جستجوی مقالات مرتبط با کلیدواژه « Magnetic nanoparticles » در نشریات گروه « صنایع غذایی »

Milk, from its production to consumption, is exposed to a variety of microbial and chemical contaminants. Aflatoxin M1 (AFM1) is one of the most important contaminants in milk, which has always received attention due to its carcinogenic and destructive effects on the consumer. Accordingly, the rapid, sensitive, and cost-effective identification of AFM1 in milk is essential. In the present paper, an electrochemical aptasensor based on screen printed electrode (SPE) modified with magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) was proposed to identify AFM1 in cow milk samples. SPE was activated by applying a potential within the range of -1.5 to +1 V versus the reference electrode at a scan rate of 200 mV/s for 5 continuous cycles in the 0.5 M sulfuric acid and 0.1 M potassium chloride solution. Changes of the electrode surface at different stages of preparation were assessed using cyclic voltammetry (CV) technique. Using CV in optimal conditions, it was found that the aptasensor presents a concentration range of 100-700 ng/l and a limit of detection (LOD) of 50 ng/l.  There was a linear relationship between changes of the current peak (∆I) and analyte concentration. This relationship follows the regression equation of ∆I=0.0209C+2.14 (R²=0.9897). Calculation of the relative standard deviation (RSD=3.2%) indicated the acceptable repeatability of the electrochemical aptasensor. The current peak was obtained to be 7.4% in the investigation of RSD reproducibility, indicating the good reproducibility of the electrochemical aptasensor. The obtained results showed that the aptasensor response after 8 days has only reduced by 7% compared to the first day, indicating the desirable stability of the aptasensor. The recovery percentage range for cow milk samples at concentrations of 100 and 200 ng/l was obtained to be 86.5 and 93%, respectively, showing the acceptable recovery percentage of the electrochemical aptasensor.

The aim of this study was to investigate the effect of immobilized glucose oxidase on magnetic chitosan nanoparticles on the content of organic acids (lactic acid and acetic acid), viability of probiotic bacteria and sensory properties of probiotic drinking yogurt. Different concentrations (0, 250, 500, 750 and 1000 mg/kg) of free and immobilized glucose oxidase were used in probiotic drinking yogurt. The samples were stored at 4˚C for three weeks. During storage, the content of acetic acid, counts of Lactobacillus acidophilus and Bifidobacterium lactis decreased and the content of lactic acid increased significantly (p<0.05). Addition of enzyme increased the viability of probiotic bacteria in test samples as compared to control sample (without enzyme). The viability of Bifidobacterium lactis in the samples containing high levels of enzyme (750 and 1000 mg/kg) was higher than other levels. The samples containing 500 mg/kg of free and immobilized enzyme had the highest count of Bifidobacterium lactis (7.88 log CFU/mL) and the amount of acetic acid in these samples (0.82 and 0.87 g/L, respectively) was more than other samples. There was no significant difference between the samples in regards to sensory properties. Therefore, addition of glucose oxidase immobilized on magnetic chitosan nanoparticles can decrease oxidative pressure and create suitable condition for the viability of probiotic bacteria in drinking yogurt and maintain overall acceptability. Moreover, it is economically feasible.

Inulinase can produce high fructose syrup from inulin in a one-step enzymatic process. In this research, Inulinase was immobilized on the magnetic nanoparticles functionalized with protein and peptide nanoparticles through covalent attachment to improve the stability of the enzyme. At the first step, the magnetite nanoparticles were prepared by co-precipitation method. Then, in the second step, a mixture of soy protein isolate and bovine serum albumin nanoparticles, and wheat gluten hydrolysates prepared by endopeptidases were synthesized by desolvation method and then the magnetite nanoparticle’s surface were coated for modification and stabilization. In The third step, the enzyme was immobilized on the surface of the magnetite carrier by using of glutaraldehyde. In this study, scanning electron microscope (SEM) and dynamic light scattering (DLS) were used for analyzing the particle size, shape, morphology and functional characteristics of magnetite and protein nanoparticles and enzyme immobilization in all steps of preparation. After enzyme immobilization the functional properties were compared with the free enzyme. The results implied that thermal stability and resistance to acidic pH were increased. The activity of the enzyme, reusability, and kinetic parameters (Vmax, Km, t1/2) were assayed and the results revealed better operational stability compared to free enzyme