In our research, a composite film of whey protein isolate (WPI)/chitosan incorporated with TiO2 nanoparticles (NPs) and essential oil of Zataria multiflora (ZEO) was developed. The resulting composite films were evaluated by FTIR, SEM, and XRD, and also the physicochemical characteristics including color, mechanical properties, swelling ratio, and water vapor permeability (WVP) were studied. SEM graphs exhibited that the samples had a uniform and homogeneous structure where TiO2 NPs and ZEO were well dispersed. FTIR and XRD findings also show that the hydrogen bonds and hydrophobic interactions are the main interactions between the composite WPI/chitosan and TiO2. The crystalline nature of the composite samples increased with the increase of NP content. Nevertheless, ZEO had an insignificant effect on the functional groups and the crystallinity of composite samples. The film visual characterization revealed that, by adding and increasing the TiO2 and TiO2-ZEO, sample lightness and opacity significantly increased. Additions of TiO2 remarkably (p<0.05) improved the water vapor and mechanical properties of composite samples, although the loading of ZEO, regardless of TiO2 incorporation, led to a considerable decrement of these properties. Furthermore, composite films containing ZEO combined with 2% of TiO2 compared with 1% of NPs blended with ZEO had strong antimicrobial properties against Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes. Generally, the findings proposed that the addition of TiO2 reinforces the properties of composite films with a synergistic effect of ZEO loading on the antibacterial ability, by which the resulting biodegradable composite samples can be used as a food active packaging material.
Fresh raw shrimps were dipped for 10, 20, and 30 min at room temperature (25°C ± 1°C) in lactic acid (LA; 1.5%, 3.0%, v/v) to evaluate their antipathogenic effects against Vibrio cholerae, Vibrio parahaemolyticus, Salmonella entreitidis, and Escherichia coli O157:H7 inoculated at a level of 10(5) CFU/g. Significant reductions in the population of all these pathogenic bacteria were recorded after dipping treatments, which were correlated to the corresponding LA concentrations and treatment time. With respect to the microbial quality, 3.0% LA treatment for 10 min was acceptable in reducing the pathogenic bacteria. Additionally, sensory evaluation results revealed a 10-min dip in 3.0% LA to be more acceptable organoleptically compared with 20 and 30 min of treatments. Results of the present study are envisaged to be useful for commercial applications for effective decontamination of shrimp.
Microencapsulation is a suitable technology for incorporating active agents into a carrier. In the present study, the weight ratios of two solutions of casein and whey protein in the ratios of 70:30, 50:50 and 30:70, containing 5% by weight of betacarotene per 100g of wall material for microencapsulation were studied by spray drying method. The results indicated that samples containing 70% whey protein and 30% casein showed the best physical and chemical parameters. The results showed the efficiency of microencapsulation (70.44%), phenolic compounds (4.11 μg/mg), free radical scavenging (36.86%), dye stability of beta-carotene (75.18%) and FRAP (304.15 μmol of iron/gr). The samples revealed an upward trend during the increase in whey protein concentration. However, the particle size (11.0٩ nm) showed a decreasing trend with increasing whey protein concentration. In the following, the ratio of 30% casein to 70% whey protein was introduced as the best treatment and then added to the canola oil sample in three concentrations (200, 700 and 1200 ppm). The results indicated that the amount of polar compounds, acidic, peroxide in the oil samples during the upward trend time and the stability index has decreased. With increasing the concentration of microcapsules up to 1200 ppm, the polar content, peroxide and acid numbers were significantly lower compared to their lower concentrations. As a results, the acid number, peroxide and polar number of oil containing 1200 ppm in the lowest amount were 1.13%, 7.46 mA/kg of oil and 42.41%, respectively. In general, the results of this study showed that whey protein/casein is one of the important sources that can be used to coat bioactive compounds.
In this study, the rheological properties of Melissa officinalis seed gum (MOSG) as a function of temperature (25, 35, 45, 55, and 65°C) and salt concentrations (10, 50, 100, and 200 ppm NaCl and CaCl2) were investigated. The power law and Herschel‐Bulkley models could describe the rheological behavior of gum dispersions. The results showed that the intrinsic viscosity of the samples significantly decreased with increasing temperature and salt concentration. Steady‐state analysis of the samples revealed a non‐Newtonian, shear‐thinning behavior at tested temperatures and concentrations. The apparent viscosity increased with increasing salt concentrations and decreasing temperature. The results obtained from the frequency sweep test showed that the loss modulus (G″) values were higher than storage modulus (G′) in the concentrations of 0.25% to 0.5%, but beyond these concentrations, G′ values were greater than G″. The elasticity and viscosity of the gum samples increased with increasing concentration. The results of this study confirmed that MOSG has good rheological properties and can be used in food and pharmaceutical systems.
Practical Applications
The rheological behavior is the most important functional property of natural colloids. This property is related to the capacity of hydrocolloids in improving viscosity and the formation of gel structure at low concentrations. The thickening property of hydrocolloids has a determinant role in consumer acceptance. Furthermore, the consumer acceptance of different food products such as fruit juices, sauces, ready jells, and desserts is mainly dependent on rheological behavior. Therefore, investigation of rheological properties of the new source of food hydrocolloids is interested in food industries.
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