Prediction of the Glass Transition Temperature on Extruded Waxy Maize and Rice Starches in Presence of Glycerol

Polymer science approach has shown to be useful to understand the structural complexity of food systems. This work looks at the effect of glycerol (5%, 10%, and 20% (dry weight basis)) on the glass transition temperature (Tg) of a starchy matrix determined by DSC and its prediction using Ten-Brinke–Karasz equation. Waxy maize starch (WMS) and rice starch (RS) systems were prepared by thermomechanical extrusion. A decrease in Tg, from ∼170 to ∼25 °C, was detected for both starches (0% glycerol) when the moisture increased from 5% to 25% (wet weight basis (wb)). When glycerol was added, a further decrease in Tg was obtained. Tg was reduced from 120 to 60 °C and 45 °C for 10% and 20% glycerol, respectively, at a moisture content of 10% (wb). A direct comparison between starches with similar composition showed equal Tg (P > 0.05). The modeling for the control samples (0% glycerol) gave a ΔCp ∼ 0.4 Jg⁻¹ K⁻¹ for WMS and RS and ∼1.9 Jg⁻¹ K⁻¹ for water. These values can be explained by the well-known Tg dependence on degree of polymerization and molecular weight. When the glycerol concentration was increased, an increase was observed, ΔCp ∼ 0.6 Jg⁻¹ K^−1, for both starches and ∼2.8 Jg⁻¹ K⁻¹ for water. This behavior would indicate an overestimation in the plasticizing effect of glycerol due to the possible occurrence of polyol-rich fractions in the extruded samples.     

Spectroscopic and molecular docking studies of the interactions of sunset yellow and allura red with human serum albumin

Binding interactions of human serum albumin (HSA) with sunset yellow (SY) and allura red (AR), two food colorants, were investigated at the molecular level through fluorescence and UV absorption as well as molecular docking. The collective results of the study under the simulated physiological conditions proposed a static type of binding occurring between the two dyes and HSA. When compared with AR (293 K: Ksv = (4.21 ± 0.36) × 10⁴ L·mol⁻¹; K_b = (0.30 ± 0.23) × 10⁶ L·mol⁻¹), SY (293 K: Ksv = (6.80 ± 0.10) × 10⁴ L·mol⁻¹; K_b = (3.11 ± 2.01) × 10⁶ L·mol⁻¹) had stronger quenching ability and higher affinity for HSA due to less steric hindrance. It can be deduced that the energy transfer from HSA to the two dyes occurred with high probability based on the Förster resonance energy transfer theory (r < 7 nm, 0.5 R₀ < r < 2.0 R₀). The spectral analysis suggested that the formation of the dye-HSA complex resulted in the change in microenvironment around Tyr and Trp residues and in the secondary structure of the protein. According to molecular docking simulation, the two structural analogs almost bound to the same site of HSA, near Sudlow's Site I, but significant difference existed in the number and location of hydrogen bond (H-bond) formed between the dyes and HSA. From the molecular docking along with the thermodynamic parameters (AR: ΔH^o = −(58.79 ± 15.24) kJ·mol⁻¹, ΔS^o = −(115.1 ± 31.10) J·mol⁻¹·K⁻¹; SY: ΔH^o = −(52.24 ± 3.15) kJ·mol⁻¹, ΔS^o = −(50.07 ± 11.14) J·mol⁻¹·K⁻¹), it could be inferred that H-bond and van der Waals forces were the major binding forces involved in formation of the dye-HSA complexes.     

Kinetics of Crude Peroxidase Inactivation and Color Changes of Thermally Treated Seedless Guava (Psidium guajava L.)

Thermal treatment of seedless guava (Psidium guajava L.) cubes was carried out in the temperature range of 80–95 °C. The kinetics of peroxidase inactivation and color changes due to thermal treatments were determined. Peroxidase inactivation followed a first-order kinetic model, where the activation energy was 96.39 ± 4 kJ mol⁻¹. Color was quantified in terms of L, a, and b values in the Hunter system. The color changes during processing were described by a first-order kinetic model, except total color difference which followed a zero-order kinetic model. The temperature dependence of the degradation followed the Arrhenius relation. The activation energies (E _a) for L, a, b, and total color difference (ΔE) were 122.68 ± 3, 88.47 ± 5, 104.86 ± 5, and 112.65 ± 5 kJ mol⁻¹, respectively. The results of this work are a good tool to further optimize seedless guava thermal treatment conditions.     

