32 Feed Technology
Production of tilapia with firm, tight-grained texture flesh Specific diets change the characteristics of certain parts of the tilapia By Nie Xiao Feng, Zhong Guo Xiong and Su Shi
Indoor greenhouse facilities (top) with recirculation water tanks (left) and water treatment system.
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ccording to FAO, China produces 1.8 million tonnes of tilapia in 2016, ranking first in the world, with an export volume of 393,000 tonnes. Maoming is the main breeding area for tilapia in China and is known as the tilapia capital of China. At present, two species are mainly farmed: hybrid tilapia (Oreochromis mossambicus × O. niloticus) and Genetically Improved Farmed Tilapia (GIFT). Through a direct introduction of Nile tilapia strains from four African countries (Egypt, Ghana, Kenya and Senegal) and four Nile tilapia strains that are more widely farmed in Asia (Israel, Singapore, Thailand and Taiwan), the GIFT tilapia was selectively bred by the International Center for Living Aquatic Resources Management (ICLARM, and now known as the WorldFish Center) and other institutions.
The flesh of tilapia and grass carp are rather soft that they quickly dissipate and no longer remain in one piece during the boiling process. Therefore, the firm, tightgrained texture tilapia flesh that remains as a solid piece during cooking has a wide market demand.
Transformation of tilapia flesh
The transformation of tilapia is made by adding broad beans or faba bean to the feed. Studies have shown that broad beans can induce an increase of reactive oxygen species (ROS) in the blood, which results in cell protein and lipid peroxidation. By reducing collagen transport, it leads to an increase in collagen accumulation, thereby promoting the formation of thicker interstitial muscle fibres.
Flesh characteristics
The production of firm, tight-grained texture tilapia (known also as crispy tilapia) can be similarly compared to the production of the French foie gras where a specific diet changes the characteristics of goose liver. Why is there a market demand for firm, tight-grained texture tilapia in China?
Yu et al. (2017) reported that in the 1970s, fish farmers in Dongsheng Town, Guangdong Province, China, accidentally discovered that the muscle structure of grass carp changed significantly after they were fed only with faba bean (Vicia faba L.) and exhibited a significant increase in muscle hardness and crispiness, and thus became popular locally.
The answer is because Chinese consumers are used to eating hot pot and cooking food in boiling water. Fish is also a common ingredient in hot pot dishes. However, traditional hot pot cooking mostly uses firm, tightgrained texture species such as grouper and snakehead.
The difference between the muscle slices of ordinary grass carp and crispy carp was observed through a microscope and muscles of crispy carp showed a sturdier white texture with changes in the muscle fibre structural protein. The role of collagen is to produce good structure
September/October 2021 AQUA Culture Asia Pacific
