber browning during drying as reflected in color parameters. Washing water rinsed green components. Drying was the responsible for the decrease of bacterial populations (approx. 90% reduction in microbial counts).

Four questions on European consumers’ attitudes toward the use of genetic modification in food production

Abstract: Four questions on European consumers’ attitudes to the use of genetic modification (GM) in food production are posed and answered: (1) how negative are consumer attitudes to GM applications in food production? (2) How do these attitudes affect perception of and preference for products involving GM applications? (3) How deeply rooted are these attitudes? (4) Will the attitudes change due to more information andyor product experience? Drawing on two major studies researching these questions, it is concluded that consumer attitudes towards GM in food production are negative, that these negative attitudes guide the perception of food products involving the use of GM and lead to a range of sweeping negative associations which overshadow potential benefits perceived, that these negative attitudes are embedded in a system of more general attitudes, especially attitude to nature, to technology, and alienation from the marketplace, implying that they are deeply rooted, and that they will not easily be changed by information. They may change, however, due to own experience with products produced using GM and involving clear consumer benefits. 2003 Elsevier Ltd. All rights reserved.

Modeling the combined effect of high hydrostatic pressure and mild heat on the inactivation kinetics of Listeria monocytogenes Scott A in whole milk

Abstract: The survival curves of Listeria monocytogenes Scott A inactivated by high hydrostatic pressure were obtained at four temperatures (22, 40, 45 and 50 °C) and two pressure levels (400 and 500 MPa) in UHT whole milk. Elevated temperatures substantially promoted the pressure inactivation of L. monocytogenes. A 5-min treatment of 500 MPa at 50 °C resulted in a more than 8-log10 reduction of L. monocytogenes, while at 22 °C a 35-min treatment was needed to obtain the same level of inactivation. Tailing was observed in all survival curves, indicating that the linear model was not adequate for describing these curves. The log-logistic model consistently produced best fits to all survival curves and the modified Gompertz model the poorest. The Weibull model produced fits as good as the log-logistic model at the temperature range of 40–50 °C. The Weibull model provided reasonable predictions of inactivation of L. monocytogenes at temperature levels other than the experimental temperatures; however, the log-logistic model was found to be inferior at predicting inactivation.

Electrochemical reactions and electrode corrosion in pulsed electric field (PEF) treatment chambers

Abstract: In Pulsed Electric Field systems for preservation of liquid food, electrochemical reactions can occur in the treatment chamber. This may result in partial electrolysis of the solution, in corrosion of the electrode and in introduction of small particles of electrode material in the liquid. This contribution will describe the phenomena that occur at the electrodes. The ultimate objective is to be able to adapt the design and the pulse waveform such that these phenomena are minimised. After revisiting the basic theory on electrochemical reactions, an equivalent circuit is presented that can be used to model an electrochemical cell. Based on these models it is shown that electrode corrosion can be limited with short enough pulses. The theory has been verified by experiments. The results of these experiments are presented in this contribution.

Frequency and voltage effects on enhanced diffusion during moderate electric field (MEF) treatment

Abstract: Diffusion of beet dye from beet cubes was measured during a 3 min moderate electric field (MEF) process using frequencies ranging from 0 (direct current) to 5000 Hz, and field strengths ranging from 0 (conventional heating) to 23.9 V/cm, while maintaining steady-state temperature at 45 °C throughout the process. Diffusion increased with electric field strength and decreased with frequency. There was no enhanced diffusion from an agar cube or from previously frozen beet tissue. Electroporation is suggested as the mechanism for enhanced diffusion. Mass transfer enhancement appears to be significant when the product initially possesses an intact cell structure. There appears to be a threshold potential above which significant increases in permeabilization occur. Except for DC, this potential is found to depend on frequency—the higher the frequency, the higher the threshold potential for permeabilization.

