Preservative effects of fish gelatin coating enriched with CUR/βCD emulsion on grass carp (Ctenopharyngodon idellus) fillets during storage at 4 °C

Highlights

• CUR/βCD emulsion was used to prepare antioxidant preservation coating.

• Grass carp fillet was treated by gelatin coating enriched with CUR/βCD emulsion.

• Gelatin/CUR/βCD coating showed good preservative effects on grass carp muscle.

• A protein was identified as an indicator of deteriorated grass carp muscle.

Abstract

This study investigated the effects of a novel edible coating combining fish gelatin with curcumin/β-cyclodextrin (CUR/βCD) emulsion on the quality of grass carp fillets (GCFs) during storage at 4 °C. For all samples, the quality parameters, including weight loss, pH, total volatile basic nitrogen (TVB-N), peroxide value (PV), thiobarbituric acid (TBA) value, SDS-PAGE, free amino acids (FAA), microbiological (total viable counts (TVC), Pseudomonas counts, yeasts and molds, and H₂S-producing bacteria), color and sensorial characteristics, were tested periodically. The coatings containing CUR/βCD emulsions exhibited better preservative effects than gelatin/βCD coating. Therefore, fish gelatin coating enriched with CUR/βCD emulsion can be used as an effective way to maintain the quality of GCF and extend its shelf life during storage at 4 °C.

Introduction

Grass carp (Ctenopharyngodon idellus) is the most productive freshwater fish in China and throughout the world, and it occupies an important economic position in China's fishery market (Fan et al., 2010). Grass carp has many advantages, such as high nutritional value, palatability, short growth cycle, easy rearing and low price, all of which make it easily favored by consumers. However, grass carp fillets (GCFs) are easily susceptible to deterioration, which is mainly caused by the oxidation of fat-containing portions and proteins, the propagation of microorganisms and enzymatic degradation, even during cold storage (Sun, Sun, Thavaraj, Yang, & Guo, 2017). The putrefaction of GCF leads to sensorial, physical and nutritional quality losses, and generates off-flavors, resulting in great economic losses and health problems for consumers (Yu et al., 2018). Therefore, it is very necessary to develop effective and nontoxic preservative methods for extending the shelf life of GCF.

Bio-based coating and film preservation have been considered to be effective and eco-friendly choices for maintaining the freshness of food products and extending their shelf lives (Yu, Xu, Jiang, & Xia, 2017). Gelatin is widely used in preparing edible coatings and films, but pure gelatin coating or film has poor biological characteristics, such as antioxidant and antimicrobial abilities (Wu et al., 2018). In recent years, some natural plant extracts have been studied for their preservative effects on fish products and they are promising substitutes for synthetic preservatives (Sun et al., 2017). Curcumin (CUR) is the major bioactive compound of curcuma rhizome (Curcuma zedoaria), which has been regarded as a spice, food preservative, flavoring and coloring agent, and approved for use in food industry (Bhawana, Basniwal, Buttar, Jain, & Jain, 2011). Furthermore, extensive research has indicated that curcumin possess potent antioxidant, antibacterial, anticancer, anti-inflammatory and wound healing properties (Portes et al., 2009, Sonkaew et al., 2012, Mirzaei et al., 2018, Kant et al., 2014). However, the main problems limiting its application are poor solubility and low bioavailability. Many methods were well-developed to overcome these problems. For instance, curcumin was encapsulated in β-cyclodextrin (βCD), phospholipid, or a soy-soluble polysaccharide (Wu et al., 2018, Wang et al., 2018, Chen et al., 2017).

To our knowledge, no studies have been conducted to investigate the preservative effects of fish gelatin coating enriched with CUR/βCD emulsion on the quality of fish muscle. Hence, the objective of this study was to evaluate the preservative effects of fish gelatin coating containing CUR/βCD emulsion on GCFs during storage at 4 °C, in terms of weight loss, pH, total volatile basic nitrogen (TVB-N), peroxide value (PV), thiobarbituric acid (TBA), protein degradation, free amino acids (FAA), microbial changes, color and sensorial characteristics.