Development of pork and shrimp freshness monitoring labels based on starch/polyvinyl alcohol matrices and anthocyanins from 14 plants: A comparative study

Anthocyanins were extracted from 14 plants including blackberry, blueberry, black eggplant, black plum, black soybean, cranberry, Chinese bayberry, grape, haskap berry, Lycium ruthenicum, mulberry, purple cabbage, purple rice and purple sweetpotato. The obtained anthocyanins-rich extracts were immobilized in starch/polyvinyl alcohol matrices to develop intelligent packaging labels for pork and shrimp freshness monitoring. Results showed the total phenolic content and total anthocyanin content of 14 plant extracts were 156.84-423.89 mg/g and 34.15-228.62 mg/g, respectively. Micro-structural characterization revealed the extracts interacted with matrices through hydrogen bonding, which slightly increased the crystallinity of labels. The extracts made labels turned violet, bluish violet, or brown. Meanwhile, the UV-Vis light blocking, antioxidant and pH-dependent color-changing abilities of labels were also elevated by extracts. Among all the labels, the label with haskap berry extract presented the highest light blocking ability, while the label with blackberry extract or blueberry extract exhibited the highest antioxidant ability. Moreover, the label with purple cabbage extract was suitable for pork freshness monitoring while the label with black eggplant peel extract or Lycium ruthenicum extract was suitable for shrimp freshness monitoring. Therefore, the micro-structural, optical, antioxidant and pH-sensitive properties of anthocyanins-rich labels were greatly influenced by the source of anthocyanins.