Modelling of dehydration-rehydration of orange slices in combined microwave/air drying

Abstract: The development of new citrus products, such as dry products for direct use or for rehydration, is interesting to promote their consumption. Combined microwaves (MW)–air (2 m/s, 60 °C) drying of orange slices has been studied in terms of process kinetics and of the rehydration capability as affected by the applied MW power (0, 0.17, 0.36, 0.69 and 0.88 W/g). Drying curves were modelled considering two periods, with different kinetic constants, related with the effective water diffusivity. These constants increased linearly with the applied MW power and, despite the low levels of MW power used, a sharp reduction in drying time of orange slices was obtained. Rehydration behaviour of orange slices was modelled through Peleg's and Weibull's equations. No differences in rehydrating behaviour were observed as a function of the applied MW power. So, the highest level, which was limited to avoid sample browning, will be recommended to reduce the drying time.

Modelling heat transfer in high pressure food processing: a review

Abstract: The most claimed advantage of high-pressure food processing as compared to thermal processing is that pressure acts instantaneously and uniformly through a mass of food independently of its size, shape or composition. Nevertheless, thermal gradients are established in the products after compression and cause inhomogeneities in the pursued pressure effect. Modelling heat transfer in high-pressure food processes can be a useful tool to homogenise and optimise these treatments. The main difficulty is the lack of appropriate thermophysical properties of the processed materials under pressure. When modelling high-pressure processes at subzero temperatures, pressure/temperature phase transition data and latent heat are also needed. Those for water are known, but there is a total lack for those corresponding to components relevant to foods. Moreover, the precise mechanisms that rule high-pressure shift freezing and induced thawing are not yet clear and so it hinders modellisation. This review collects the difficulties found and the advances made up to date in modelling heat transfer in high-pressure processes, including those performed at subzero temperatures.

Quality improvement and extension of shelf life by 1-methylcyclopropene in plum as affected by ripening stage at harvest

Abstract: Plum (Prunus domestica L. cv. ‘President’) fruits were harvested at two pre-climacteric stages of ripeness (stage 1 and stage 2), and then treated with 1-methylcyclopropene (1-MCP) at two doses (0.3 and 0.5 μl l−1) followed by 1, 2, 3, 4 and 5 weeks of cold storage and their respective 7 days of shelf life at 20 °C. Both 1-MCP doses were effective in terms of ethylene inhibition during shelf life after cold storage, for both ripening stages. Similarly, lower weight losses, delayed colour changes, reduced softening rate and diminished ripening index were found in 1-MCP treated plums than in controls at both stages of ripeness. Hence, during cold storage and shelf life, the efficacy of 1-MCP on ethylene production, weight loss, pulp firmness and ripening index was dose-dependent, while for colour and respiration rate the dose-dependence was only found during shelf life. The storability of 1-MCP treated plums could be extended up to 4 weeks of cold storage plus 7 days at 20 °C, and only up to 1 week of cold storage plus 7 days at 20 °C for controls. Then, 1-MCP is an effective tool for quality improvement and extension of shelf life in plums, and fruit might be harvested in stage 2 of ripening, at which the most desirable organoleptic attributes had been developed on tree.

Acrylamide in food: a model for mechanism of formation and its reduction

Abstract: Acrylamide and its analogues have been widely used since the last century for various chemical and environmental applications and can be formed by heating of biological material derived from plant tissues. This compound, identified previously as a potential industrial hazard, has now been found in many cooked foods. Reports of the presence of acrylamide in a range of fried and oven-cooked foods have caused worldwide concern because of its probable carcinogenicity in humans. The exact mechanism for the acrylamide formation in food is not well understood. The existing models to explain its formation have several limitations. This study was carried out to investigate the acrylamide formation in commonly consumed food stuff model and possible mechanisms of its reduction. Our system uses fried potato slices previously treated either with phenolic antioxidants from cranberry and oregano or coated with chickpea batter. We have shown that formation of acrylamide in fried potato chips is not an oxidative phenomenon and can be reduced by protective effects of chick pea proteins. Based on the results of our investigation we have proposed a non-oxidative model for acrylamide formation.

