2. Materials and methods
2.1. Rawmaterials and sample preparation
To determine the effect of rate of freezing on protein
functionality, m. semitendinosus muscles from 12 heifers
were hot-boned and held at 10 C until rigor. Each
muscle was divided into two equal portions (referred to
as front and back, each 170 mm long 110 mm diameter).
A Latin Square design to account for positional
effects was used to allocate the 48 portions to four
freezing treatments: (1) Slow blast-freeze (1.8 mm/h):
samples at 10 C were each vacuum packed, wrapped in
a single layer of 10 mm thick foam rubber and placed in
front of the fans in a20 C freezer until the temperature
reached 20 C, measured with a T-type thermocouple
inserted in the middle of the sample. (2) Fast
blast-freeze (7.8 mm/h): samples were frozen as in slow
blast, except that the samples were not insulated with
foam rubber, thus producing a faster freezing rate. (3)
Fast liquid nitrogen (49.8 mm/h; two treatments): samples
at 10 C were vacuum packed and frozen in a batch
liquid nitrogen freezer or samples were vacuum packed
and slow chilled from 10 C to 0 C, then frozen in a
batch liquid nitrogen freezer to 20 C. The batch liquid
nitrogen freezer was operating at a temperature of 80 C.
The air temperature in the batch freezer was controlled by
periodically spraying liquid nitrogen into the freezer—no
liquid nitrogen was directly sprayed onto samples.
The samples
2. Materials and methods2.1. Rawmaterials and sample preparationTo determine the effect of rate of freezing on proteinfunctionality, m. semitendinosus muscles from 12 heiferswere hot-boned and held at 10 C until rigor. Eachmuscle was divided into two equal portions (referred toas front and back, each 170 mm long 110 mm diameter).A Latin Square design to account for positionaleffects was used to allocate the 48 portions to fourfreezing treatments: (1) Slow blast-freeze (1.8 mm/h):samples at 10 C were each vacuum packed, wrapped ina single layer of 10 mm thick foam rubber and placed infront of the fans in a20 C freezer until the temperaturereached 20 C, measured with a T-type thermocoupleinserted in the middle of the sample. (2) Fastblast-freeze (7.8 mm/h): samples were frozen as in slowblast, except that the samples were not insulated withfoam rubber, thus producing a faster freezing rate. (3)Fast liquid nitrogen (49.8 mm/h; two treatments): samplesat 10 C were vacuum packed and frozen in a batchliquid nitrogen freezer or samples were vacuum packedand slow chilled from 10 C to 0 C, then frozen in abatch liquid nitrogen freezer to 20 C. The batch liquidnitrogen freezer was operating at a temperature of 80 C.The air temperature in the batch freezer was controlled byperiodically spraying liquid nitrogen into the freezer—noliquid nitrogen was directly sprayed onto samples.The samples
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