Volume and density of whole soybean products during hot-air thermal treatment in fluidised bed

Soybeans contribute to healthy nutrition because of the high proportion and quality of proteins. Its oil content is considerably lower than in peanuts, restricting energy intake. To produce a whole soybean snack, four type of samples were processed by first increasing the water content and then reducing it by hot-air fluidisation: moistened-dried at 60 °C (MD), soaked-dried at 60 °C (SD), soaked and dried-toasted at 140 °C (SDT) and soaked-cooked and dried-toasted at 140 °C (SCDT). A semi-theoretical model was proposed to describe volume and density as a function of moisture during fluidisation. An equilibrium shrinkage coefficient a was determined. Volume expansion achieved by increasing the moisture content was not totally lost during fluidisation, allowing for lighter products, whose density decreased with the reduction in moisture. As the overall treatment was more severe (SCDT > SDT > SD > MD), shrinkage coefficients increased, up to 0.75. The SCDT sample became crispy and glassy after cooling.     

Purification and characterization of polyphenol oxidase from Ferula sp.

Polyphenol oxidase (PPO) of several Ferula sp. was extracted and purified through (NH₄)₂SO₄ precipitation, dialysis, and gel filtration chromatography. Leaf and stem extracts were used for the determination of enzyme properties. Optimum conditions, for pH, temperature, and ionic strength were determined. The best substrates of PPO were catechol for leaf and (−) epicatechin for stem samples. Optimum pH and temperature were determined. K_M and V_max values were 2.34 × 10⁻³ M and 8541 EU/ml for catechol, and 2.89 × 10⁻³ M and 5308 EU/ml for (−) epicatechin. The most effective inhibitor was sodium diethyl dithiocarbamate for leaf samples and sodium metabisulphite for stem samples. Both inhibitors indicated competitive reactions. PPO showed irreversible denaturation after 40 min at 60 °C.     

The effect of sulphuric acid activation on the crystallinity,surface area,porosity, surface acidity,and bleaching power of a bentonite

The Hanç?l? (Keskin, Ankara, Turkey) bentonite was activated with H₂SO₄ by dry method at 97 °C for 6 h to obtain optimum parameters for imparting a maximum bleaching power towards soybean oil. The H₂SO₄ content in dry bentonite-acid mixture was changed between 0% and 70%. The natural and activated samples were examined by X-ray diffraction (XRD), N₂ adsorption–desorption, and n-butylamine adsorption (from the solution in cyclohexane). The specific surface area (S), specific micro–mesopore volume (V), mesopore size distribution (PSD), and surface acidity (n_m) of the samples were determined. The bleaching power (BP) of each sample for alkali-refined soybean oil was determined. The S, V, n_m, and BP increase after activation at various acid contents up to 40% H₂SO₄ without any considerable change in crystal structure of the smectite. The BP is controlled more by the PSD rather than other adsorptive properties of the bleaching earth. The optimum parameters for activation to obtain maximum bleaching power, are H₂SO₄% = 50–60, S = 250–230 m² g⁻¹, V = 0.46–0.47 cm³ g⁻¹, n_m = 9.0 × 10⁻⁴–8.4 × 10⁻⁴ mol g⁻¹ and PSD mainly distributed between 1.4 and 6.0 nm.     

Kinetics and modeling of whole longan with combined infrared and hot air

The aim of this research was to evaluate the effects of operating variables on the drying behavior of whole longan undergoing a combined infrared and hot air drying process, to determine its kinetic parameters, and to develop drying kinetic models. The single-layer drying experiments were carried out at infrared powers of 300, 500 and 700 W, drying air temperatures of 40, 60 and 80 °C, and air velocities of 0.5, 1.0 and 1.5 m/s. The samples were dried until attaining a final moisture content of 0.2 kg water/kg dry solid. The results show that the drying had a short constant rate period followed by a falling rate period in all cases. The drying rate and product temperature were significantly influenced by infrared power, temperature and velocity of ambient air. In the constant rate period, the mass transfer coefficient varied from 3.646 × 10⁻³ to 1.914 × 10⁻² m/s. It increased with increasing infrared power, but decreased as air velocity and air temperature increased. In the falling rate period, theoretical and semi-empirical drying kinetic equations were used to describe the drying kinetics of the product. It was found that the overall effective diffusion coefficient and drying constant varied from 7.012 × 10⁻¹¹ to 6.681 × 10⁻¹⁰ m²/s and 0.026 to 0.234 h⁻¹, respectively. Both parameters increased with increasing infrared power and air temperature, but decreased with increasing air velocity. Combined regression equations developed to predict the drying kinetic parameters (h_D, D_eff and k) for all three models gave a fairly good fit.     