High pressure microfluidization treatment of heat denatured whey proteins for improved functionality

Abstract: Solutions (5% protein) of a whey protein concentrate (WPC) in fresh acid whey or in water, as well as the fresh whey alone, were adjusted to pH 5.8, 4.8 or 3.8, heat treated at 90 °C for 10 min and further exposed to high pressure (150 MPa) microfluidization treatment. The volumes of sediment after centrifugation were recorded as a measure of the degree of insolubility of the proteins. Microfluidization disrupted the heat-induced aggregates into non-sedimenting whey protein polymers so that in some cases, especially at pH 3.8, the products studied were almost completely resistant to sedimentation after the microfluidization treatments. Heat denatured/microfluidized whey proteins reaggregated upon subsequent heating, with the pH having a major impact on the amount of sediment produced. Microfluidization of aqueous WPC solutions heat-treated before spray- or freeze-drying substantially increased the solubility of the powders upon reconstitution. Heat-induced viscoelastic gels were produced from freeze-dried microfluidized samples processed at pH 3.8 and reconstituted to solutions containing 12% (w/w) protein.

Ohmic heating behaviour and electrical conductivity of two-phase food systems

Abstract: Ohmic heating behaviour and electrical conductivity (EC) of two-phase food systems were studied. Food systems were comprised of a liquid phase using 4% w/w starch solution with 0.5% w/w salt, and a solid phase containing carrot puree and cubes of different sizes (6 and 13 mm) in different concentrations (30 and 50% w/w). A set of experiments was carried out for a wide range of particle concentrations from 0 to 60% w/w. With respect to the particle location, experiments were conducted using 30% w/w cubes (6 mm) placed in parallel, in series and in well-mixed conditions with the liquid phase. Ohmic heating was applied to the food systems using a static cell (20-mm-long Teflon cylinder with 35 mm diameter and 25 mm wall thickness) at a constant voltage gradient of 12.5 V/cm. Electrical conductivity values were calculated as a function of particle size, concentration, location and temperature. It was observed that the heating time increased along with particle size and concentration. Overall values of EC ranged from 0.2 to 1.8 S/m, increasing with the process temperature as it ranged from 20–80 °C, and decreasing as particle size or concentration increased. With respect to the particle location within the ohmic cell, the thermal behaviour was different when the two phases were in parallel, in series or in mixed condition. However, there was no significant difference between overall values of EC when liquid and solid phases were separated as compared with the mixed condition.

Effects of combination treatments of nisin and high-intensity ultrasound with high pressure on the microbial inactivation in liquid whole egg

Abstract: The consecutive combinations of nisin with high hydrostatic pressure (nisin-HHP) and ultrasound with high hydrostatic pressure (US-HHP) were explored to achieve enhanced microbial inactivation in liquid whole egg processing. The HHP processing conditions were fixed to either 250 MPa for 886 s or 300 MPa for 200 s at the treatment temperature of 5 °C, which have been determined as the optimum HHP processing conditions considering egg protein coagulation and microbial inactivation kinetics. Between the two types of combinations, the nisin-HHP combination showed more promising results. The addition of nisin prior to pressure treatments significantly increased the lethal effects of HHP against Listeria seeligeri up to 5 log cycles. Because the individual effects of each nisin and HHP on the Listeria were almost negligible, the Listeria reductions are considered to be due to the synergistic action of nisin and HHP. However, the combination of nisin-HHP on E. coli showed exactly the same degree of inactivation by HHP alone, which supports protection mechanism of gram negative bacteria against the action of nisin. The US-HHP combination caused no reductions of Listeria and only a slightly increased inactivation of E. coli under the experimental conditions.

Non-contact bruise detection in apples by thermal imaging

Abstract: Thermal imaging is a non-destructive and non-contact infrared sensing technique. Such imaging creates a bit-map called a thermogram by detecting infrared radiation emitted from an object. Up to 100% of apple bruises were detected using thermal imaging during warming of the fruits by discriminating surface temperature between bruised and sound tissues. Apples were bruised by dropping them from 0.46 m onto a smooth concrete floor and then were held at 26 °C and 50% RH for 48 h. They were then thermally imaged using a ThermaCam™ PM390 (FLIR Systems, Inc., Portland, OR) during heating and cooling treatments. Thermal images of bruised tissue showed at least 1–2 °C difference from sound tissue within 30–180 s. The temperature differences between bruised and sound tissues were possibly due to the differences in thermal diffusivity. Under steady-state temperature, thermal imaging did not detect bruises, indicating that the temperature differences were not due to emissivity differences. The technique could provide a basis for automatic bruise sorting, and possibly a better understanding of bruised tissue.

