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肉禽类

Monitoring of physical–chemical and microbiological changes in fresh pork meat under cold storage by means of a potentiometric electronic tongue

1.Introduction

Meat freshness is a rather complex concept, which includes different microbiological, physicochemical and biochemicalattributes and that is related with two different processes. One, desired,is known as a ging that is determined by the period of storage that meat (especiallybeefmeat) needs in order to reach the optimum state of consumption; where as the other, also related with storage, deals with meat spoilage due to bacterial growth and autolysis. Traditionally, the rehave been two methods to evaluate meat freshness; one consist so fasensory test controlling or ganoleptic attributes with the help of experts and the other is the chemical or biochemical determination of the concentration of target bioindicators.

2.Materials and methods

2.1.Raw material

All the experiments using the electronic tongue and the bio-chemical determinations were carried out on a three wholepieces of porkloin. The pork loins were obtained from a local slaughter-house with 1 day postmortem. Samples were obtained from female pigs(crossbreedsLandrace  LargeWhite) sacrificed with anaverage live weight of 130kg. During the experiment alprocess, the meat was store dunder refrigerationata temperature of4 C.Everyday, two slices of each loin were cut, one for the potentio-metric measurements and one more for the corresponding bio-
chemicalanalysis(videinfra).

2.2.Electrochemical measurement, data acquisition and computing tools

The complete measurement equipment was built up for this specific application and wasformed by several blocks including:the electrodes, the signal conditioning system, the data acquisition system and tools for the multivariate analysis of the data.

2.3.Electrodes
Theelectronictongueconsistsofasetofsixelectrodesofdiffer-entmaterials:i.e.gold,silver,cooper,lead,zincandgraphite.The
engthofeachelectrodewasabout3cmwhereasthethicknessvariesdependingonthematerialused.Theelectrodesweresol-
deredtoaprintedcircuitboardthatservedtosupporttothewholesystem.Throughacentralholeintheboardacalomelreference
electrodewasalsoincorporatedtothesystem.Asimilarsetofelec-trodesandconfigurationhasbeenusedpreviouslyinotherappli-
cations(Giletal.,2008).

3.Results and discussion

3.1.Potentiometric measurements

3.2.Multivariateanalysis


3.3.Classification with artificial neural networks


3.4.Chemical and biochemical analysis

3.5.Measurement of pH

3.6.Microbial growth

3.7.Measurement of nucleotides produced by the decomposition of ATP

3.8.PLS analysis



4.Conclusions

The potentiometric data of certain metallic(Au,Ag,Cu,Pband Zn) and graphite electrodes have demonstrated to show avariation versus time when in contact with a piece of pork loin. Additionally, PCA and neural network analysess how edthat is was possible to determine the post-mortem time elapsed by using the sesimple potentiometric measures and rather conventional electrode ssuggesting that such an easy device could be employed forth edetermination of freshness in meat. Data from the electronic tongue were additionally compared with other well-known methods for
the evaluation of freshness based on the determination of the concentration of certain biomolecules as a function of time after death. A relatively good correlation was found between the response of the electronic tongue and certain degradation in dexes such as the pH, microbialcount and nucleoside concentrations.