Effect of chemical and physical pretreatments on the convective drying of cape gooseberry fruits (Physalis peruviana)

Drying of cape gooseberry fruits is a slow process because of the low permeability to moisture of the fruit’s waxy skin. In this work, the effect of chemical pretreatments (sunflower oil/K₂CO₃ or olive oil/K₂CO₃ at 28 °C, and NaOH/olive oil at 96 °C) and physical pretreatments (blanching) to break down the waxy surface and accelerate moisture diffusion during drying, was assessed. Drying was carried out at 60 °C and 2 m/s air velocity for 10 h. The lowest moisture content (0.27 kg water/kg db), the highest vitamin C content (0.36 mg/g), and the greatest rehydration capacity (1.89) were obtained in fruits pretreated with olive oil (9.48%) and K₂CO₃ (4.74%). However, the greatest changes in color (ΔE^* = 15.05) and chroma (ΔC^* = 9.03) were also associated to fruits pretreated with olive oil and K₂CO₃. The effective diffusivity of water during drying was 7.37 × 10⁻¹¹ m²/s in pretreated samples compared with 6.61×10⁻¹¹ m²/s for untreated samples.     

Weibull distribution for modeling air drying of coroba slices

Application of Weibull distribution model was investigated for describing the moisture content of coroba slices during air drying. One set of experiments was performed following a full factorial design at three levels for air temperature (71, 82 and 93 °C) and velocity (0.82, 1.00 and 1.18 m/s). The set was designed to assess the adequacy of the Weibull model to describe water losses. The high regression coefficients (R² > 0.99) and low reduced chi-square indicated the acceptability of Weibull model for predicting moisture content. Values of scale parameter ranged from 41.77 to 71.52 (min) and values of shape parameter ranged from 1.06 to 1.21. Temperature sensitivity of scale parameter increased with increasing air velocity from 0.82 m/s (E_a = 210.45 J/mol) to 1.00 m/s (E_a = 214.93 J/mol) and then decreased with increasing velocity to 1.18 m/s (E_a = 139.03 J/mol). The normalized Weibull model was investigated for determining the effective diffusion coefficient (D_e). The D_e values ranged approximately from 2.51 × 10⁻¹² m²/s to 4.27 × 10⁻¹² m²/s.     

Kinetic characterisation and thermal inactivation study of polyphenol oxidase and peroxidase from table grape (Crimson Seedless)

Polyphenol oxidase (PPO) and peroxidase (POD) were extracted from a table grape (Crimson Seedless) using Triton X-114 and characterized using spectrophotometric methods. Both PPO and POD were activated by acid shock. However, in the presence of the anionic detergent sodium dodecil sulphate (SDS), PPO was activated whereas POD was inactivated. The enzymes were kinetically characterized and both followed Michaelis–Menten kinetics, although with different values of their kinetic parameters. The V_m/K_m ratio showed that Crimson Seedless grape PPO presents a similar affinity for 4-tert-butyl-catechol (TBC) whether activated by acid shock (0.018 min⁻¹) or SDS (0.023 min⁻¹). With regards to POD, the K_m and V_m values for 2,2′-azinobis(3-ethylbenzothiazolinesulphonic acid) (ABTS) were 0.79 mM and 1.20 μM/min, respectively. In the case of H₂O₂, the K_m and V_m value were 0.4 mM and 0.93 μM/min, respectively. PPO and POD showed similar thermostability, losing >90% of relative activity after only 5 min of incubation at 78 °C and 75 °C, respectively. In addition, PPO´s activation energy was similar to that obtained for POD (295.5 kJ/mol and 271.9 kJ/mol, respectively).     

