Salt Uptake and Water Loss in Hams16 November 2013
The salt uptake homogeneity is crucial in assuring quality in dry-cured hams.
And according to a series of studies from IRTA in Spain, the duration of storage before salting as well as the temperature during salting both have relevant effects on salt absorption.
In Mediterranean countries, the traditional elaboration process of dry-cured ham has three fundamental stages: dry-salting, resting and drying/ageing.
During the salting stage, the amount of salt absorbed by the hams is often highly variable.
The amount of salt affects the drying process and the biochemical reactions during the whole process, such as proteolysis and lipolysis, which are in part responsible for the quality of the dry-cured ham.
Therefore, the variability in the salt absorption causes heterogeneous behaviour of the hams throughout the next stages of the process, hindering their control, and obtaining final products with heterogeneous sensory and nutritional characteristics which could also negatively influence the purchase decision of consumers.
The study said that there is a current tendency to reduce the salt content in dry-cured hams in line with the recommendations from the World Health Organization to reduce sodium dietary consumption.
However, the reduction of added salt, without a previous reduction of the variability in salt absorption, results in a higher percentage of hams showing both quality and microbial stability problems due to insufficient salt content.
Salting can be explained as a two phase process.
In the first phase, NaCl is dissolved on the ham surface which results in brine but some water on the lean surface is necessary to initiate the salting process.
In the second phase, the Cl− and Na+ ions from the brine diffuse towards the internal part of the meat.
Factors affecting these two phases are, therefore, expected to contribute to the salt uptake heterogeneity.
Before salting, hams are stored in cold rooms for different periods of time (from hours to several days) due to differences in transport and processing time schedules.
The duration and the conditions of storage until salting may affect the water content at the lean and rind surfaces, which in turn could affect the salt uptake during salting. Moreover, the temperature and relative humidity of the salting room can also affect the hydration level of NaCl.
Temperature during salting is set below 5 °C to reduce microbiological growth, but over 0 °C to avoid freezing.
Although temperature is maintained within a narrow range of values, temperature variation can also contribute to the salt uptake variability.
When the temperature of the salt in the salt pile is below 0.15 °C and the water contained in the salt-water mixture is below 38.1 per cent, the NaCl hydrates and crystals of NaCl • 2H2O are formed.
The formation of these crystals on the lean surface of the hams can affect salt absorption.
The temperature also affects the salt diffusion in the meat matrix.
However, the IRTA studies were focused on a higher range of temperatures (from 3 °C to 40 °C), which represent only a part of the temperatures used during the salting process.
The effect of temperatures closer to the freezing point of meat (− 1.5 °C), which produces the maximum reduction in bacterial growth in fresh meat, has not yet been studied.
The aim of the study by Núria Garcia-Gil, Israel Muñoz, Eva Santos-Garcés, and Jacint Arnau, Pere Gouwas to evaluate the effect of the water contents at the lean surface before salting and of the temperature during salting on the salt uptake.
Pieces of loin stored at 3 °C for three days before salting absorbed less salt through a surface that has been dried during storage.
A group of raw hams were subjected to different pre-salting storage times (zero, three and six days) and another group subjected to different set room temperatures during salting (− 1.0, 0.5 and 4.0 °C).
The duration of storage before salting and the temperature during salting had a negative and a positive effect on the average salt absorption, respectively.
The duration of storage before salting as well as the temperature during salting tested in the study had relevant effects on salt absorption although no particular condition reduced the variability in salt uptake within batches.
The most important effect of pre-salting storage appeared at six days of storage and the most important effect of salting temperature was observed at 4 °C.
Therefore, pre-salting and salting conditions should be controlled to reduce the variability in salt uptake between batches, especially when storage times longer than three days and salting temperatures above 0.5 °C are used.
No significant differences in salt uptake homogeneity were found between storage times and between salting temperatures.
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