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Effect of packaging and display variables on retail display of frozen lamb chops
Meat Science22 (1988) 313-320
ResearchNote Effect of Packaging and Display Variables on Retail Display of Frozen Lamb Chops
ABSTRACT Display conditions ofpackaging and lighting and the length offrozen storage of the carcass before cutting were examinedfor their eflect on the colour of frozen chops during display. Lighting eflected a greying and loss of saturation of the colour, while packaging$lm affected brightness and hue angle. Length of storage aflected hue and saturation. Display time afleeted brightness and hue in a linear manner.
INTRODUCTION
For over 100years,New Zealand has marketed lamb overseasin the form of frozen carcasses.In recent years,however, the New Zealand meat industry has started to export frozen consumer cuts, and the performance in the market place of thesecuts has becomeof vital interest.This paper reports on the effectsof carcassstoragetime, packaging film, and lighting conditions on the colour retention of displayed frozen lamb chops. MATERIALS
AND METHODS
Carcass and packaging
One frozen lamb carcass(PM grade) stored for 6 months at - 18°C and a similar carcassfrozen for lessthan 1week were obtained from a local export 313
314
V. J. Moore
meat works. The loins from each side were cut by bandsaw from the frozen state into twelve 20mm chops, which were packaged in either d-film, an oxygen-permeableshrink film (W. R. Grace, Wellington, oxygen permeability >2000 ml/m2/24 h at 25°C) or in low oxygen permeability tuflex vacuum bags (Trigon Plastics, Hamilton, oxygen permeability = 100ml/m2/24 h at 25°C). Lighting All chops were placed in a General Electric open display caseoperating at -20°C in a room with white walls and ceiling. There was no outside illumination. Three lighting regimes were used: cool white (Thorn, New Zealand), which contains more of the blue end of the spectrum; Deluxe 32” (Phillips, Holland), which has a higher proportion of the red range present; and dark. For dark storage,the chops were held under a light-tight cover, while a hardboard barrier extending to the ceiling separatedchops stored under the two lighting conditions. Four chops wereexposedto eachlighting/ packaging/storage combination. Treatments are outlined in Table 1. Colour measurement Colour was measuredwith a Hunter 25D calorimeter at 0, 1,4,6,8,12,15,18, 22, 27, 36 and 56 days. The measured Hunter L, a, b values were used to evaluate changesin total colour, brightness, hue angle and saturation for each chop, Total colour change measures the change in the three components of colour: lightness (L), red-green (a) and yellow-blue (b). Brightness measures light scattering, or greynessof the meat. Hue angle change measures the change in hue (redness) of the meat. Saturation measuresthe depth of the dominant hue, which in the caseof chops, is red. The formulae used for calculation of the differencebetweenthesefactors at time zero (Hunter values L,, ao, b,) and time x (Hunter values L,, a,, b,) were: Total colour difference= J(Lo - LJ2 + (a0 - a,)’ + (b, - b,)’ Brightness difference= dm Hue angle difference=
tan-’ (a,/b,) - tan-’ (ao/bo)
Saturation difference= Jm
- Jm
Statistical analysis was carried out using a balanced analysis of variance and Duncan’s Multiple Test (Duncan, 1955).
