How different operating conditions of filter paper press method affect meat water holding capacity measurement

It was observed that up to now Water Holding Capacity (WHC) of meat - very important because it affects technological traits, sensory attributes and nutritional constituents - is measured using different methods, that despite many efforts over the years, do not have a sufficient standardization, essential for comparison. In particular it was observed that the application of Filter Paper Press Method by Grau and Hamm - which requires the compression of a little amount of meat on filter paper, the subsequent determination of the surfaces formed by meat and juice, and the estimation of the difference between these very areas - has suffered a lot of interpretations and adaptations. The purpose of this study is to verify if the different operating conditions (filter paper type, applied load and length of compression) could influence the results and also if they could be compared directly. For this investigation, the procedure was automated and standardised, using the BT-WHCi instrument, which applies Video Image Analysis (VIA) to area measurement. Water Holding Capacity was investigated on samples of beef M. longissimus thoracis et lumborum, pork M. longissimus dorsi and chicken M. pectoralis major. Water release was measured in different conditions considering the following factors: load applied to compress the meat (294.2, 490.3 and 588.4 N); filter paper type (Whatman 1 and 42); animal type (steer, pig and chicken) to test effectiveness of VIA, using three animals for each animal type. Area, in mm2, was measured every minute for ten minutes. Dependent variables obtained for each minute were: Total Area; Meat Area/Total Area*100 (Hoffman et al., 1982); Liquid Area = Total Area-Meat Area; Free Water (mg of H2O) = (Liquid Area/9.48) – 8 (Grau and Hamm, 1957). Every factor combination was determined in triplicates, using 250 mg of homogenised meat. The data were analysed using the SAS 8.2 package. Factorial analysis of covariance for each minute was performed on the three main factors and meat sample weight as covariate. The obtained results show that load and paper filter influenced significantly WHC values. Different applications of Filter Paper Press Method do not allow to ensure comparable data from researches. Moreover the way of measuring the area must be considered as an important source of variability (planimeter, outlining or not, VIA). At last, different formulae to express WHC complicate comparison, because they do not highlight considered factors effects, leading to different conclusions according to the parameter used, such as here evinced. In our research all those factors have been strictly controlled, so that it will be possible to define and standardize a set of working conditions and to automate it in a reliable way. The application using different animal types, in particular chicken, shows that BT-WHCi can also work under very difficult light conditions and that, last but not least, results can be directly comparable. It will therefore be possible to reassess the Filter Paper Press Method and to define the most useful operating conditions. An instrumental technique for rapid screening can be implemented to measure meat Water Holding Capacity and to improve meat quality control, of great importance for the Industry and the Consumers.