The present research is aimed at developing novel intelligent pH-sensitive films based on Persian gum and gelatin using purple carrot extract. To this end, films were developed by mixing polymer solutions containing Persian gum (5%) and gelatin (5%), in equal proportions and partially replacing distilled water of solutions with purple carrot extract at 0, 15, 30, and 45%. Total anthocyanin content, antioxidant activity, color indices, and tensile strength of films were evaluated. Purple carrot extract incorporation in the film caused a slight reduction in the lightness and an increase in the anthocyanin content, DPPH inhibition, yellowness, redness, and tensile strength. The sample containing 45% extract (anthocyanin concentration was 2.39 mg/ml) was selected as the best pH-sensitive film based on mechanical and antioxidant properties and evaluated in terms of moisture content, moisture absorption, pH, heat seal ability, thickness, contact angle, FTIR, X-ray diffraction, and colorimetric tests. The sensitivity of the film to pH changes was assessed in the range of 2-12. The color of the film changed from pink to blue as a function of pH. The results proved that films based on Persian gum, gelatin, and purple carrot extract could be used as novel food grade biomaterials to monitor the freshness/spoilage of food.
This research reports the first application of the reverse spherification (RVS) method for encapsulation of two probiotics (Lacticaseibacillus rhamnosus GG and L. plantarum 299 V) compared to the basic spherification (BS). These probiotics were encapsulated in different solutions encompassing various contents of alginate, gelatin, and gellan gum. The RVS bead diameters was about 1.5 times bigger and hardness was 70%–80% lower than BS samples. As determined by Raman spectral mapping, the RVS beads had two calcium alginate walls but the BS beads had only one. The inner wall of the RVS beads was more than three times thicker than outer wall. The encapsulation yields of gelatin/gellan gum and gelatin beads prepared by both methods were >1.5% alginate beads. All the RVS-prepared beads were resistant to stomach acid and showed no significant reduction in the intestine. Furthermore, the incorporation of gelatin and gellan gum into alginate led to higher cell protection. For 1.5% alginate beads, <67% survival was achieved after acid exposure but in others, >77% survival was observed; RVS beads were about 1 log above than BS ones. The proposed novel microencapsulation method efficiently increased the viability of probiotic bacteria compared to the conventional approaches.
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