Impact of high pressure assisted thawing on the quality of fillets from various fish species

Abstract: A comparison between the influence of pressure assisted thawing at 200 MPa and that of conventional thawing in 15 8C water at ambient pressure on the quality of thawed fish fillets has been carried out. Data showed that pressure assisted thawed and water thawed fillets exhibit visual differences. Organoleptic characteristics of the high pressure treated fillets were better compared to the conventional water thawed samples before cooking. Further differences were observed, in the total viable count of micro- organisms, pH value, water binding ability, instrumentally evaluated texture parameters and in thermoanalytical behaviour. Also, the effects of the selected treatments differed according to the fish species. Consequently, the specific properties of samples must be taken into consideration when designing pressure supported processes. 2003 Elsevier Science Ireland Ltd. All rights reserved. Industrial relevance: This paper is of high industrial relevance as it deals with an approach to solve the commercially important problem of thawing frozen fish. The use of high hydrostatic pressure enables the freezing and melting point to be controlled. The melting point of pure water can decrease to a temperature of y22 8C at a pressue of 209 MPa. Thus, a higher absolute temperature difference between the product and the surrounding medium can be achieved at moderate temperature levles. The necessary heat of fusion decreases likewise to a minimum at 209 MPa as compared to atmospheric pressure. Together these two effects result in an acceleration of the thawing process. A further target of the application of high pressure assisted thawing in the processing of fish is a reduction of the amount of tape water currently used as thawing medium.

Relative stabilities of microalgal carotenoids in microalgal extracts, biomass and fish feed: effect of storage conditions

Abstract: Carotenoids, whose functional importance has become the object of much attention in the last years, are a source of vitamin A and food colouring agents for both animals and/or humans. As consumer demand for natural carotenoids increases, there is a natural barrier to their utilisation insofar as their low stability to oxidative environments is concerned. The aim of this work was to test stability of carotenoids present in microalgal biomass, such as Chlorella vulgaris (Cv) and Haematococcus pluvialis (Hp), already proven to be efficient colouring agents and of their acetone extracts, both as such and in formulated feeds, under different storage conditions, namely at room temperature under light exposure, at room temperature in the dark, frozen at −18 °C, with added antioxidant (0.01% ascorbic acid at room temperature) and stored under vacuum or nitrogen atmosphere. The best storage conditions for microalgal dry biomass carotenoids were under vacuum in both microalgae, when retention totaled 80 and 90%, respectively, for Cv and Hp, even after 1.5 years. Carotenoid extract stabilities were found to be much shorter, and loss of carotenoid pigments was almost total after 15 and 30 days, respectively, for Cv and Hp. In formulated diets, carotenogenic biomass revealed stability during the maximum storage period of six months. As a conclusion, both microalgal dry biomasses may constitute natural, encapsulated and relatively concentrated forms of edible carotenoids, which exhibit good preservation without any special storage conditions, both as such or in finished fish feed.

Comparing predicting models for the Escherichia coli inactivation by pulsed electric fields

Abstract: Inactivation of Escherichia coli by pulsed electric field treatments (PEF) between 15 and 28 kV/cm in citrate–phosphate McIlvaine buffer (pH 7, 2 mS/cm) was studied. At all electric field strengths investigated the shape of the survival curves was concave upwards. A two-term exponential model for mixed cell populations, a model based on a Weibull distribution of resistances within the bacterial population, a sigmoidal equation also justified by the existence of a resistance distribution, and a purely empirical equation were used to fit the observed survival curves. The three last models were simpler than the first one and allowed to develop secondary models to estimate the influence of the electric field strength on the inactivation of E. coli. A validation study showed that the performance of models derived from the Weibull distribution and the empirical equation were better than the derived from the sigmoidal equation.