Properties of <Emphasis Type="Italic">Aspergillus subolivaceus</Emphasis> free and immobilized dextranase

Aspergillus subolivaceus dextranase is immobilized on several carriers by entrapment and covalent binding with cross-linking. Dextranase immobilized on BSA with a cross-linking agent shows the highest activity and considerable immobilization yield (66.7%). The optimum pH of the immobilized enzyme is shifted to pH 6.0 as compared with the free enzyme (pH 5.5). The optimum temperature of the reaction is resulted at 60 °C for both free and immobilized enzyme. Thermal and pH stability are significantly improved by the immobilization process. The calculated K _m of the immobilized dextranase (14.24 mg mL⁻¹) is higher than that of the free dextranase (11.47 mg mL⁻¹), while V _max of the immobilized enzyme (2.80 U μg protein⁻¹) is lower than that of the free dextranase (11.75 U μg protein⁻¹). The immobilized enzyme was able to retain 76% of the initial catalytic activity after 5.0 cycles.     

Quenching of excited states of red-pigment zinc protoporphyrin IX by hemin and natural reductors in dry-cured hams

Zinc protoporphyrin IX (ZnPP), the major red pigment in hams dry-cured without nitrates/nitrites, is an efficient photosensitizer, which upon absorption of visible light forms short-lived excited singlet state (¹ZnPP*) and by intersystem crossing yields the very reactive triplet-excited state (³ZnPP*). Using nano-second laser flash photolysis and transient absorption spectroscopy NADH, ascorbic acid, hemin and dehydroascorbic acid were each found to be efficient quenchers of ³ZnPP*. The deactivation followed, in homogeneous dimethyl sulfoxide (DMSO) or DMSO:water (1:1) solutions, second-order kinetics. The rate constant for ascorbic acid and NADH for reductive quenching of ³ZnPP* was at 25 °C found to be 7.5 ± 0.1 × 10⁴ L mol⁻¹ s⁻¹ and 6.3 ± 0.1 × 10⁵ L mol⁻¹ s⁻¹, respectively. The polyphenols catechin and quercetin had no effect on ³ZnPP*. The quenching rate constant for oxidative deactivation of ³ZnPP* by dehydroascorbic acid and hemin was at 25 °C: 1.6 ± 0.1 × 10⁵ L mol⁻¹ s⁻¹ and 1.47 ± 0.1 × 10⁹ L mol⁻¹ s⁻¹, respectively. Oxidized glutathione did not act as an oxidative quencher for ³ZnPP*. After photoexcitation of ZnPP to ¹ZnPP*, fluorescence was only found to be quenched by the presence of hemin in a diffusion-controlled reaction. The efficient deactivation of ³ZnPP* and ¹ZnPP* by the metalloporphyrin (hemin) naturally present in meat may accordingly inherently protect meat proteins and lipids against ZnPP photosensitized oxidation.     

Benzyloxybenzaldehydethiosemicarbazone: Extractive Spectrophotometric Reagent for the Determination of Cu(II) in Food and Water Samples

Benzyloxybenzaldehydethiosemicarbazone (BBTSC) was prepared and developed a new method for the simple, highly selective, and extractive spectrophotometric determination of copper(II) with BBTSC at wavelength 370 nm. The metal ion formed a bluish green colored complex with BBTSC in acetate buffer of pH 5.0, which was easily extractable into n-butanol with 1:1(metal/ligand) composition. The method obeys Beer’s law in the range of 0.5–5.2 ppm. The molar absorptivity and Sandell’s sensitivity were found to be 1.5 × 10⁴ l mol⁻¹ cm⁻¹ and 0.00412 g cm⁻², respectively. The correlation coefficient of the Cu(II)–BBTSC complex was 0.998, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD; n = 10), which was 0.377% and its detection limit 0.0204 μg ml⁻¹. The interfering effect of various cations and anions were also studied. The proposed method was successfully applied to the determination of copper(II) in food and water samples. Comparing the results with those obtained using an atomic absorption spectrophotometer tested the validity of the method.     