Emulsions stabilized by heat-treated collagen fibers

The emulsifying properties of collagen fiber were modified by heat treatment at temperatures ranging from 50 to 85 °C for 20 or 60 min. In addition to heat treatment, the influence of pH (3.5 and 9.2) and the emulsifying process (rotor-stator device and high-pressure homogenizer) were evaluated on oil-in-water emulsions stabilized by collagen fiber through visual analysis (stability), microstructure and rheological measurements. Emulsions homogenized using solely the rotor-stator device showed phase separation and a larger mean droplet size (d₃₂), except for the emulsion composed by non-heated collagen fiber. The alkaline emulsions showed lower kinetic stability, since collagen fibers have a lower net charge (zeta potential) at higher pH values, decreasing the electrostatic stability process. Heat treatment slightly decreased the protein charge and significantly reduced the insoluble protein content, suggesting a decrease in the emulsifying properties of the collagen fiber. The use of high-pressure homogenization (20-100 MPa) made it possible to produce acid emulsions with a reduced droplet size and distribution. At 20 MPa, the emulsions showed a higher d₃₂ value (between 3.17 and 1.18 μm), while at 60 and 100 MPa the emulsions presented lower d₃₂ values (between 0.74 and 0.94 μm) without any significant variation between the different heat-treated collagen fibers, but showing a noticeable decrease in emulsion viscosity and elasticity with increases in the homogenization pressure and heat treatment.     

Identification and quantification of fungi and mycotoxins from Pu-erh tea

Pu-erh tea originates from the province of Yunnan in south-western China. As this tea is produced by so called Aspergillus post-fermentation the question arises which molds and mycotoxins may be found in this tea. In total 36 samples of Pu-erh tea were investigated for their content of filamentous fungi and the mycotoxins aflatoxins B₁, B₂, G₁, and G₂, fumonisins B₁, B₂, and B₃, and ochratoxin A. Fungi were isolated from all samples in a concentration of 1.0 × 10¹ to 2.6 × 10⁶ colony forming units (cfu)/g tea, all together 19 fungal genera and 31 species were identified. The most prevalent species were Aspergillus acidus and Aspergillus fumigatus, followed by Zygomycetes and Penicillium species. Aflatoxins and fumonisins were not found in the samples investigated, ochratoxin A was detected in 4 of 36 teas (11.1%).     

Extraction, thermal stability and kinetic behavior of pectinmethylesterase from hawthorn (Crataegus pubescens) fruit

Pectinmethylesterase (PME) extracted from hawthorn (Crataegus pubescens) fruit was evaluated for its thermal stability and kinetic behavior. The enzyme extraction process was established after studying different NaCl concentrations (0.5-3.0 moles/L). A maximum PME extraction of 51.61 units/mg protein was obtained using 2 moles/L NaCl. Kinetic parameters (K_m and V_max) were determined using a commercial citrus pectin and C. pubescens pectin as substrates. The effects of NaCl concentration, pH and temperature on PME activity were investigated. PME showed higher affinity for C. pubescens pectin (K_m and V_max of 2.84 mg/mL protein, and 64.10 units/mg protein, respectively) than for citrus pectin. C. pubescens PME extract showed maximum activity at 0.4 moles/L NaCl, pH 7.5, and 55 °C. The E_a and Q₁₀ for thermal activation were 36.27 kJ/mol and 2.01 (20-30 °C), respectively. About 50% of the activity still remained after heating for 25 min at 60 °C, and it was completely inactivated by incubation at 80 °C for 10 min. The Q₁₀ and E_a values for thermal inactivation reaction were 20.06 (70-80 °C) and 146.16 kJ/mol, respectively. These results provide useful information about the factors that affect the activity of C. pubescens PME, and might be used as a starting point for texture control during post-harvest handling and processing of this fruit.     

