Sensitive DNA-based allergen detection depends on food matrix and DNA isolation method

Performance of DNA-based methods used for allergen detection does not only depend on the real-time PCR system, but also on the DNA isolation method used. Comparison of different isolation methods showed that yield and purity of isolated DNA strongly depends on the isolation method deployed as well as on the composition of the food matrix (matrix effect). Detection of trace amounts of allergens requires efficient methods for DNA isolation which remove inhibitors and yield pure DNA. This is particularly important for quantitative analysis. Due to matrix effects, methods, which have the ability to circumvent these effects, are of great interest. Therefore, a sequence-specific method for isolation of target DNA based on magnetic particles (MCH) has been established and compared to other methods for isolation of total DNA.     

Modeling of Enzymatic Hydrolysis of Whey Proteins

The aim of this work was to emphasize the limitations of modeling complex phenomena under unrealistic model assumptions. As a case study, the whey protein hydrolysis mechanism was modeled. A stirred batch reactor was used to study the degree of hydrolysis of sweet whey protein concentrate by using the protease alcalase. A completely random two-factorial experimental design was used, three levels of initial enzyme concentrations (E ₀) (1.58, 3.18, 6.36 AU (Anson units)/L) times three levels of initial substrate concentrations (S ₀) (18.73, 38.45, 81.16 g/L). All treatments were carried out at optimal alcalase—activity conditions: pH 8 and 50 °C. Reactions were monitored for 180 min. The degree of hydrolysis (h) curves was finally adjusted for each treatment to the exponential model using nonlinear regression techniques but not assuming a Michaelis–Menten relationship. From the estimation process, the coefficient b was constant (27.26 ± 1.37) and independent of E ₀ and S ₀, while coefficient a depended directly on the ratio E ₀/S ₀, ranging from 0.0017 to 0.0497. A noncritical strategy of forward modeling based on unrealistic assumptions was misleading in the face of complex phenomena; instead, a modeling strategy moving from data to the identification and estimation of parameters of practical interest must be considered.     

Characterisation and stability evaluation of bixin nanocapsules

The aim of this study was to produce bixin nanocapsules by the interfacial deposition of preformed poly-?-caprolactone (PCL). PCL (250 mg), capric/caprylic triglyceride (400 μL), sorbitan monostearate (95 mg) and bixin were dissolved in a mixture of acetone (60 mL) and ethanol (7.5 mL) under stirring (40 °C). This organic solution was added to the aqueous solution (130 mL) containing Tween 80 (195 mg). The size distributions in the formulations with bixin concentration from 11 to 100 μg/mL were evaluated periodically during 3 weeks of storage at ambient temperature. The optimal formulation (bixin concentration of 16.92 ± 0.16 μg/mL) was characterised in terms of particle size distribution, zeta potential, bixin content and encapsulation efficiency, and showed a volume-weighted mean diameter (D_4,3) of 195 ± 27 nm, around 100% of encapsulation efficiency and the nanocapsules were considered physically stable during 119 days of storage at ambient temperature.     

Multivariate analysis for the differentiation of sparkling wines elaborated from autochthonous Spanish grape varieties: volatile compounds, amino acids and biogenic amines

The aim of this work was to focus on the study of the volatile composition of white and rosé base wines elaborated from different autochthonous grape varieties in Spain (Verdejo, Viura, Malvasía, Albarín, Godello, Prieto Picudo and Garnacha) and the evolution of the sparkling wines elaborated from them following the “champenoise” method. The amino acids and biogenic amines were also studied. Multivariate analyses (factorial and stepwise discriminant) were carried out to study the influence of these compounds all together. Base and sparkling wines from Albarín, Verdejo, Godello and Prieto Picudo were the richest in most of the volatile compounds analyzed, especially of ethyl esters and alcohol acetates, compounds that contribute to the fruity aroma of wines. During the aging on lees in the bottle of sparkling wines, an increase in branched ethyl esters, ethyl lactate and γ-butyrolactone, and a decrease in terpenes (mainly citronellol and geraniol) were observed. In general, the levels of biogenic amines in all the sparkling wines studied were very low, which does not represent a negative effect on their quality and safety.     