Comparative evaluation of the effects of pulsed electric field and freezing on cell membrane permeabilisation and mass transfer during dehydration of red bell peppers

Abstract: The extent of cell membrane permeabilisation due to high intensity electric field pulses (HELP) varying number of pulses (1–50) using electric field of 2 kV/cm, 400 μs pulse duration and freezing on mass transfer and vitamin C content during osmotic (50° Brix sucrose at 40 °C) and convective air (60 °C, 1 m/s for 5 h) dehydration of red bell peppers was studied. Total pore area due to HELP increased with number of pulses while freezing resulted in total pore area of almost 6 times as greater as the highest value from the HELP process. Higher water loss was observed for all HELP treated than for prefrozen samples while slow freezing provided samples with the highest solids uptake. The correlation coefficient (R2) of linear regression between water loss and solids gain estimated from either total solids or soluble solids measurement ranged from 0.954 to 0.998 suggesting the possibility of using the soluble solids method in evaluating mass transfer kinetics during osmotic dehydration process. Drying rate during convective air-drying was more enhanced by HELP than by freezing. Electrical conductivity of the osmotic solution increased with the degree of permeabilisation to a given medium value after which no further increase in the release of the intracellular ions was observed. Minimal vitamin C depletion was observed immediately after HELP treatment. The order of magnitude of vitamin C retention was untreated>frozen>HELP pretreated samples with 1 pulse>5 pulses>50 pulses>10 pulses>20 pulses after osmotic dehydration. The reduction in vitamin C content of HELP treated samples after convective drying ranged from approximately 11 to 24% while freezing resulted in approximately 24% decrease compared to the untreated samples.

Inactivation kinetics of polygalacturonase in tomato juice

Abstract: a ¸ ´´ ˜ ´ Abstract The inactivation kinetics of polygalacturonase (PG) in tomato juice was studied during thermal and high-pressureythermal processing. In the temperature range of 55-70 8C the thermal inactivation of polygalacturonase in tomato juice followed a fractional conversion model, with a thermostable fraction of approximately 14%. Under conditions of combined high-pressurey thermal processing, 200-550 MPay5-50 8C, PG inactivation presented first order kinetics. A mathematical model to describe the inactivation rate constant as a function of pressure and temperature was formulated. Industrial relevance: Polygalacturonase is responsible for the decrease of viscosity in tomato-based products. However, little research on thermal and high pressure ythermal inactivation kinetics of tomato Polygalacturonase has been reported. This research clearly shows that it is possible to selectively inactivate PG by high pressureythermal processing without applying high temperatures. This leads to tomato-based products with improved functional properties while other quality attributes (color, flavor, nutritional value ) are maintained. 2002 Elsevier Science Ltd. All rights reserved.

Fragmentation of chitosan by microfluidization process

Abstract: Fragmentation of chitosan in 0.1 M acetic acid (HAc) by microfluidization was investigated. The degree of fragmentation was followed by viscometry and size exclusion chromatography. The chemical structure of chitosan and its fragments was examined by elemental analysis and 1H NMR spectroscopy. Fragmentation of chitosan was affected by pressure or intensity of turbulence, exposure time, and hydrodynamic parameters such as molecular weight and polymer concentration in solution; but temperature had only a negligible effect. Chain scission increased bi-linearly with pressure, increased with molecular weight of chitosan but decreased with its concentration. Continuous microfluidization appeared to be more effective in fragmentation than volume pass mode. Molecular weight distribution of fragments was narrower than that of the original polymer indicating that large macromolecules were preferentially fragmented. Degree of acetylation of fragments increased when 0.1 M HAc was used as solvent for chitosan but not in 0.04 M HCl. The fragmentation of chitosan by microfluidization process was described by a parametric model relating chain scission to mechanical action and hydrodynamic parameters of the polymer. It was concluded that microfluidization can be a useful method for moderate fragmentation of chitosan.

