Biochemical and nutritional evaluation of mangrove clam Anadontia edentula from Pattuvam and Kattampally, Kerala, India

Introduction

Clams and other bivalves are good source of protein among the riparian communities, especially in the South-East Asian countries. Their collection, marketing and utilisation is a source of livelihood and a considerable number of women are engaged in the collection, processing and marketing. Man-made issues like sand mining, pollution and conversion of beaches and mangrove areas are threats reported for destruction of clam beds. Difficulty in cleaning and processing due to smaller size is a reason for less consumer preference compared to other seafoods. Mangrove clam, Anadontia edentula is a bivalve distributed in Indo-Pacific, from East and South Africa, including Madagascar and the Red Sea, to eastern Polynesia and Hawaii, and from southern Australia to northern Japan (Palomares and Pauly, 2025) [4] . The mangrove clam A. edentula is highly prized in the Philippines for its flavour and large size (Primavera et al, 2002) [5] . Mangrove clams are collected and consumed after boiling, removing the shell, and preparing curry. Meat is very hard and it needs to be pressure-cooked, unlike other clams, for the preparation of the curry and that may be the reason for the lack of interest in the collection and utilization of the species. There is limited literature available on occurrence, collection and utilization of this species (Rathul et al, 2023) [7] . Furthermore, proximate composition, storage and utilization in India are entirely absent (Rathul, 2022) [6] . Hence, the present study assumes considerable significance for the species.

Materials and Methods

The study on mangrove clam A. edentula was conducted from mangrove forests of Kannur, extending from Kattampally to Pattuvam of Kerala with the help of local fisherfolk during low tide in the post-monsoon season during the year 2021-2022.

To compare and evaluate the nutritional and organoleptic characters of mangrove clam, samples of black clam (Villorita cyprinoides) was collected from local markets and selected as the control. Then the shells were open, meat was scooped out using a small shucking knife. The weight of the meat content was also measured to know the wet weight and yield in the field. The moisture content was determined by the oven drying method and the fat content of the moisture-free sample is determined by extracting the fat with a suitable solvent (AOAC, 2012) [2] . Ash content, total nitrogen and amino acid was analyzed according to the standard method described by AOAC (2005) [1] . Organoleptic evaluation of sausage was done by a group of panellists' who were asked to evaluate the product by giving scores for appearance, colour, taste, texture, odour, and overall acceptability of the samples fried in refined vegetable oil based on 9-point descriptive scale (ranges from 1 for low to 9 for high).

Results and Discussion

Proximate composition of mangrove clam is given in Table 1, which shows that the moisture content is 8%, followed by protein content of 10%, Fat at 5%, and Ash at 5%. A recent report on food composition per 100g edible portion of mangrove clam was estimated as Water (g) 82.3, Protein (g) 6.8, Fat (g) 0.8, andAsh (g) 2.8. The proximate composition of products displays slight variations across their compositions depending on species. The ash and moisture content after deep and flash frying of common clam nuggets was comparatively higher than mangrove clam nuggets, whereas the protein content was higher in mangrove clam's nugget than in the control product.

Similarly, the fat content was significantly higher in the control product. Sensory evaluation of Clam products: Sensory assessment is one of the best methods for quality control which does not require any expensive chemicals and testing equipment, more over the sense of sight, smell, touch, and taste can be used for analysis. The result will be a combination of multiple unbiased opinions from a trained panel of individuals who critically analyzed the product using their senses. The present study provides the detailed biochemical and nutritional evaluation of the mangrove clam Anadontia edentula collected from selected mangrove ecosystems of Kerala, India. The study reveals that the species contains appreciable levels of protein (11.16%), fat (8.01%), essential amino acids, when processed into value-added products.

These results highlight the nutritional potential of A. edentula as a seafood resource that remained unknown due to its tough texture and limited consumer familiarity. Though having high potential many clams such as the Asian hard clam is not popular for consumption in Thailand, owing to a high amount of mucus and a tough texture (Karnjanapratum, et al, 2013) [3] . Biochemical composition and nutritional evaluation of common clams are reported but similar data with respect to A. edentula is not available as the availability of the latter is restricted to certain pockets. The results of proximate composition, amino acid profile, fatty acid content, and sensory quality shows scope for future investigations for value addition and product development.

References

1. clam (Linnaeus, 1758) from selected areas in North Kerala [dissertation]. Cochin: Cochin College; 2022, p. 33.
2. Remesh R, Renjith RK, Zynudheen AA, Raman MM. Length-weight relationship of mangrove clam Anodontia edentula (Linnaeus, 1758) from Kattampally, Valapattanam River, Kerala, India. Fish Technol. 2023;60:286-289.