Characteristics of gelatin from pig skin waste; effect of different organic acids used on pre-thermal treatment

Abstract Upcycled products prevent food waste and contribute to a sustainable solution to obtain novel by‑products. This research paper presents the properties and characteristics of gelatin obtained from pig skin waste using different organic acids solutions as a pretreatment that have been studied. The pH, hydroxyproline content (Hyp), the thermal properties and the color of the product were evaluated. All acids used are food-grade acids. There were differences the gelatin yield showed among the food‑grade acid solutions pretreatment, Acetic (AH), Latic (AL), Citric (AC) and Ascorbic acid (AA) (0.5M). AH and AA treatments resulted in higher gelatin Hyp content than AL and AC. The pH of each gelatin solution was 3.46, 3.10, 2.76 and 2.30 for AH, AA, AL and AC, respectively. The AH showed two gel-sol thermal transitions at 57.8°C and 127.5°C while treatments AL, AC, and AA showed only one thermal transition at 122.9°C, 121.4°C and 97.2°C, respectively. The DSC enthalpies energies result in differences between gelatin-films. The acid pretreatment affected the brightness of the gelatin-films and the color parameters. The lowest lightness resulted from AA, and the highest a* and b* color parameters were observed in the AC gelatin‑film. The results showed that the use of food-grade acids to obtain gelatin from waste pig skin is promising. Moreover, a good Hyp content can be obtained from all such treatments. The food‑grade acids used affect the gelatin thermal, gelation and color properties. The results suggest that the acid pretreatment causes substantive changes in protein functionality.