315
Effect of variables on retail display of lamb chops
TABLE 1 Treatment Combinations of Storage, Lighting, and Packaging Film Treatment
Time in frozen storage before packaging and display
1 2 3 4 5 6 I 8 9 10 11 12
6 months 6 months 6 months 6 months 6 months 6 months 1 week 1 week 1 week 1 week 1 week 1 week
Lighting
Packaging film
Cool white Cool white Deluxe 32” Deluxe 32” Dark Dark Cool white Cool white Deluxe 32” Deluxe 32” Dark Dark
O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag
shrink shrink shrink shrink shrink shrink
RESULTS Lighting, packaging, storagetime, and display time all had significant effects on some or all of the parameters examined (Tables 2-5). TABLE 2 Effect of Display Time on Frozen Lamb Chop Colour Differences Displa), time (days)
1 4 6 8 12 I5 18 22 21 36 56 F Probability
Total colour change
Brigh mess change
2.02” 2.11” 2.26”b 2.43”’ 2.48”’ 2.94’ 3.05b’ 3.83’d 3.7l’d 3.71’d 4.26d
0.99” 152”b 1.41”b 1.40”b 1.20nb 1.79bc 1.96” 2.60’ 2.45’ 2.39’ 2.42’
0.001***
o~OOl***
Hue angle change
1.13’ - 1.37”’ - 0.57b’ - 1.02bC - 0.42bC -2.16’ - 0.506’ - 2.80 - 4.47 - 2.75“’ - 4.86” oGI1***
Saturation change
-
0.31” 0.46” 0.72” 0.98” 0.56” 0.99” 1.52” 1.93” 1.68” 2.06” 2.55” 0.079 NS
o*b*r.dValues in the same column with the same superscript letter notation are not significantly different. NS, no significant difference. *** P < 0.001.
316
V. J. Moore TABLE
3
Effect of Carcass Storage Time on Frozen Lamb Chop Colour Difference During Display Storage time
Total colour change
Brightness change
Hue angle change
Saturation change
- 3.43 0.13
- 0.03 1.63
6 months Fresh frozen
2.25 3.21
1.54 1.81
F Probability
0.001***
009 NS
0.001***
OGiI2**
NS, no significant difference. ** P < 0.01 *** P < OQOl.
TABLE
4
Effect of Packaging on Colour Change in Frozen Lamb Chops During Display Packaging film
Total colour change
Brightness change
O,-permeable Vacuum
2.83 1.97
1.38 1.97
F Probability
0.217 NS
o~OOl***
Hue angle change
- 3.69 - 0.39 o~OOl***
Saturation change
- 1.03 0.65 0.45 NS
NS, no significant difference. *** P < OGOl.
TABLE
5
Effect of Lighting on Colour Change in Frozen Lamb Chops During Display Brightness change
Lighting
Total colour change
Cool white Deluxe 32” Dark
3.56 2.62 2.02
2.01h 1.53” 1.50”
F Probability
0001***
0.016*
Hue angle change
Saturation change
- 1.68” - 1.62” - 1.64”
- 2.08* -0.33” -0.12
0.995 NS
0003*
‘** Values in the same column with same letter notation are not significantly different. NS, no significant difference. * P
Effect of variables on retail display of lamb chops
317
Effect of display time Total colour changeincreasedlinearly with increasing time of display. Most of the colour change was in brightness and hue. As display time increased, hue angle initially becamepositive then negative.The brightness effect was linear and indicated that chops were becoming darker in colour. Effect of carcassstorage time Carcassesstored 6 months before cutting and packaging had less overall colour change than those cut from a ‘fresh frozen’ carcass. In carcasses stored for 6 months, the observedcolour changewas largely due to a change in hue with virtually no saturation change, whereas the colour change in carcassesfrozen for 1 week was due to a greater saturation change and no hue change. Effect of packaging Total colour change was of the same magnitude regardlessof packaging film; however,a greaterchangein brightnesswas noted in vacuum packaged chops, and a greater shift in the hue angle with those packaged in oxygenpermeable film. Saturation was unaffected by the type of film. Effect of lighting Both cool white and Deluxe 32” lighting causedgreater total colour change in the chops than was found with those stored in the dark. The greatest change occurred in those under cool white lighting, with greater loss of brightness and saturation of the colour. The differencebetween Deluxe 32” and dark was not significant. Hue anglechangeswere similar with either type of lighting. Table 6 shows the initial and final L, a, b values for the twelve treatment groups as well as the ratio of red to yellow components of colour (a/b). Absolute values of L changedvery little betweeninitial and 56 days’ display. A generaldecreasewas noted in a values,but b values changein an irregular manner. Hunter a and b values were consistently lower in those chops packaged in vacuum bags than in oxygen-permeable film. The a/b ratio decreasedin all treatments of cuts from the carcassstored for 6 months, but when the carcasswas freshly frozen, only the u/b ratio of chops packagedin oxygen-permeable film decreased.