Characterisation of lipoxygenase from pea seeds (Pisum sativum var. Telephone L.)

Lipoxygenase (LOX) from pea seeds (Pisum sativum var. Telephone L.) was extracted and studied of biochemical properties. The molecular mass of purified lipoxygenase was 93 kDa. The effects of substrate specificity, pH, and sensibility to various inhibitors: caffeic acid, ferulic acid, benzoic acid, catechin, quercetin and kaempferol of LOX were investigated. Lipoxygenase showed the highest activity toward linoleic acid and the lowest toward oleic acid as substrates. Kinetic studies indicated that V_max of the LOX activity was 151.5 U/min and corresponding K_m value of 0.44 × 10⁻³ M. Optimum pH of lipoxygenase was reported at 5.5. Caffeic acid was the most effective inhibitor and kaempferol was the least effective.     

High-pressure destruction kinetics of Clostridium sporogenes ATCC 11437 spores in milk at elevated quasi-isothermal conditions

The high-pressure sterilization establishment requires data on isobaric and isothermal destruction kinetics of baro-resistant pathogenic and spoilage bacterial spores. In this study, Clostridium sporogenes 11437 spores (10⁷ CFU/ml) inoculated in milk were subjected to different pressure, temperature and time (P, T, t) combination treatments (700–900 MPa; 80–100 °C; 0–32 min). An insulated chamber was used to enclose the test samples during the treatment for maintaining isobaric and quasi-isothermal processing conditions. Decimal reduction times (D values) and pressure and temperature sensitivity parameters, Z_T (pressure constant) and Z_P (temperature constant) were evaluated using a 3 × 3 full factorial experimental design. HP treatments generally demonstrated a minor pressure pulse effect (PE) (no holding time) and the pressure hold time effect was well described by the first order model (R² > 0.90). Higher pressures and higher temperatures resulted in a higher destruction rate and a higher microbial count reduction. At 900 MPa, the temperature corrected D values were 9.1, 3.8, 0.73 min at 80, 90, 100 °C, respectively. The thermal treatment at 0.1 MPa resulted in D values 833, 65.8, 26.3, 6.0 min at 80, 90, 95, 100 °C respectively. By comparison, HP processing resulted in a strong enhancement of spore destruction at all temperatures. Temperature corrected Z_T values were 16.5, 16.9, 18.2 °C at 700, 800, 900 MPa, respectively, which were higher than the thermal z value 9.6 °C. Hence, the spores had lower temperature sensitivity at elevated pressures. Similarly, corrected Z_P values were 714, 588, 1250 MPa at 80, 90, 100 °C, respectively, which illustrated lower pressure sensitivity at higher temperatures. By general comparison, it was concluded that within the range operating conditions employed, the spores were relatively more sensitive to temperature than to pressure.     

Adsorption of dark compounds with bentonites in apple juice

The adsorption equilibrium of dark-coloured compounds from apple juice has been investigated as a function of several variables including activation conditions of bentonite (heat and acid treatments), clay concentrations (2×10⁻³-8×10⁻³ kg clay/dm³ apple juice) and temperature (range of 296-336 K). The adsorption efficiency with acid-activated bentonite was greater than that with heat-activated and native bentonite, depending on surface properties; specific surface areas were 95.31, 71.95 and 71.76 m²/g, respectively.Absorbance data at 420 nm were fitted reasonably well with the Langmuir and Freundlich isotherms. The parameters K, Q₀, K_fr and n were determined for different temperatures. Thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) change of adsorption were determined as about −3.125, 9.43 and 0.039 kJ mol⁻¹ K⁻¹, respectively, for acid-activated bentonite. These parameters were also determined for native and heat-activated bentonites. It was shown that the adsorption process was endothermic, spontaneous and controlled by physical mechanism. The adsorption and desorption rate constants (k_a and k_d) were obtained separately by applying a geometric approach to the first-order Langmuir model. k_a varied from 5.717×10⁻⁴ to 20.667×10⁻³ s⁻¹ and k_d from 1.425×10⁻⁴ to 7.473×10⁻³ s⁻¹. The results showed that acid-activated bentonite is more suitable for the adsorption of dark compounds from apple juice.     