Polycyclic aromatic hydrocarbons (PAHs) in traditional and industrial smoked beef and pork ham from Serbia

Smoked beef and pork ham samples were analysed during process of smoking (after packing and storing) for the presence of the 16 EU priority PAHs via Fast GC/HRMS method. This study showed that there are differences in PAH contents between final smoked beef ham samples from traditional smokehouse (TS) (3.9 μg kg⁻¹) and industrial smokehouse (IS), (1.9 μg kg⁻¹). Also there is a difference in PAH contents in final smoked pork ham samples (4.9 μg kg⁻¹, TS; 4.2 μg kg⁻¹, IS). In beef and pork ham samples from the same smokehouse different PAH contents were observed during smoking. The highest content of examined PAHs in all beef and pork ham samples during smoking showed benzo[c]fluorene (BcL) (beef ham: from 0.3 μg kg⁻¹ to 1.5 μg kg⁻¹; pork ham: from 0.2 μg kg⁻¹ to 2.1 μg kg⁻¹).The maximum level for benzo[a]pyrene (BaP) of 5 μg kg⁻¹ in smoked meat products was not exceeded in any samples. Correlation statistic analysis (P < 0.05) of obtained contents from samples both from TS and IS showed that BaP is a good marker both for 16 EU priority PAHs and 12 IARC probably and possibly carcinogenic PAHs (IS: R _BaP/Σ16PAHs = 0.95, R _BaP/Σ12PAHs = 0.96; TS: R _BaP/Σ16PAHs = 0.71, R _BaP/Σ12PAHs = 0.88).     

Mass Transfer Modelling During Osmotic Dehydration of Jumbo Squid (Dosidicus gigas): Influence of Temperature on Diffusion Coefficients and Kinetic Parameters

Mathematical modelling was used to study the effect of process temperature on moisture and salt mass transfer during osmotic dehydration (OD) of jumbo squid with 6% (w v ⁻¹) NaCl at 75, 85 and 95 °C. The diffusion coefficients for moisture and salt increased with temperature. Based on an Arrhenius-type equation, activation energy values of 62.45 kJ mol⁻¹ and 52.14 kJ mol⁻¹ for moisture and salt, respectively, were estimated. Simulations of mass transfer for both components were performed according to Newton, Henderson and Pabis, Page, Weibull and logarithmic mathematical expressions. The influence of drying temperature on the kinetic parameters was also studied. Based on statistical tests, the Weibull and logarithmic models were the most suitable to describe the mass transfer phenomena during OD of jumbo squid.     

A Rapid Spectrophotometric Method for Trace Determination of Zinc

A simple, sensitive, and highly selective method is proposed for the determination of zinc(II) using a bis-azo dye, 2,6-bis(1-hydroxy-2-naphthylazo)pyridine as spectrophotometric reagent. At pH 7.8, in 50% (v/v) ethanol–water medium, the complex is found to obey Beer’s law up to 1.3 mg/L with an optimum concentration range between 0.19 and 1.0 mg/L. Sandell’s sensitivity of the color reaction was calculated to be 0.0011 μg cm⁻² with molar absorptivity of 6.0 × 10⁴ L mol⁻¹ cm⁻¹ at 560 nm. The optimum conditions for the determination of Zn(II) with the reagent were ascertained. The complexation at different pH was studied in water–ethanol medium. The composition of the complex is 1:2. The action of some interfering ions was verified, and the developed method applied successfully for the estimation of zinc levels in food and milk samples, and the results were then compared with those obtained by using AAS.     

Physicochemical and Enzymatic Properties of Five Kiwifruit Cultivars during Cold Storage

Samples of Abbot, Alison, Bruno, Monty, and Hayward cultivars of kiwifruit (Actinidia deliciosa) were obtained from the Iran Research Center of Citrus (Tonekabon, located in north of Iran) and their physicochemical properties were studied during cold storage (at T = 1 ± 1 °C, RH = 80 ± 5%) at 0-, 9-, and 18-week intervals. The mean chemical composition of the fruits were as follows: ash = 0.66–0.96%, moisture = 75.2–84.7%, starch = 0.3–7.0%, and ascorbic acid = 54.8–261.0; K = 125.0–372.0 mg 100 g⁻¹ fresh weight, Mg = 18.0–32.0 mg 100 g⁻¹ fresh weight, Na = 1.4–3.1 mg 100 g⁻¹ fresh weight, Fe = 0.17–0.52 mg 100 g⁻¹ fresh weight, Cu = 0.04–0.24 mg 100 g⁻¹ fresh weight, Zn = 0.16–0.49 mg 100 g⁻¹ fresh weight, Mn = 0.04–0.10 mg 100 g⁻¹ fresh weight, and P = 25.2–49.3 mg 100 g⁻¹ fresh weight; glucose = 0.7–2.39%, fructose = 1.20–3.13%, and sucrose = 0.0–5.8%. At the same time, the values of the parameters °Brix = 6.5–14.8% and acidity = 1.8–2.5% of the studied cultivars (mutual effects of cultivar and storage time) were investigated. The increase in peroxidase (POX = 0.0–6.65 U ml⁻¹) and the decrease in pectinesterase (PE; poor activity to 0) activities were also determined. The statistical analysis showed that the Bruno cultivar had the highest content of ascorbic acid (115.0–261.0 mg 100 g⁻¹ fresh weight), which is an important compound in fruits during storage, while Hayward had the best overall quality particularly with regards to its resistance to softening. This study confirms that long-term cold storage at 1 ± 1 °C and 80 ± 5% RH is suitable for maintaining the highest quality of Iranian grown cultivars of kiwifruit.     

