Effect of short- and long-term frozen storage with MAP on the quality of freeze-chilled lasagne

The effect of long- and short-term frozen storage prior to thawing, on the quality of freeze-chilled, commercially made lasagnes was examined as was the effect of modified atmosphere packaging (MAP). In the short-term trial, four process treatments were used; fresh, chilled, freeze-chilled and frozen. In the long-term trial, the lasagnes were frozen for 3, 6, 9 or 12 months, thawed and tested, or were thawed and then chilled at 4°C for 6 days (freeze-chilled). In the MAP trial, the lasagnes were subjected to either the freeze-chill treatment or freeze treatment, and before freezing were packed in either (i) air, (ii) 40% CO2/60% N2 or (iii) 40% CO2/30% N2/30% O2. In the short-term trial frozen and freeze-chilled lasagne had significantly higher drip loss than fresh or chilled before reheating, but this was not evident after heating. Similarly, freeze-chilled lasagne had a brighter colour (L/b) than chilled before heating, but again this was not evident after heating. No difference was found in firmness or sensory acceptability of lasagne from the different treatments. Freeze-chilled and frozen lasagne had higher total viable counts (TVC) than chilled or fresh. Packing in CO2/N2/O2 (40:30:30) led to a darker unheated lasagne than packing in CO2/N2 (40:60) or air, but this was not evident for heated lasagne. Packing in CO2/N2 (40:60) led to a firmer product than packing in air for the frozen lasagne but not for freeze-chilled lasagne. Atmosphere had no effect on TVC or drip loss values. Lasagnes stored frozen for 12 months were firmer than those stored for 3, 6, or 9 months. Storing frozen for 9 or 12 months also led to higher drip loss values than storing for 3 months for unheated lasagnes but when heated, the opposite effect was seen. Lasagnes stored for 3 months had the highest L/b (white/yellow ratio) values while those stored for 12 months had the lowest. Length of time in frozen storage had no influence on TVC values.