318
V. J. Moore
Hunter
Colour
TABLE 6 Values for Frozen Lamb Chops, Initially
Treatment
1 2 3 4 5 6 I 8 9 10 11 12
L
a
and after 56 days’ Display b
a/b
Initial
Final
Initial
Final
Initial
Find
Initial
Final
24.3 26.1 26.8 25.6 28.1 24.1 29.0 27.0 28.8 25.2 26.7 25.6
25.5 29.1 26.8 29.2 26.4 29.5 28.3 30.4 25.9 24.8 26.5 28.7
11.2 I.9 11.1 8.0 10.8 9.0 13.8 8.1 10.3 I.3 10.3 8.0
1.1 6.4 8.1 4.9 9.2 8.7 8.5 4.7 4.7 6.9 8.0 6.0
5.1 3.9 5.4 3.8 5.6 3.1 7.2 4.9 5.2 3.9 5.5 4.1
5.1 3.8 5.9 3.6 5.9 5.3 5.4 3.8 3.9 2.8 5.2 2.8
1.97 2.04 2.04 2.14 1.93 2.44 1.91 1.64 1.99 1.87 1.86 1.95
1.35 1.66 1.38 1.35 1.56 1.63 1.58 1.23 1.22 2.46 1.55 2.11
DISCUSSION Data from this study indicate that about 8 weeks is the maximum length of time one can hold chops on display at - 20°C. This agrees with the findings of Moore & Duganzich (1985). All treatments examined in this study affected colour retention in some way. Brightness is a measure of light scattering or the greyness component in meat. Lighting, packaging film and display time, but not length of storage of the carcass, affected brightness. Of the three lighting conditions, cool white light had the greatest greying effect on the chops. Chops packaged in vacuum bags greyed more than those in oxygen-permeable film, and length of time on display had an overall linear greying effect on chops. Change in hue angle indicates the degree of change in hue (redness) of the chops. Although lighting caused a greying of chops, probably through moisture loss at the surface, it had little effect on the hue, or predominant colour (red) of the chop. The display time, however, caused a linear decrease in the predominant hue, except that initially the chops became redder (a ‘blooming’ effect which is noticeable even in frozen chops). A significant lighting x packaging interaction (P < 0.001) indicates that although there was a greater loss of redness in chops under cool white or Deluxe 32” light than in the dark, those in vacuum bags actually increased slightly in redness, and the lesser loss of redness in the dark was independent of packaging.
Effect of variables on retail display of lamb chops
319
Chops packaged in oxygen-permeablefilm had a greater loss of their red hue than those packaged in vacuum bags. Although it is usually assumed that very little oxygen crossesan oxygen-permeablefilm at temperatures as low as - 20°C (Lambden et al., 1986),this finding suggeststhat some indeed doescrossthe film barrier to causechangesin the frozen muscle myoglobin. The predominant colour shift was from red towards brown, asillustrated by the a/b ratios shown in Table 6. Chops packaged in oxygen-permeable shrink film (odd-numbered treatments) generally had a greater decreasein a/b ratios. It is interesting, however, that those chops cut from ‘fresh frozen’ carcassand packaged under vacuum exhibited a shift from red towards the blue-red colour of myoglobin, which was not the casewith chops from the carcassstored for 6 months before cutting. Cuts from carcassesthat had been stored for 6 months before cutting showedgreater changein hue,i.e. more browning of the red colour, whereas chops from ‘fresh frozen’ carcasseshad a decreasein both red and yellow colour. This may indicate that ‘fresh frozen’ chops are still very metabolically active whereas those frozen for 6 months are less active. Differencesdue to storagetime in this preliminary study should, however,be acceptedwith caution as they may reflect only carcass variation and not treatment differences. Saturation is an indication of depth of the dominant hue (red).Cool white lighting was associated with a greater decreaseof saturation than either Deluxe 32” or darkness.This correlates well with the change in brightness observed under cool white lights. Chops from ‘fresh frozen’ carcasses exhibited an increasein saturation of the red, whereasthose from 6 month carcassesdid not. Neither packaging film nor display time influenced the saturation of the colour. That packaging film and lighting can effectthe colour of frozen beefis well documented (Kropf, 1980). Very little data are available, however, concerning lighting and packaging effectsin frozen lamb. Hunt et al. (1975) suggestedthat incandescentlighting masked the colour deterioration that was noticeable with cool white lighting. They also found that the use of oxygen-permeablefilm resulted in higher panel scoresof meat colour than film with low oxygen permeability during frozen storage. The effects that are observed when chops are displayed are complex and are influenced by many factors in the display environment. One factor which was not addressedin the present study is temperature of display. Certainly display temperatures above - 18°C adversely affect the colour of chops. Zachariah & Satterlee (1973) showed that the greatest oxidation of myoglobin occurred at temperatures around - 12°C; thus any rise to this temperature would be very deleterious to frozen meat appearance.