A Sensitive, Selective New Analytical Reagent, 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone for Extractive Spectrophotometric Determination of Mo(VI) in Food Samples

Synthesized a new reagent 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2, 6-DAPBPTSC) characterized and is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of molybdenum(VI) at pH 3.5 to form a yellowish orange colored 1:1 chelate complex. The absorbance was measured at a maximum wavelength, 500 nm. This method obeys Beer’s law in the concentration range 0.90–9.00 μg mL⁻¹ and the correlation coefficient of Mo(VI)–2,6-DAPBPTSC complex is 0.954, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 1.212 × 10⁴ L mol⁻¹cm⁻¹, 0.0079 μg cm⁻², respectively. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.894% and the detection limit value is 0.0056 μg mL⁻¹. The instability constant of the method has been calculated by Asmus’ method as 6.476 × 10^–5, at room temperature. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Mo(VI) in food and water samples. The validity of the present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which indicates the significance of the present method an inter comparison of the experimental values, using atomic absorption spectrometer.     

Properties of thermostable extracellular FOS-producing fructofuranosidase from <Emphasis Type="Italic">Cryptococcus</Emphasis> sp.

The present work was devoted to investigations concerning the fructooligosaccharide producing activity of Cryptococcus sp. LEB-V2 (Laboratory of Bioprocess Engineering, Unicamp, Brazil) and its extracellular fructofuranosidase. After cell separation, the enzyme was purified by ethanol precipitation and anion exchange chromatography. The enzyme showed both fructofuranosidase (FA) and fructosyl transferase (FTA) activity. With sucrose as substrate, the data failed to fit the Michaelis–Menten behaviour, showing a substrate inhibitory model. The K _m, K _i and v _max values were shown to be 64 mM, 3 M and 159.6 μmol mL⁻¹ min⁻¹ for FA and 131 mM, 1.6 M and 377.8 μmol mL⁻¹ min⁻¹ for FTA, respectively. The optimum pH and temperature were found to be around 4.0 and 65 °C, while the best stability was achieved at pH 4.5 and temperatures below 60 °C, for both the FA and FTA. Despite the strong FA activity, the high transfructosylating activity allowed for good FOS production from sucrose (35% yield).     

Partial Purification and Characterization of Extracellular Fructofuranosidase with Transfructosylating Activity from <Emphasis Type="Italic">Candida</Emphasis> sp.

The present work was carried out with the aim to investigate some properties of an extracellular fructofuranosidase enzyme, with high transfructosylating activity, from Candida sp. LEB-I3 (Laboratory of Bioprocess Engineering, Unicamp, Brazil). The enzyme was produced through fermentation, and after cell separation from the fermented medium, the enzyme was concentrated by ethanol precipitation and than purified by anion exchange chromatography. The enzyme exhibited both fructofuranosidase (FA) and fructosyltransferase (FTA) activities on a low and high sucrose concentration. With sucrose as the substrate, the data fitted the Michaellis–Menten model for FA, showing rather a substrate inhibitory shape for fructosyltransferase activity. The K _m and v _max values were shown to be 13.4 g L⁻¹ and 21.0 μmol mL⁻¹ min⁻¹ and 25.5 g L⁻¹ and 52.5 μmol mL⁻¹ min⁻¹ for FA and FTA activities, respectively. FTA presented an inhibitory factor K _i of 729.8 g L⁻¹. The optimum conditions for FA activity were found to be pH 3.25–3.5 and temperatures around 69 °C, while for FTA, the optimum condition were 65 °C (±2 °C) and pH 4.00 (±0.25). Both activities were very stable at temperatures below 60 °C, while for FA, the best stability occurred at pH 5.0 and for FTA at pH  4.5–5.0. Despite the strong fructofuranosidase activity, causing hydrolysis of the fructooligosaccharides (FOS), the high transfructosilating activity allows a high FOS production from sucrose (44%).     