Evaluation of the performance of osmotic dehydration sheets on freshness parameters in cold-stored beef biceps femoris muscle

This study aimed to evaluate the effects of osmotic dehydration sheet (ODS) packaging on the quality parameters of beef biceps femoris muscle samples stored at 4 °C for 0, 1, 3 and 7 days. Quality indices such as Hunter color values (L^∗, a^∗ and b^∗, the percentage of metmyoglobin (Met-Mb%), K value (freshness index), and the contents of adenosine triphosphate (ATP)-related compounds (ARCs), thiobarbituric acid reactive substances (TBA-RS) and volatile basic nitrogen (VBN) were measured. ODS gave lower a^∗ and b^∗ values and lower Met-Mb% compared with control samples wrapped in polyvinylidene chloride film (PVDCF) (P < 0.01), but had no effect on L^∗ (P < 0.01). As a result, with higher levels of osmotic dehydration produced by the ODS, the percentage of weight loss and the total contents of ARCs and inosine monophosphate of the samples also increased (P < 0.05). The K values of ODS samples were also significantly lower than PVDCF-wrapped samples (P < 0.05). Low performance ODS wrapping reduced the TBA-RS values below those found with PVDCF and high performance ODS processing (P < 0.01). Moreover, the use of ODS had no effect on VBN values. Thus, although the bright red of beef samples changed to a dark purple color and the weights of samples decreased, the ODS approach has potential as a tool for decreasing the deterioration of other quality indices such as Met-Mb%, TBA-RS, ARCs, K values and the VBN content of cold-stored beef.     

Enzymic production of feruloyl xylo-oligosaccharides from corn cobs by a family 10 xylanase from Thermoascus aurantiacus

Feruloyl xylo-oligosaccharides (FeXOSs) were obtained from corn cobs (CCs) by treatment with a Thermoascus aurantiacus family 10-β-d-endoxylanase. CCs subjected to a sonication (ST-CC) or an autoclave treatment in order to enhance enzymic access and FeXOS production. Enzymic FeXOS production was increased by CCs thermal treatment up to 3.5 times. The kinetic parameters K_E and V_max, describing enzyme-dependent production rates of FeXOSs from CCs, were estimated at 130±20 nM and 290±10 nM h⁻¹, respectively. The reaction parameters affecting the FeXOS production, such as substrate concentration, enzyme loading and reaction time, have been investigated. The maximum FeXOS production was observed after 24 h incubation of 100 g L⁻¹ AT-CC with 570 nM xylanase. The obtained yield was 12 μmol of FeXOSs per gram of CC.     

Alcoholysis of salicornia oil using free and covalently bound lipase onto chitosan beads

Porcine pancreatic lipase was immobilized on chitosan by covalent binding and retention of its activity was examined. The activities of free and immobilized lipase were determined using olive oil as substrate. The free and immobilized enzymes showed pH 9 as optimum and retained 50% of activity after five cycles. When the substrate concentration was kept constant and enzyme concentration was varied, the K_m and V_max were observed to be 4.0 × 10⁻⁷ and 0.32, and 3.32 × 10⁻⁷ and 0.32, respectively, for free and covalently bound enzyme. This indicates that there is no possibility of conformational change during immobilization. Immobilized enzyme showed improved thermal and storage stability. Alcoholysis of salicornia oil, mediated by free and immobilized lipase, was carried out at 25 °C using methanol in hexane and acetone. Free and immobilized enzyme in hexane produced, respectively, 45% and 55% of fatty acid methyl ester after 12 h.     