320
V. J. Moore
REFERENCES Duncan, D. B. (1955). Biometrics, 11, 1. Hunt, M. C., Smith, R. A., Kropf, D. H. & Tuma, H. T. (1975). .I. Fd. Sci., 40 637. Kropf, D. H. (1980). Recip. Meat ConJ Proc., 33, 15. Lambden, A. E., Chadwick, D. & Gill, C. 0. (1986). J. Fd Technol., 20, 78 1. Moore, V. J. & Duganzich, D. (1985). Proc. N.Z. Sot. An. Prod., 45, 81. Zachariah, N. Y. & Satterlee, L. D. (1973), .I. Fd Sci. 38, 418.
V. J. Moore Meat Industry Research Institute PO Box 617, Hamilton, New Zealand
(Received 28 October 1987; accepted 9 May 1988)
of New Zealand
Inc.,
ResearchNote Effect of Packaging and Display Variables on Retail Display of Frozen Lamb Chops
ABSTRACT Display conditions ofpackaging and lighting and the length offrozen storage of the carcass before cutting were examinedfor their eflect on the colour of frozen chops during display. Lighting eflected a greying and loss of saturation of the colour, while packaging$lm affected brightness and hue angle. Length of storage aflected hue and saturation. Display time afleeted brightness and hue in a linear manner.
INTRODUCTION
For over 100years,New Zealand has marketed lamb overseasin the form of frozen carcasses.In recent years,however, the New Zealand meat industry has started to export frozen consumer cuts, and the performance in the market place of thesecuts has becomeof vital interest.This paper reports on the effectsof carcassstoragetime, packaging film, and lighting conditions on the colour retention of displayed frozen lamb chops. MATERIALS
AND METHODS
Carcass and packaging
One frozen lamb carcass(PM grade) stored for 6 months at - 18°C and a similar carcassfrozen for lessthan 1week were obtained from a local export 313
314
V. J. Moore
meat works. The loins from each side were cut by bandsaw from the frozen state into twelve 20mm chops, which were packaged in either d-film, an oxygen-permeableshrink film (W. R. Grace, Wellington, oxygen permeability >2000 ml/m2/24 h at 25°C) or in low oxygen permeability tuflex vacuum bags (Trigon Plastics, Hamilton, oxygen permeability = 100ml/m2/24 h at 25°C). Lighting All chops were placed in a General Electric open display caseoperating at -20°C in a room with white walls and ceiling. There was no outside illumination. Three lighting regimes were used: cool white (Thorn, New Zealand), which contains more of the blue end of the spectrum; Deluxe 32” (Phillips, Holland), which has a higher proportion of the red range present; and dark. For dark storage,the chops were held under a light-tight cover, while a hardboard barrier extending to the ceiling separatedchops stored under the two lighting conditions. Four chops wereexposedto eachlighting/ packaging/storage combination. Treatments are outlined in Table 1. Colour measurement Colour was measuredwith a Hunter 25D calorimeter at 0, 1,4,6,8,12,15,18, 22, 27, 36 and 56 days. The measured Hunter L, a, b values were used to evaluate changesin total colour, brightness, hue angle and saturation for each chop, Total colour change measures the change in the three components of colour: lightness (L), red-green (a) and yellow-blue (b). Brightness measures light scattering, or greynessof the meat. Hue angle change measures the change in hue (redness) of the meat. Saturation measuresthe depth of the dominant hue, which in the caseof chops, is red. The formulae used for calculation of the differencebetweenthesefactors at time zero (Hunter values L,, ao, b,) and time x (Hunter values L,, a,, b,) were: Total colour difference= J(Lo - LJ2 + (a0 - a,)’ + (b, - b,)’ Brightness difference= dm Hue angle difference=
tan-’ (a,/b,) - tan-’ (ao/bo)
Saturation difference= Jm
- Jm
Statistical analysis was carried out using a balanced analysis of variance and Duncan’s Multiple Test (Duncan, 1955).
