مجله پژوهشهای علوم و صنایع غذایی ایران (Jan 2024)
Production of Whey Protein Concentrate Smart Film Containing Pomegranate and Red Grape Anthocyanin and Zinc Oxide Nanoparticles: Physicochemical and Structural Characteristics
Abstract
IntroductionEdible films and coatings are suitable for fresh, semi-processed foods, and also for processed fruits and vegetables because they can increase their shelf life, protect them from the activity of microorganisms, and ultimately improve their nutritional and sensory value. In addition, edible films and coatings are able to transfer compounds that may have been added to improve the performance of the coating film and better preserve the product or have benefits for the consumer. The present research was conducted with the aim of investigating the structural physicochemical properties of whey protein concentrate smart film containing pomegranate and red grape anthocyanins and zinc oxide nanoparticles. Material and MethodTo prepare nano composite film, 10 grams of whey protein concentrate powder was added to 90 ml of distilled water. At the beginning of the production of the film, the pH was adjusted to pH = 8 with the help of 0.1 normal soda, and in order to better dissolve the isolate, the solution was heated for 30 minutes at 80 degrees Celsius to ensure denaturation. It was then placed on a magnetic stirrer. After cooling the solution, pomegranate and red grape anthocyanins were added to the solution separately according to the statistical plan. The solution was then homogenized for 10 minutes at 13,000 rpm, and finally zinc oxide nanoparticles were added to the solution according to the statistical plan and homogenized on a magnetic stirrer for 10 minutes, and then in an ultrasound bath to disperse for 10 minutes In the next step, glycerol was added to the 40% of the weight of the dry substance and placed on a rotating magnetic stirrer without heat for 15 minutes. The formed solution was aerated for 10 minutes and 25 ml of it was poured in the center of the plate (8 cm). Then the film was dried in the oven at 38 degrees Celsius and the control film was produced. After preparing the films, the color of the film samples was determined by measuring the color components L* (lightness), a* (red/green) and b* (yellow/blue) using a Hanterlab colorimeter. The thickness of the films was measured by a digital micrometer with an accuracy of 0.001 mm at 10 random points of each film. Finally, humidity, solubility and FTIR measurement tests were also performed for the prepared films. The preparation of whey protein concentrate smart composite film was investigated based on two variables: red grape anthocyanin/pomegranate anthocyanin percentage and copper oxide nanoparticle percentage. Each of which was investigated in five levels and the response surface methodology (RSM) of the central composite design was used. A total of 24 composite films were prepared and their physical and chemical properties were investigated. Also, after analyzing the data, the optimal movies were checked based on optimization and utility function by 11 Design expert statistical software. Results and DiscussionBy increasing the amount of anthocyanin and zinc oxide nanoparticles, the thickness of the layers increased up to the middle point (0.58-0.89 mm), and the largest increase in thickness was observed in samples with 1.5 cc of anthocyanin and 2% of zinc oxide nanoparticles. Also, films with low concentrations of anthocyanin (0.1-4 cc) and a high percentage of the selected range of zinc oxide (0.2-0.7%) show the highest percentage of solubility. The added zinc oxide nanoparticles increased the solubility of the films. FTIR analysis showed that the interactions between whey concentrate and anthocyanins were probably responsible for the changes in the properties of the composite layers. The utility function for each response was estimated by numerical methods and the general utility function was obtained for the optimal samples of red grape and pomegranate. For the optimal pomegranate, the obtained results include the amount of anthocyanin equal to 2.6 cc, zinc oxide nanoparticles 0.6 (weight/volume), solubility 65.37, thickness 0.64 mm, indices a, L and bwere. 27.88 0.24 and -2.01, respectively. Finally its total desirability has been reported as 0.58. The utility function for each answer was estimated by numerical methods and the general utility function was obtained for the optimal samples of red grapes such as the optimal pomegranate. For the optimal grape film samples, the obtained results include: the amount of anthocyanin equal to 1.38 cc, 3.4 zinc oxide nanoparticles (weight/volume), solubility 59.83%, thickness 0.83 mm, a, L and b indices were 27.03, 7.05 and 1.92 respectively and, its total desirability was 0.63.
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