Active packaging and colour control: the case of meat 409 Table 19.3 Packaging and storage conditions used in the models developed in Moller er a.(2003) Modelling factor Abbreviation No of levels etting of levels Storage time( days) 1,3,6,9,14 esidual O2 level (%% Reso2 53-3322 0.1,0.25,0.5 Measured O2 level (% MeasO2 ontinuously Oxygen Transmission OTR 0.5,10,32 Rate(ml/m /24h/atm) Volume ratio l:1,1:3,1:5 (product to headspace) Light intensity(Lux) Light Nitrite content(ppm) Nit 19.3.2 Optimising colour stability of cured ham When packaging cured meat products it is important to keep the O2 and light exposure at a minimum to prevent photo oxidation of nitrosylmoglobin. Moller et al.(2003)investigated the colour stability of cured ham under different packaging and storage conditions according to Table 19.3. Colour measurements were performed with a Minolta Colorimeter using the a-value to express the red colour of the product. The effect of light was evaluated as the light intensity from a fluorescent tube measured on the package surface The resulting model(after removal of insignificant effects)considering only two-factor interactions is shown in equation 19.8 a-value=+61·ResO2+B·Vol+ 63 Light+B4·Nit+Bs:Time 6· Measo2+所Res)2· Light+g·ResO2·Time+A·ResO2 Measo2+A1o·Vol· Measo2+B· Light· Measo2+B12:Time 19.8 where betas are regression coefficients As expected, the a-value decreases with increased time, increased residual O2 level, increased OTR, increased light intensity and decreased nitrite content. However the study also shows the importance of interactions between factors. The interaction between O2 level and product to headspace volume ratio is especially interesting. Normally, the focus is on the residual O2 level (%)in the package and it is commonly overlooked that also the total amount of available oxygen molecules is important. The total amount of oxygen molecules available for colour deteriorative reactions is determined by the residual oxygen level after packaging, the meat to headspace volume ratio, and the amount of oxygen that permeates into the package headspace in combination. It is not sufficient to keep a low O2 level in the package headspace. If the headspace volume is large there will still be plenty of oxygen molecules for colour deterioration19.3.2 Optimising colour stability of cured ham When packaging cured meat products it is important to keep the O2 and light exposure at a minimum to prevent photo oxidation of nitrosylmoglobin. Møller et al. (2003) investigated the colour stability of cured ham under different packaging and storage conditions according to Table 19.3. Colour measurements were performed with a Minolta Colorimeter using the a-value to express the red colour of the product. The effect of light was evaluated as the light intensity from a fluorescent tube measured on the package surface. The resulting model (after removal of insignificant effects) considering only two-factor interactions is shown in equation 19.8. a-value ˆ 0 ‡ 1
ResO2 ‡ 2
Vol ‡ 3
Light ‡ 4
Nit ‡ 5
Time ‡6
MeasO2 ‡ 7
Res)2
Light ‡ 8
ResO2
Time ‡ 9
ResO2
MeasO2 ‡ 10
Vol
MeasO2 ‡ 11
Light
MeasO2 ‡ 12
Time
MeasO2 19:8 where betas are regression coefficients. As expected, the a-value decreases with increased time, increased residual O2 level, increased OTR, increased light intensity and decreased nitrite content. However the study also shows the importance of interactions between factors. The interaction between O2 level and product to headspace volume ratio is especially interesting. Normally, the focus is on the residual O2 level (%) in the package and it is commonly overlooked that also the total amount of available oxygen molecules is important. The total amount of oxygen molecules available for colour deteriorative reactions is determined by the residual oxygen level after packaging, the meat to headspace volume ratio, and the amount of oxygen that permeates into the package headspace in combination. It is not sufficient to keep a low O2 level in the package headspace. If the headspace volume is large there will still be plenty of oxygen molecules for colour deterioration. Table 19.3 Packaging and storage conditions used in the models developed in Møller et al. (2003) Modelling factor Abbreviation No. of levels Setting of levels Storage time (days) Time 5 1, 3, 6, 9, 14 Residual O2 level (%) ResO2 3 0.1, 0.25, 0.5 Measured O2 level (%) MeasO2 – Continuously Oxygen Transmission OTR 3 0.5, 10, 32 Rate (ml/m2 /24h/atm) Volume ratio Vol 3 1:1, 1:3, 1:5 (product to headspace) Light intensity (Lux) Light 2 500, 1000 Nitrite content (ppm) Nit 2 60, 150 Active packaging and colour control: the case of meat 409