315
Effect of variables on retail display of lamb chops
TABLE 1 Treatment Combinations of Storage, Lighting, and Packaging Film Treatment
Time in frozen storage before packaging and display
1 2 3 4 5 6 I 8 9 10 11 12
6 months 6 months 6 months 6 months 6 months 6 months 1 week 1 week 1 week 1 week 1 week 1 week
Lighting
Packaging film
Cool white Cool white Deluxe 32” Deluxe 32” Dark Dark Cool white Cool white Deluxe 32” Deluxe 32” Dark Dark
O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag O,-permeable, Vacuum bag
shrink shrink shrink shrink shrink shrink
RESULTS Lighting, packaging, storagetime, and display time all had significant effects on some or all of the parameters examined (Tables 2-5). TABLE 2 Effect of Display Time on Frozen Lamb Chop Colour Differences Displa), time (days)
1 4 6 8 12 I5 18 22 21 36 56 F Probability
Total colour change
Brigh mess change
2.02” 2.11” 2.26”b 2.43”’ 2.48”’ 2.94’ 3.05b’ 3.83’d 3.7l’d 3.71’d 4.26d
0.99” 152”b 1.41”b 1.40”b 1.20nb 1.79bc 1.96” 2.60’ 2.45’ 2.39’ 2.42’
0.001***
o~OOl***
Hue angle change
1.13’ - 1.37”’ - 0.57b’ - 1.02bC - 0.42bC -2.16’ - 0.506’ - 2.80 - 4.47 - 2.75“’ - 4.86” oGI1***
Saturation change
-
0.31” 0.46” 0.72” 0.98” 0.56” 0.99” 1.52” 1.93” 1.68” 2.06” 2.55” 0.079 NS
o*b*r.dValues in the same column with the same superscript letter notation are not significantly different. NS, no significant difference. *** P < 0.001.
316
V. J. Moore TABLE
3
Effect of Carcass Storage Time on Frozen Lamb Chop Colour Difference During Display Storage time
Total colour change
Brightness change
Hue angle change
Saturation change
- 3.43 0.13
- 0.03 1.63
6 months Fresh frozen
2.25 3.21
1.54 1.81
F Probability
0.001***
009 NS
0.001***
OGiI2**
NS, no significant difference. ** P < 0.01 *** P < OQOl.
TABLE
4
Effect of Packaging on Colour Change in Frozen Lamb Chops During Display Packaging film
Total colour change
Brightness change
O,-permeable Vacuum
2.83 1.97
1.38 1.97
F Probability
0.217 NS
o~OOl***
Hue angle change
- 3.69 - 0.39 o~OOl***
Saturation change
- 1.03 0.65 0.45 NS
NS, no significant difference. *** P < OGOl.
