The effect of different melanosis-inhibiting blends on the quality of frozen deep-water rose shrimp (Parapenaeus longirostris)

Highlights

• 4-Hexylresorcinol-based formula prevented melanosis in frozen shrimp.

• Gluconic acid, chitosan or glucose are good coadjutants in browning-inhibiting blends.

• Hardness and water holding capacity of shrimps were not affected during storage.

• Formulations with 4-Hexylresorcinol reduced the total microbiota after treatment.

• All formulations preserved sensory, functional and microbial quality in frozen shrimp.

Abstract

The influence of different melanosis-inhibiting formulations on sensory parameters, texture, water holding capacity and microbiological properties of frozen deep-water rose shrimp (Parapenaeus longirostris) was evaluated throughout 6 months of storage at −18 °C. Eight formulations were tested: three of them containing 4-hexylresorcinol (4-HR, 0.05, 0.1 and 0.25%, w/v) in combination with organic acids (citric, ascorbic and acetic) and chelating agents (ethylenediaminetetraacetic acid and di-sodium di-hydrogen pyrophosphate); four commercial formulae based on sulphites (alone or accompanied by gluconic acid, chitosan or glucose), and a commercial blend based on 4-HR and NaCl. Non-treated shrimp were used as control. 4-HR-based treatments, as well as the joint use of sulphites and d-gluconic acid, were very effective in preventing melanosis during storage without affecting sensory parameters. All formulations assayed did not alter the water holding capacity of muscle protein during frozen storage. In general terms, shrimp hardness increased after a melanosis-inhibiting blend treatment and remained more or less constant during storage. From the microbiological point of view, experimental formulations with 4-HR reduced the total microbiota after treatment, especially at 0.1% (w/w). After 6 months of frozen storage, for most microbial groups studied counts were lower than the limit of detection, except in shrimp treated with the commercial 4-HR-based formulation, where counts were close to 3 log cfu/g. The melanosis-inhibiting blends assayed were useful to preserve sensory, functional and microbial quality in shrimp after six months of frozen storage.

Introduction

Deep-water rose shrimp (P. longirostris) is a highly appreciated crustacean captured in the Atlantic Ocean, mainly in the Gulf of Cadiz, in Morocco and in some areas of the Mediterranean Sea. Due mainly to market price and limited habitat, deep-water rose shrimp is not the most consumed species worldwide, yet it is the most sold crustacean in retail establishments in Andalusia (Spain). In Spain the market price of fresh deep-water rose shrimp has increased by a 25–50% in the past five years, reaching an average range of 15–50 euro/kilo in 2018, depending on the size. This shrimp is also commercialized cooked and/or frozen.

Deep-water rose shrimp are usually captured by small fishing boats which are rarely equipped with freezing chambers. Thus, fishermen must preserve captures refrigerated or stored in crushed ice boxes until reaching port. When deep-water rose shrimp are frozen inland, the delay in freezing can irreversibly affect quality, as melanosis develops very quickly in this crustacean species. Moreover, deep-water rose shrimp inhabit in cold water and deteriorate faster than warm-water species during ice storage, as documented by Goncalves, López-Caballero, and Nunes (2003). The optimum way to maintain and commercialize this species is at temperature approaching that of melting ice (close to 0 °C) according to Regulation (EC) No 853/2004; still, at times they require to be frozen for long distance transport, as it is the only way to avoid spoilage.

Melanosis is considered a limiting factor for crustacean preservation. This alteration originates by the action of polyphenol oxidase (PPO) and in some species, as deep-water rose shrimp, also by the action of activated hemocyanin (Adachi, Hirata, Nagai, & Sakaguchi, 2001; Martínez-Alvarez, Gómez-Guillén, & Montero, 2008). PPO and activated hemocyanin oxidize phenolic compounds to quinones that spontaneously polymerize forming very high molecular weight pigments. Such pigments are not considered to be harmful to health; however, they devalue the commercial quality of the product. Melanosis-inhibiting blends, mainly those based on sulphite derivatives, are usually added after capture in order to avoid the appearance of black spots beneath the cuticle. Nevertheless, there is certain controversy related to the doses recommended by manufacturers and the legislated residue limit in the edible portion of the crustacean, which often results in a high percentage of seizures. This fact, together with the occasional allergies and asthmatic episodes in certain population groups associated with the consumption of treated seafood (Vally & Misso, 2012), makes the search for new food-grade melanosis-inhibitors relevant. In this regard, 4-HR is viewed as an interesting alternative to sulphites in crustacean treatment. This compound is deemed GRAS (Generally Recognized as Safe) in the United States, where its commercial use for food purposes is allowed. In the European Union, the use of 4-HR as an antioxidant has been approved in fresh, frozen or deep-frozen crustacean meat, but maximum residue levels in the edible portion of the crustacean cannot exceed 2 mg/kg. Some studies support the effectiveness of 4-HR preventing melanosis in fresh crustaceans, including deep-water rose shrimp (López-Caballero, Martínez-Álvarez, Gómez-Guillén, & Montero, 2006b; López-Caballero, Martínez-Álvarez, Gómez-Guillén, & Montero, 2019). The use of polyphenols to avoid the appearance of black spots is another possibility that has received some attention among researchers (Nirmal, Benjakul, Ahmad, Arfat, & Panichayupakaranant, 2015; Sae-leaw & Benjakul, 2019). Chitosan dissolved in an acid medium has also been reported to be useful as a melanosis inhibitor (Simpson, Gagné, Ashie, & Noroozi, 1997), as well as the enzymatic glucose oxidase/catalase solution (Dondero, Egaña, Tarky, Cifuentes, & Torres, 1993).

Nearly all studies published on crustacean melanosis have been developed in refrigeration, where the appearance of blackening may occur within a few hours after capture. As a consequence, sometimes melanosis-inhibiting blends are added in excess. However, the distribution and consumption of frozen crustaceans constitutes a much larger market volume than that of fresh seafood and therefore, the negative impact of melanosis may have great economic significance. There is scarce information available on PPO activity in frozen crustaceans and its implication in melanosis, and there is even less information about the effect of melanosis-inhibiting formulations applied before freezing.

During frozen storage, protein denaturation frequently occurs as a consequence of the formation of ice crystals, dehydration and solute concentration in the tissues. This negatively affects the functional properties of myofibrillar proteins, characterized mainly by loss of water retention capacity and variations in muscle texture. Some physicochemical and functional properties of proteins during frozen preservation have been studied in different shrimp species (Jiang, Hwang, Chen, & Moody, 1991; Srinivasan, Xiong, & Blanchard, 1997); nevertheless, the effect on deep-water rose shrimp is not known.

The aim of this work was to investigate the influence of different melanosis-inhibiting formulations on sensory parameters of deep-water rose shrimp (P. longirostris), frozen after capture and preserved at −18 °C for 6 months. A second objective was to determine the effect of those formulations on texture, water holding capacity and microbiological properties of frozen shrimp.