Comparison of Two pH Responsive Color Changing Bio‐Based Films Containing Wasted Fruit Pomace as a Source of Colorants

Abstract

The main objective of this work is to develop and characterize novel bio‐based sensor as intelligent food packaging film to monitor quality changes in fresh chicken meat. Chitosan (CS) and carboxymethyl cellulose (CMC) were used as polymer matrices for immobilization of pH sensitive color indicators. Generally considered as a food waste, blueberry (BP) and red grape skin pomace (RP) extracts were used as indicators at total phenolic content (TPC) of 0.06, 0.13, and 0.25 w/v for BP, and 0.006, 0.012, and 0.02 w/v for RP‐based films. Color, mechanical, and intelligent material properties were determined. CS films were more elastic than CMC, while no significant changes in mechanical properties occurred after the addition of both extracts at all concentrations. Notable and eye recognizable color changes in dry films were seen. It was the most significant in the pH range from 4 to 7. For CMC‐based films, color changed from violet to pink for BP extracts and from red to pink for RP extracts. For CS films, the changes were less significant. The color taint and intensity changed toward green in blueberry‐based films and to orange in grape seed extract‐based films. Significant color changes were observed after 46 hr in application tests on fresh chicken meat. This was correlated to pH changes of meat above 6 that was one of the parameters considered as an indication of spoilage. Practical Application This work provides interesting data to food industry. It offers an idea and possibility of managing food waste from fruits and vegetables industry that makes problems and costs when needed to be disposed in a proper manner. Moreover, there is the possibility of producing novel kind of food packaging materials that could be used in order to check the end of food shelf‐life in an inexpensive and natural way. Additional value lies in the fact that materials and procedures could be considered as sustainable.

Bio-Based Sensors for Smart Food Packaging—Current Applications and Future Trends

“…Synthetic dyes are commonly used such as methyl red, bromocresol purple, bromophenol blue, chlorophenol red have been proved to be able to react to pH changes when integrated into intelligent packaging systems [34,49]. Although they are demonstrated to be effective, they are not fitted to be used for food applications due to their toxic, carcinogenic, and mutagenic characteristics that threaten not only the consumers' health but also the environment [50].…”

“…The use of natural dyes instead of synthetic ones fits the consumption trend for sustainable and more natural healthy choices [49]. Natural pigments extracted from plants and fruits are renewable, demonstrate low toxicity, and low environmental impacts [50]. To be used as a pH indicator it is mandatory to consider the stability and the pH response of the pigments, which depends on each type [3,51].…”

“…Blueberry and red grape skin extracts were applied in two different matrices (chitosan and carboxymethyl cellulose) to monitor poultry meat freshness [50]. The addition of the extracts to the polymeric matrixes did not affect the mechanical properties of the films.…”

Bio-Based Smart Materials for Food Packaging and Sensors – A Review

“…Many fruits, berries, vegetables and flowers with colors covering practically the entire visible spectrum are dyed by natural compounds such as anthocyanins and curcumin known as natural pH indicators (Yoshida et al, 2009;Silva-Pereira et al, 2015;Choi et al, 2017;Dudnyk et al, 2018;Majdinasab et al, 2018;Saliu and Pergola, 2018;Zhai et al, 2018;Kurek et al, 2019). Upon protonation/deprotonation of these molecules, their delocalized electronic structure rearranges and the change of the total number of resonant electrons as well as their confinement result in a change of their color (Figure 4).…”

“…Although colorimetric pH-sensitive sensors are typically not convenient for selective analysis, it is often sufficient to evaluate the food quality based on the change of the pH, as deteriorating proteins produce alkaline volatile nitrogen compounds (cadaverine, putrescine, histamine, and ammonia) (Bulushi et al, 2009;Prester, 2011). Exploiting this indirect sensing mechanism, curcumin based indicator films, e.g., in gelatin (Musso et al, 2017) and bacterial cellulose membranes (Kuswandi et al, 2012), blueberry and red grape skin pomace in chitosan and carboxymethyl cellulose matrix (Kurek et al, 2019), chitosan-corn starch film with red cabbage extract (Silva-Pereira et al, 2015), alginate beads with red cabbage extract (Majdinasab et al, 2018) as well as red cabbage extract in pectin films (Dudnyk et al, 2018) have been shown as feasible indicators of meat, shrimp and fish spoilage by detecting amines and cyclic N-containing compounds. In a similar way, acidic CO 2 evolves during the metabolism of pathogens in the food thus lowering pH, which may be detected, e.g., by anthocyanin/polylysine in cellulose matrix in a reversible manner as demonstrated by Saliu and Pergola (2018).…”