TABLE
5
Effect of Lighting on Colour Change in Frozen Lamb Chops During Display Brightness change
Lighting
Total colour change
Cool white Deluxe 32” Dark
3.56 2.62 2.02
2.01h 1.53” 1.50”
F Probability
0001***
0.016*
Hue angle change
Saturation change
- 1.68” - 1.62” - 1.64”
- 2.08* -0.33” -0.12
0.995 NS
0003*
‘** Values in the same column with same letter notation are not significantly different. NS, no significant difference. * P
Effect of variables on retail display of lamb chops
317
Effect of display time Total colour changeincreasedlinearly with increasing time of display. Most of the colour change was in brightness and hue. As display time increased, hue angle initially becamepositive then negative.The brightness effect was linear and indicated that chops were becoming darker in colour. Effect of carcassstorage time Carcassesstored 6 months before cutting and packaging had less overall colour change than those cut from a ‘fresh frozen’ carcass. In carcasses stored for 6 months, the observedcolour changewas largely due to a change in hue with virtually no saturation change, whereas the colour change in carcassesfrozen for 1 week was due to a greater saturation change and no hue change. Effect of packaging Total colour change was of the same magnitude regardlessof packaging film; however,a greaterchangein brightnesswas noted in vacuum packaged chops, and a greater shift in the hue angle with those packaged in oxygenpermeable film. Saturation was unaffected by the type of film. Effect of lighting Both cool white and Deluxe 32” lighting causedgreater total colour change in the chops than was found with those stored in the dark. The greatest change occurred in those under cool white lighting, with greater loss of brightness and saturation of the colour. The differencebetween Deluxe 32” and dark was not significant. Hue anglechangeswere similar with either type of lighting. Table 6 shows the initial and final L, a, b values for the twelve treatment groups as well as the ratio of red to yellow components of colour (a/b). Absolute values of L changedvery little betweeninitial and 56 days’ display. A generaldecreasewas noted in a values,but b values changein an irregular manner. Hunter a and b values were consistently lower in those chops packaged in vacuum bags than in oxygen-permeable film. The a/b ratio decreasedin all treatments of cuts from the carcassstored for 6 months, but when the carcasswas freshly frozen, only the u/b ratio of chops packagedin oxygen-permeable film decreased.
318
V. J. Moore
Hunter
Colour
TABLE 6 Values for Frozen Lamb Chops, Initially
Treatment
1 2 3 4 5 6 I 8 9 10 11 12
L
a
and after 56 days’ Display b
a/b
Initial
Final
Initial
Final
Initial
Find
Initial
Final
24.3 26.1 26.8 25.6 28.1 24.1 29.0 27.0 28.8 25.2 26.7 25.6
25.5 29.1 26.8 29.2 26.4 29.5 28.3 30.4 25.9 24.8 26.5 28.7
11.2 I.9 11.1 8.0 10.8 9.0 13.8 8.1 10.3 I.3 10.3 8.0
1.1 6.4 8.1 4.9 9.2 8.7 8.5 4.7 4.7 6.9 8.0 6.0
5.1 3.9 5.4 3.8 5.6 3.1 7.2 4.9 5.2 3.9 5.5 4.1
5.1 3.8 5.9 3.6 5.9 5.3 5.4 3.8 3.9 2.8 5.2 2.8
1.97 2.04 2.04 2.14 1.93 2.44 1.91 1.64 1.99 1.87 1.86 1.95
1.35 1.66 1.38 1.35 1.56 1.63 1.58 1.23 1.22 2.46 1.55 2.11
DISCUSSION Data from this study indicate that about 8 weeks is the maximum length of time one can hold chops on display at - 20°C. This agrees with the findings of Moore & Duganzich (1985). All treatments examined in this study affected colour retention in some way. Brightness is a measure of light scattering or the greyness component in meat. Lighting, packaging film and display time, but not length of storage of the carcass, affected brightness. Of the three lighting conditions, cool white light had the greatest greying effect on the chops. Chops packaged in vacuum bags greyed more than those in oxygen-permeable film, and length of time on display had an overall linear greying effect on chops. Change in hue angle indicates the degree of change in hue (redness) of the chops. Although lighting caused a greying of chops, probably through moisture loss at the surface, it had little effect on the hue, or predominant colour (red) of the chop. The display time, however, caused a linear decrease in the predominant hue, except that initially the chops became redder (a ‘blooming’ effect which is noticeable even in frozen chops). A significant lighting x packaging interaction (P < 0.001) indicates that although there was a greater loss of redness in chops under cool white or Deluxe 32” light than in the dark, those in vacuum bags actually increased slightly in redness, and the lesser loss of redness in the dark was independent of packaging.