Pasteurization of Apple Juice Contaminated with Escherichia coli by a Combined UV–Mild Temperature Treatment

The bactericidal efficacy of ultraviolet (UV) treatments to fruit juices is limited because of their low UV transmittance; therefore, it is necessary to design combined processes to improve their lethality. This investigation was carried out to determinate the lethal effect of UV-C treatments at mild temperatures (UV-H treatments) on the UV-resistant Escherichia coli strain Spanish Type Culture Collection (STCC) 4201 suspended in apple juice. A synergistic effect was observed and the optimum temperature for the combined process was established. Subsequently, the effect of the optimized treatment on the lethality of an E. coli cocktail (STCC 4201, STCC 471, American Type Culture Collection (ATCC) 27325, ATCC 25922, and O157:H7 Chapman strain) and on freshly squeezed apple juice quality was evaluated. A UV treatment of 20.33 J/mL reached 0.61?±?0.01, 0.83?±?0.07, 1.38?±?0.04, 1.97?±?0.06, 3.72?±?0.14, 5.67?±?0.61, and more than 6 log₁₀ cycles of inactivation at 25.0, 40.0, 50.0, 52.5, 55.0, 57.5, and 60.0 °C, respectively. The optimum conditions for exploiting the synergistic effects were UV doses of 27.10 J/mL, temperature of 55.0 °C, and 3.58 min of treatment time. This treatment guaranteed more of 5 log₁₀ reductions of the cocktail of five strains of E. coli without affecting pH, °Brix, and acidity of freshly squeezed apple juice. The UV-H treatment did not increase the loss of ascorbic acid compared to the same UV treatment at room temperature but approximately doubled the inactivation of polifenoloxidase.     

Electrical conductivity and optical properties of a new quaternized polysulfone

Quaternized polysulfone with triphenylphosphonium pendant groups was investigated, as to its optical and electronic properties. Optical properties were analyzed by refractivity and transmission spectra. To obtain the optical parameters, the approach proposed by Tauc for amorphous semiconductors has been used, because of the similarity of the absorption edges. Values of pseudogap energy and Urbach energy of 3.89 eV and 168 meV, respectively, were obtained. The dielectric properties and AC-conductivity were also studied as a function of temperature and frequency. Decrease in the dielectric constant was observed with the increase in frequency and decrease in temperature. Also, quaternized polysulfone films were characterized by two relaxation processes, γ and β relaxation, which appear at different temperatures, depending on the pendant group. The frequency–temperature-dependent conductivity showed that conductivity increases with frequency and also that the quaternized polysulfones possess typical semiconducting properties. All parameters have been found as slightly influenced by the polymer chain structure.     

Wheat flour dough Alveograph characteristics predicted by Mixolab regression models

BACKGROUND: In Romania, the Alveograph is the most used device to evaluate the rheological properties of wheat flour dough, but lately the Mixolab device has begun to play an important role in the breadmaking industry. These two instruments are based on different principles but there are some correlations that can be found between the parameters determined by the Mixolab and the rheological properties of wheat dough measured with the Alveograph. RESULTS: Statistical analysis on 80 wheat flour samples using the backward stepwise multiple regression method showed that Mixolab values using the ‘Chopin S’ protocol (40 samples) and ‘Chopin + ’ protocol (40 samples) can be used to elaborate predictive models for estimating the value of the rheological properties of wheat dough: baking strength (W), dough tenacity (P) and extensibility (L). The correlation analysis confirmed significant findings (P < 0.05 and P < 0.01) between the parameters of wheat dough studied by the Mixolab and its rheological properties measured with the Alveograph. CONCLUSION: A number of six predictive linear equations were obtained. Linear regression models gave multiple regression coefficients with $R_{\rm {adjusted}}^{2} > 0.70$ for P, $R_{\rm {adjusted}}^{2} > 0.70$ for W and $R_{\rm {adjusted}}^{2} > 0.38$ for L, at a 95% confidence interval. Copyright © 2011 Society of Chemical Industry     

