Inhibition of melanosis of Patagonian shrimp using chitosan coatings

MARTINA FIEDOROWICZ KOWAL; ORTIZ NICOLAS; DIMA JIMENA

Congreso; 11th WORD CONGRESS OF CHEMICAL ENGINEERING; 2023

Patagonian shrimp is one of the most important marine resources in Argentina. However, the shelf life of shrimp is limited due to melanosis (black spots) and quality deterioration during storage. These black spots appear immediately after capture limiting their market value. To retard melanosis, antimelanosic agents, such as sodium metabisulfite (SM) are used. However, the use of SM is being limited due to their potential toxicity. Chitosan (CH) is a non-toxic and biodegradable biopolymer obtained from shrimp shells. CH has several features such as film formation, and antimicrobial and antibrowning effects [1]. Their properties and its ability to form edible coatings, could be used to replace SM totally or partially. The aim of this study is to evaluate the effect of chitosan coating on the melanosis, quality parameters and sensorial attributes of Patagonian shrimp (P. muelleri) during 7 days of ice storage.Chitin was obtained by decalcification and deproteinization of shrimp shells. Chitosan was obtained by deacetylation of chitin with 50% NaOH. CH solution (0.75%) was prepared by dissolving into 1% acetic acid, then glycerol (5%) was added, as plasticizer, into CH solution with stirring for 30 min. SM and ascorbic acid (AA) were used as additives in the polymer solution to evaluate different edible coatings. Patagonian shrimps samples (without SM) were randomly divided into six groups and were dipped for 10s into: (I) Control (uncoated), (II) 0.25%SM solution, (III) CH solution, (IV) CH-0.25%SM solution, (V) CH-0.125%SM solution, and (VI) CH-0.05%AA solution. After dipping, the shrimp were drained and air-dried at ambient temperature for 3 min in order to form the coating. All samples were conditioned in ice and stored at 4°C. The shrimp were photographed every 24h to evaluate the appearance of melanosis. Quality parameters and sensory attributes were measured every 48h for 7 days: a) pH, b) Weight loss, c) Moisture content, d) Water holding capacity, d) TBARS test, e) Instrumental color, f) Total mesophilic counts. Sensory attributes and evaluation of melanosis score were carried out by five trained panelists using a SENASA scale. The photographs showed that treatments with CH, SM, and both CH-SM retarded the appearance of melanosis until day 5. However, shrimps with CH-AA coating showed melanosis at day 3. The values of pH, weight loss, and moisture content showed no differences within treatments. The TBA values of all treatment were significantly lower than the control samples after day 5. Treatment with CH, SM, and both CH-SM inhibited microbial growth until day 5. Finally, shrimps with CH, SM and CH-SM coatings obtained higher sensory scores than control shrimp, which is consistent with the changes of melanosis score. This study showed that treatment with CH and CH-0.125%SM had similar results than 0.25%SM and CH-0.25%SM, indicating a synergistic effect which could allow the reduction of SM concentration currently used in the fishing industry.