Effect of variables on retail display of lamb chops
319
Chops packaged in oxygen-permeablefilm had a greater loss of their red hue than those packaged in vacuum bags. Although it is usually assumed that very little oxygen crossesan oxygen-permeablefilm at temperatures as low as - 20°C (Lambden et al., 1986),this finding suggeststhat some indeed doescrossthe film barrier to causechangesin the frozen muscle myoglobin. The predominant colour shift was from red towards brown, asillustrated by the a/b ratios shown in Table 6. Chops packaged in oxygen-permeable shrink film (odd-numbered treatments) generally had a greater decreasein a/b ratios. It is interesting, however, that those chops cut from ‘fresh frozen’ carcassand packaged under vacuum exhibited a shift from red towards the blue-red colour of myoglobin, which was not the casewith chops from the carcassstored for 6 months before cutting. Cuts from carcassesthat had been stored for 6 months before cutting showedgreater changein hue,i.e. more browning of the red colour, whereas chops from ‘fresh frozen’ carcasseshad a decreasein both red and yellow colour. This may indicate that ‘fresh frozen’ chops are still very metabolically active whereas those frozen for 6 months are less active. Differencesdue to storagetime in this preliminary study should, however,be acceptedwith caution as they may reflect only carcass variation and not treatment differences. Saturation is an indication of depth of the dominant hue (red).Cool white lighting was associated with a greater decreaseof saturation than either Deluxe 32” or darkness.This correlates well with the change in brightness observed under cool white lights. Chops from ‘fresh frozen’ carcasses exhibited an increasein saturation of the red, whereasthose from 6 month carcassesdid not. Neither packaging film nor display time influenced the saturation of the colour. That packaging film and lighting can effectthe colour of frozen beefis well documented (Kropf, 1980). Very little data are available, however, concerning lighting and packaging effectsin frozen lamb. Hunt et al. (1975) suggestedthat incandescentlighting masked the colour deterioration that was noticeable with cool white lighting. They also found that the use of oxygen-permeablefilm resulted in higher panel scoresof meat colour than film with low oxygen permeability during frozen storage. The effects that are observed when chops are displayed are complex and are influenced by many factors in the display environment. One factor which was not addressedin the present study is temperature of display. Certainly display temperatures above - 18°C adversely affect the colour of chops. Zachariah & Satterlee (1973) showed that the greatest oxidation of myoglobin occurred at temperatures around - 12°C; thus any rise to this temperature would be very deleterious to frozen meat appearance.
320
V. J. Moore
REFERENCES Duncan, D. B. (1955). Biometrics, 11, 1. Hunt, M. C., Smith, R. A., Kropf, D. H. & Tuma, H. T. (1975). .I. Fd. Sci., 40 637. Kropf, D. H. (1980). Recip. Meat ConJ Proc., 33, 15. Lambden, A. E., Chadwick, D. & Gill, C. 0. (1986). J. Fd Technol., 20, 78 1. Moore, V. J. & Duganzich, D. (1985). Proc. N.Z. Sot. An. Prod., 45, 81. Zachariah, N. Y. & Satterlee, L. D. (1973), .I. Fd Sci. 38, 418.
V. J. Moore Meat Industry Research Institute PO Box 617, Hamilton, New Zealand
(Received 28 October 1987; accepted 9 May 1988)
of New Zealand
Inc.,