Variability and relationship among Mixolab and Falling Number evaluation based on influence of fungal α-amylase addition

BACKGROUND: In bread‐making technology, α‐amylase activity is routinely measured with a Falling Number device to predict wheat flour quality. The aim of this study was to determine the possibility of using Mixolab parameters to assess the Falling Number (FN) index. The effects of different doses of fungal α‐amylase addition on the Mixolab characteristics and FN index values were investigated. RESULTS: Principal component analysis was performed in order to illustrate the relationships between the Mixolab parameters and the FN index. To highlight the linear combination between the FN index values and the Mixolab parameters used to evaluate starch pasting properties (C3, C4, C5 and point differences C34 and C54), a multivariate prediction model was developed. Greatest precision (R = 0.728) was obtained for the linear regression FN = f(C4, C54) model. This model was tested on a different sample set than the one on which it was built. A high correlation was obtained between predictive model and measured FN index values (r = 0.896, P = 0.01). CONCLUSION: The model provides a framework to predict the evolution of the FN index, which is predicted by the torque for cooking stability (C4) and the difference between points C5 and C4 (C54). The obtained results suggested that the Mixolab device could be a reliable instrument for evaluation of the FN index values. Copyright © 2012 Society of Chemical Industry     

Assessment of transduction of Escherichia coli Stx2-encoding phage in dairy process conditions

In the environment, bacteriophages are regarded as natural vector for the transmission of Shiga-toxin genes among Shiga-toxin Escherichia coli strains. The possibility of transduction has been noticed in intestinal tract of various animals but experimental observations on this phenomenon in food processes are lacking. To investigate the transduction in milk at different temperature profiles and cell concentrations, an experimental plan including two different Stx₂-phages (?GV2412 and ?L34), induced respectively from E. coli O157:H7 181181/2 and E. coli O157:H7 EC34, and two recipient E. coli strains (CNCTC 6896, WG5) was performed. The donor strains were generated by lysogenization of CNCTC 6896 with ?GV2412 and ?L34 respectively. Spectinomycin resistance gene (aadA) was inserted into stx₂ operon in order to select transduced cells. Transductants were never observed at 4 °C up to 24 h, whereas after a treatment at 37 °C for 2 h and at 25 °C for 22 h they were detected in 67% of the trials with a ratio of transduction varying from 1.13 10^− 6 to 7.87 10^− 8. A treatment at 48 °C for 2 h followed by a second step at 25 °C for 22 h showed an occurrence of transduction events in only 19% of cases with a ratio of transduction varying from 2.22 10^− 7 to 2.67 10^− 8. The generation of transductants and the spontaneous induction of phages in milk were not affected by initial or final concentration of the donor or recipient strains. The results show that transduction phenomenon occurs when the cells are metabolically active and it does not take place at low temperatures. Therefore, the maintenance of the chilling chain proved to be a main factor to prevent the spread of Stx-genes in dairy processes.     

Reactivity of acrylamide with coffee melanoidins in model systems

Coffee and its substitutes have been described as complex matrices for acrylamide (ACR) analysis due to both analytical interferences and ACR instability in the matrix. Melanoidins are multifunctional and biochemically active polymers which are formed in large extent during coffee roasting. Model systems composed of ACR (elimination studies) or glucose-asparagine (ACR formation/elimination studies) with/without melanoidins was heated at 180 °C. Washed sea sand and cellulose microcrystalline were used as matrix. Coffee melanoidins had a direct influence on the fate of ACR under heating, while the effect was not observed at room temperature. In addition, ACR decrease was also related to the reaction time and the initial amount of melanoidins in the media, where clearly a dose-response was observed. In contrast, pH (from 3.5 to 7.0) had no significant effect on ACR reactivity towards melanoidins. It is hypothesized that nucleophilic amino groups of amino acids from the proteinaceous backbone of melanoidins react via the Michael addition reaction with ACR, although the exact mechanism is unknown. Then, melanoidins could modulate the reaction pathways of ACR formation and elimination during coffee roasting and serve as acrylamide-mitigation substance.