Influence of high pressure on conformational changes of soybean glycinin

Abstract: Influence of high pressure on conformational changes of soybean glycinin was studied by means of sulphydryl groups detection, spectrofluorimetry, ultraviolet difference spectra, circular dichroism, differential scanning calorimetry and electrophoresis. The results indicated that glycinin were dissociated into subunits and the conformation of these subunits had been changed after high pressure processing. More sulphydryl groups as well as hydrophobic regions and amino acid residues which had ultraviolet absorbance had been found significantly after high pressure processing (≥300 MPa). DSC analysis results demonstrated that glycinin had been denatured completely after processed at 400 MPa for 10 min. The CD analysis indicated that some of the ordered structures of α-helix and β-structure were destroyed and converted to random coil after processed at 500 MPa for 10 min.

Inactivation of Bacillus subtilis spores by supercritical CO2 treatment

Abstract: Bacillus subtilis spores were suspended in saline solution (107 cfu/ml) and treated by both conventional heating and CO2 batch treatment at an operating pressure in the range of 70–150 bar under identical temperature conditions. Temperatures tested were in the range of 36–75 °C. Survival curves indicated significantly higher lethality when spores were treated with supercritical CO2 (SC-CO2) rather than with heating alone. These results appear particularly evident at 60 °C, a temperature at which conventional heating gave no spore-inactivation after a treating time as long as 24 h, whereas a 6 h SC-CO2 treatment led to complete sterilization. At 75 °C spores were partially killed with conventional heating but a treatment of 2 with SC-CO2 hours assured total inactivation. It is concluded that spore-inactivation during SC-CO2 treatment was only in part due to thermal effect (at the higher temperature of 75 °C) and there was a significant additional effect caused by CO2 penetration inside the latent bacteria forms.

Impact of air bubbles in a dielectric liquid when subjected to high field strengths

Abstract: The dielectric breakdown of gas bubbles entrapped in liquid food flowing through the cavity of a pulsed electric field treatment chamber has been a limiting factor in this non-thermal food preservation technology. Prediction of electric field enhancement due to gas bubbles is an important tool in the design, modification, and optimization of the treatment chamber's electrode geometry and pressurization. Simulation of the electrostatic characteristics of a coaxial treatment chamber with specified voltage of 25 kV, filled with dielectric material with conductivity of 0.6 S/m containing gas bubbles, evidenced a significant perturbation in the electric field. The magnitude of electric fields generated inside the bubbles was almost two times higher than in the homogeneous food. Without pressurization (atmospheric conditions), the dielectric breakdown strength of the gas-filled bubbles was exceeded, thus indicating the risk of arcing. A system pressurization of approximately 8 atm could be sufficient to limit arcing when small gas bubbles (∼1 mm) are present. The presence of gas bubbles caused the field magnitude to decrease significantly near the boundary of the bubble, thus threatening the uniformity of the PEF treatment across the chamber gap. This perturbation in the electric field was more significant when more than one bubble was present or when smaller gaps were used. The dielectric breakdown threshold at a given pressure is more likely to be exceeded by bigger bubbles (>1 mm) entrapped in a fluid processed in smaller treatment chamber gaps (3 mm), than by smaller bubbles (

Process for the recovery of a carotene-rich functional food ingredient from carrot pomace by enzymatic liquefaction

Abstract: A novel process for the recovery of a carrot pomace hydrolyzate rich in carotene was developed on pilot plant-scale. The process includes techniques of fine grinding, enzymatic hydrolysis, finishing, homogenization, and concentration. An extensive optimization of the enzymatic hydrolysis on a laboratory scale was performed before scaling up. An enzyme mixture composed of pectolytic and cellulolytic activities at a 1:1 ratio achieved the best degradation, and with a dosage of 1500 ppm at 50 °C and pH 4, the hydrolysis time was reduced to 1 h on pilot plant-scale. Total carotene content (α- and β-carotene) of the concentrated hydrolyzate (3.8 °Bx) was 64 mg per kg.