Kinetics Modeling of Mass Transfer Using Peleg’s Equation During Osmotic Dehydration of Seedless Guava (<Emphasis Type="Italic">Psidium guajava</Emphasis> L.): Effect of Process Parameters

Peleg’s equation was used to study the effect of process parameters on kinetics of mass transfer in terms of solids gain and water loss during osmotic dehydration using 30–50% (w/w) sucrose solution at 30, 40 and 50 °C. The experimental data were successfully fitted employing Peleg’s equation with the coefficient of determination (R ²) higher than 0.88, the root mean square error, and the mean relative percentage deviation modulus (E) of less than 0.003% and 6.40% for all treatments, respectively. In all cases, initial mass transfer rate parameter (K ₁) decreased significantly (p < 0.05) as the solution concentration and solution temperature increased suggesting a corresponding increase in the initial mass transfer rate. Initial mass transfer rate followed an Arrhenius relationship which showed that solids gain had the highest temperature sensitivity (E _a = 21.93–33.84 kJ mol⁻¹) during osmotic dehydration. Equilibrium mass transfer parameter (K ₂) decreased significantly (p < 0.05) as solution concentration increased demonstrating that the equilibrium solid and water contents increased with increase in solution concentration. The equilibrium solid and water contents were also estimated adequately using Peleg’s equation (R ² > 0.78). The results of this work allow estimating the kinetics of mass transfer during osmotic dehydration in order to obtain products with determined solid and water contents.     

Thermal Degradation Kinetics of Chlorophyll in Pureed Coriander Leaves

Coriander leaves are widely used in cooking throughout the world. Thermal degradation kinetics of chlorophyll a, b, and total chlorophyll in coriander leaf puree was investigated at varying levels of pH (4.5–8.5) and processing temperature (80–145°C). Coriander puree at pH 4.5 was processed at 80° to 100°C, whereas that at pH 5.5 to 8.5 was processed at 105° to 145°C. Chlorophyll degradation followed first-order reaction kinetics. Good agreement was found between estimated and experimental chlorophyll retention in all cases (R ² > 0.80). Activation energies ranged from 6.57 to 96.00 kJ/mol. Reaction rate and activation energy data indicated that chlorophylls were more stable at alkaline pH. Transition state theory was applied to estimate the enthalpy, entropy, and Gibbs free energy of activation. Enthalpy of activation (ΔH ^#) ranged from 3.46 to 91.99 kJ/mol, whereas entropy of activation (ΔS^#) ranged from −0.265 to −0.047 kJ/(mol K). The overall free energy change was 107.55 kJ/mol. Results indicated that, the compensation effect did not exist for chlorophyll degradation in coriander puree during thermal processing.     

Flavour binding mechanism between a typical meat flavour compound (nonanal) and porcine myofibrillar proteins with consideration of conformational changes

Flavour binding or release behaviour from the meat matrix is very important for its sensory properties. The interaction between flavour substance (nonanal) and myofibrillar proteins (MPs) was investigated using protein fluorescence quenching at different temperatures. The results suggested that nonanal caused the fluorescence quenching mechanism of MPs combining dynamic and static quenching mode, and dynamic quenching played a dominant role. Nonanal mainly combined with tryptophan residues rather than tyrosine residues. The results of synchronous fluorescence spectra and circular dichroism (CD) revealed that the interaction between nonanal and MPs induced no significant conformational changes in MPs. The binding constant (K) and number of binding sites (n) (1.45–2.03) increased with temperature. The negative value of ?G (?383.16 kJ mol^?1 to ?397.30 kJ mol^?1) showed that the interaction of nonanal and MPs was spontaneous. The positive ?H (180.18 kJ mol^?1, 181.48 kJ mol^?1) and ?S (696.17 J mol^?1 K^?1, 688.32 J mol^?1 K^?1) indicated that the binding of nonanal to MPs driven by hydrophobic force.     

Aqueous solubility of calcium citrate and interconversion between the tetrahydrate and the hexahydrate as a balance between endothermic dissolution and exothermic complex formation

Aqueous solubility of calcium citrate tetrahydrate was found to decrease with increasing temperature, while solubility of hexahydrate increased with a transition temperature at 51.6 °C. Excess citrate increased calcium citrate solubility but decreased the calcium ion activity of the saturated solution with an initial solubility overshooting to form supersaturated solutions indicating binding of calcium to citrate with an association constant of 3.6 ± 0.1 × 10⁴, ΔHº = −5.07 ± 0.04 kJ mol⁻¹, ΔSº = 70.3 ± 0.3 J mol⁻¹ K⁻¹ at 25 °C. Dissolution of the tetrahydrate and hexahydrate was found to have ΔHº = 27 ± 9 kJ mol⁻¹, ΔSº = −218 ± 30 J mol⁻¹ K⁻¹ and ΔHº = 57 ± 7 kJ mol⁻¹, ΔSº = −126 ± 24 J mol⁻¹ K⁻¹, respectively, as determined from the temperature dependence of solubility corrected for complex formation. The exothermic complex formation results in inverse solubility only for the tetrahydrate with its moderate endothermic dissolution, which also precipitates at ambient temperature rather than the less soluble hexahydrate.     

