RESEARCH ▶▶▶
Pre-slaughter measures have knock-on effect in further processing
Water-spraying together with forced ventilation during holding improves meat quality after processing. Research shows that the water holding capacity, impedance and microstructure of breast meat from summer-transported broiler chickens is better if heat stress during holding is reduced.
BY LI ZHANG, HONGBING HUANG, PENG WANG, TONG XING AND XINGLIAN XU, POULTRY SCIENCE
T
o prolong shelf life and retain the quality of meat, freezing is the most important and widely used preservation method. During thawing, however, several changes in the meat occur, freeze-thaw wa-
ter loss being one of them. Poor water retention is influenced by the type of meat and by the freezing rate. As tissue damage is due to the formation of extracellular ice crystals, structural changes were measured by impedance characteristics using microscopic structure analysis. Often the effects of further processing procedures, such as portioning and vacuum-tumbling, are studied in relation to marinade
uptake and retention, as well as cooking loss. The effect of pre-slaughter measures has not so far been studied in rela- tion to fresh meat quality after freezing and thawing. Heat stress is just one of the factors that may lead to a deteriora- tion in meat quality, including pH, cooking loss and decreas- ing water holding capacity. Chronic heat stress results in skele tal muscle damage and reduced protein functionality, resulting in decreased yield after further processing.
Water spray cooling Heat stress in the live bird is a broiler welfare and economic issue and can be controlled by using water sprays and forced ventilation during the holding period at the slaughterhouse after transport, a practice applied in many countries during hot summer conditions. In a laboratory facility this practice was tested to determine its effect on breast meat quality be- fore and after subsequent freezing and thawing. Products treated with water spraying, forced ventilation, frozen and thawed, had the highest pH and the lowest L* value, drip and cooking loss. Compared to the fresh product, the microscopic structure of these products showed less water loss and less tissue damage as measured by the impedance method. The water spray and forced ventilation method applied to broilers after transport therefore decreases heat stress in live birds and improves meat quality after freezing and thawing.
Using forced ventilation and water spraying can prevent heat stress in broilers and have a posi- tive effect on meat quality.
▶ POULTRY WORLD | No. 6, 2020
37
PHOTO: HANS PRINSEN
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