High pressure-induced changes in the creaming properties of bovine milk

Abstract: Creaming of raw whole bovine milk at refrigeration temperatures is generally regarded as an undesirable phenomenon; traditionally, creaming is prevented by homogenising the milk. The effects of high pressure (HP) processing on the creaming of raw whole bovine milk were examined in this study. HP treatment at pressures ≤250 MPa increased the rate and level of creaming, whereas treatment at ≥400 MPa reduced both of these parameters. On treatment at 200 or 600 MPa, creaming increased or decreased, respectively, with increasing treatment time. At 400 MPa, HP-induced changes in the rate and level of creaming were strongly treatment time-dependent. Treatment at 100–600 MPa for 0–60 min had little effect on milk fat globule size, whereas the viscosity of skimmed milk increased with increasing pressure and treatment time. The amount of milk protein associated with the milk fat globules was increased by HP treatment, the extent of the increase being maximal at 200 MPa. Although increased viscosity and the level of protein associated with the fat globules may partially explain the reduced rate and level of creaming, HP-induced aggregation and denaturation of agglutinins and lipoproteins are likely to have significant effects on HP-induced changes in the creaming characteristics of milk.

Burlat cherry quality after long range transport: optimisation of packaging conditions

Abstract: The purpose of this work was to determine the shelf life of Burlat cherries packaged in modified atmospheres during transportation and commercialisation. Cherries were harvested at commercial maturity and packaged in trays covered with polypropylene films with different permeabilities. All cherries were transported in a refrigerated truck from Zaragoza (Spain) to Milan (Italy) during a transport time of 5 days. After transportation, cherries were submitted to a commercialisation period. Our results show that modified atmosphere packaging using polypropylene films of intermediate permeability (238 ml O2 m−2 h−1 atm−1 or 423 ml O2 m−2 h−1 atm−1) extends postharvest cherry shelf life up to 15–20 days at 5 °C. Under these conditions acidity levels remain higher, anthocyanin synthesis is reduced, lower level of oxidative enzymes are detected, and texture and sensorial quality improve. Moreover, films of intermediate permeability allow a temporal breakage of the cold chain without any reduction in sensorial quality of the cherries.

Compositional characteristics and sensory quality of biscuits, prawn crackers and fried chips produced from beadfruit

Abstract: Breadfruit was processed into three unconventional food forms, namely into biscuits, prawn crackers and chips. The novel snack food items comprised of four biscuit samples made from wheat flour substituted with 33, 50, 67 and 100% breadfruit flour, one sample of prawn cracker made from breadfruit starch and one sample of fried breadfruit chips. These food items were subjected to proximate analyses and also comparative sensory evaluation alongside their respective commercial equivalents produced from the traditional or conventional foodstuffs. The panel of 24 people evaluated each category of sample for crispness, flavour, colour and overall preference on a 9-point hedonic scale. The proximate analyses showed that all the experimental products could contribute appreciable amounts of principal nutrients to the daily nutrient requirements of would-be consumers. Although there were statistically significant preferences ( P ≤0.05) between the test products and their commercial equivalents with respect to some quality attributes, all the experimental products except the biscuit from the 100% breadfruit flour were adjudged to be acceptable in terms of overall quality. The data presented in this study have demonstrated the potential for the industrial exploitation of breadfruit through processing into snack food items suitable for production in fast food service systems.

Firmness of pressure-induced casein and whey protein gels modulated by holding time and rate of pressure release

Abstract: The main protein fractions of milk, casein and whey protein, may react differently to processing due to their amino acid sequence and conformation and their ability to build up intermolecular covalent and non-covalent bonds. Gels made from solutions of micellar casein and whey protein isolate were induced by applying ultra-high pressure (600 MPa/30 °C). The pressure built up was held constant at 200 MPa min −1 , while the holding time of 0.15 and 30 min was varied as well as the pressure release rate (20, 200, 600 MPa min −1 ). The firmness of the pressure-induced whey protein gel was essentially influenced by the degree of whey protein denaturation and determined by the amount of disulfide bonds stabilizing the gel microstructure. In contrast, the firmness of pressure-induced casein-based gels was mainly influenced by pressure release rate. A slow pressure release produced a rough and weak gel. A high release rate, however, caused a homogeneous microstructure to be formed that created a high level of firmness.