Correlation between sensory and chemical markers in the evaluation of Brazil nut oxidative shelf-life

Sensory analysis is one of the most suitable processes for measuring oxidative damage and determining the shelf-life of nuts, but it is an expensive and time-consuming methodology. Thus, our objective was to correlate sensory data and chemical markers obtained during the accelerated oxidation of Brazil nuts and to determine the chemical parameters values associated with the sensory shelf-life of the nuts as established by the consumers. Brazil nuts were kept at 80 °C for 21 days. At intervals of 2 days, the oxidized odor of the samples was analyzed by nine trained panelists using a discriminative scale, and the oil was extracted to quantify the chemical parameters. A high (r > 0.95) and significant correlation (p < 0.05) was observed between the sensory data and the hydroperoxide concentration (PV), para-anisidine value (pAV), hexanal content, and α- and γ-tocopherol concentrations. When compared with fresh samples, sensory identification of oxidized odor occurred on the 4th day, noticeably earlier than changes in chemical markers (12th day). Consumers rejected the nuts after 12 days of storage, which corresponded to PV = 18.8 meq kg⁻¹ oil, pAV = 7.68, hexanal = 48.95 μmol 100 g⁻¹ oil, α-tocopherol = 15.01 mg kg⁻¹ oil, and γ + β-tocopherol = 73.88 mg kg⁻¹ oil. Our study suggests that simple spectrometric methods, such as PV and pAV, can be used to estimate the oxidative shelf-life of nuts based on sensory analysis.     

Occurrence of aflatoxin M1 in raw, pasteurized and UHT milk commercialized in Esfahan and Shahr-e Kord, Iran

Between September 2006 and September 2007, 236 samples of raw (n = 140), pasteurized (n = 48) and UHT (n = 48) milk were collected from supermarkets and from bulk milk tanks of eight dairy plants in the cities of Esfahan and Shahr-e Kord, Iran. All samples were analyzed for aflatoxin M₁ (AFM₁) contamination by ELISA and 213 (90.3%) were positive with mean concentrations 65 ng.l⁻¹. These concentrations are lower than the standards of Codex Alimentarius and FDA (500 ng.l⁻¹), but 119 samples (55.9%) had higher concentrations than the maximum tolerance accepted by some European countries (50 ng.l⁻¹). Mean concentrations of AFM₁ in raw, pasteurized and UHT milk were 68, 56, and 65 ng.l⁻¹, respectively. Mean concentrations of AFM₁ in autumn and winter samples were significantly higher (P < 0.05) than those of spring and summer but differences between AFM₁ concentrations of spring and summer samples were not significantly different. Concentrations of AFM₁ in milk from Shahr-e Kord were significantly lower (P ≤ 0.05) than those from Esfahan.     

Comparison of encapsulation properties of major garlic oil components by hydroxypropyl β-cyclodextrin

The major garlic oil (GO) components were encapsulated by hydroxypropyl β-cyclodextrin (HP-β-CD), and their encapsulation properties were compared in this study. Our results showed that the optimal conditions for the GO encapsulation were as follows: weigh ratio at 12:88 (GO: HP-β-CD), pH at 5.0, and inclusion time at 4 h. Furthermore, results from the phase solubility curves indicated that two components of diallyl disulfide (DADS) and diallyl trisulfide (DATS) had higher water solubility caused by HP-β-CD and that DATS-HP-β-CD complex had higher stability constant (K _1:1 = 6.702 × 10⁵) and more significant change in free energy ( \Updelta G_\textCOMP^* \Updelta G_{\text{COMP}}^{*}  = −3.496 × 10⁴) than DADS-HP-β-CD. These findings indicated that DATS was better suited to be encapsulated by HP-β-CD compared to DADS. The result finally obtained from gas chromatography–flame ionization detector (GC–FID) confirmed the easier inclusion properties of DATS by HP-β-CD.