Properties of polyphenol oxidase from Anamur banana (Musa cavendishii)

Polyphenol oxidase (PPO) was extracted from Anamur banana, grown in Turkey, and its characteristics were studied. The optimum temperature for banana PPO activity was found to be 30 °C. The pH-activity optimum was 7.0. From the thermal inactivation studies, in the range 60–75 °C, the half-life values of the enzyme ranged from 7.3 to 85.6 min. The activation energy (E_a) and Z values were calculated to be 155 kJ mol⁻¹ and 14.2 °C, respectively. K_m and V_max values were 8.5 mM and 0.754 OD₄₁₀ min⁻¹, respectively. Of the inhibitors tested, ascorbic acid and sodium metabisulphite were the most effective.     

Fat content increases the lethality of ultra-high-pressure homogenization on Listeria monocytogenes in milk

Listeria monocytogenes CCUG 15526 was inoculated at a concentration of approximately 7.0 log₁₀ cfu/mL in milk samples with 0.3, 3.6, 10, and 15% fat contents. Milk samples with 0.3 and 3.6% fat content were also inoculated with a lower load of approximately 3.0 log₁₀ cfu/mL. Inoculated milk samples were subjected to a single cycle of ultra-high-pressure homogenization (UHPH) treatment at 200, 300, and 400 MPa. Microbiological analyses were performed 2 h after the UHPH treatments and after 5, 8, and 15 d of storage at 4°C. Maximum lethality values were observed in samples treated at 400 MPa with 15 and 10% fat (7.95 and 7.46 log₁₀ cfu/mL), respectively. However, in skimmed and 3.6% fat milk samples, complete inactivation was not achieved and, during the subsequent 15 d of storage at 4°C, L. monocytogenes was able to recover and replicate until achieving initial counts. In milk samples with 10 and 15% fat, L. monocytogenes recovered to the level of initial counts only in the milk samples treated at 200 MPa but not in the milk samples treated at 300 and 400 MPa. When the load of L. monocytogenes was approximately 3.0 log₁₀ cfu/mL in milk samples with 0.3 and 3.6% fat, complete inactivation was not achieved and L. monocytogenes was able to recover and grow during the subsequent cold storage. Fat content increased the maximum temperature reached during UHPH treatment; this could have contributed to the lethal effect achieved, but the amount of fat of the milk had a stronger effect than the temperature on obtaining a higher death rate of L. monocytogenes.     

Distribution of zearalenone in malted barley fractions dependent on Fusarium graminearum growing conditions

Zearalenone (ZON) distribution was measured in main fractions of malted barley, dependent on incubation time (17, 26, 34 days), water activity (0.95 and 0.98) and temperature (20 °C and 30 °C). Malted samples were sterilised and inoculated with Fusarium graminearum. ZON levels were higher (p < 0.01) in bran and germ than flour under almost all growing conditions. Incubation at 30 °C resulted in generally lower ZON levels in germ and bran, regardless of a_w and incubation time. After 34 days, ZON levels in flour from samples that were incubated at the higher temperature rose significantly. At 20 °C ZON concentration showed a bell-shaped concentration profile with increasing incubation time in bran and germ, whilst ZON levels in flour increased at a_w 0.98 and dropped at the lower a_w. The results indicate the importance of storage conditions for ZON levels in commercially relevant grain fractions of malted barley and help predict existing mycotoxin levels or manipulate storage conditions to reduce ZON content.     

Molecular mass distribution of dextran in Brazilian sugar and insoluble deposits of cachaça

The dextran molecular mass distribution profile in 77 sugar samples from Brazil and twelve insoluble deposits (alcoholic flocks) samples from sugared cachaças (Brazilian sugar cane spirit) is described in terms of number-average molecular mass M_n, weight-average molecular mass M_w, Z-average molecular mass M_z, and polydispersity. The analyses were performed by size-exclusion chromatography, using a refractive index detector. In most of the sugar samples, it was possible to identify two major groups of dextrans with M_w averages of 5 × 10⁶ and 5 × 10⁴ Da. Based on the evaluated parameters, the dextran distribution profile is about the same in samples analyzed over five seasons, and, therefore, it is likely that the Brazilian product pattern will not change very much over the years. In insoluble deposits from sugared cachaças, dextrans with M_w values in the order of the 10⁵ Da were the most frequent ones, being present in 58% of the samples.