English to Spanish Tech/Engineering Chemistry; Chem Sci/Eng heat penetration in packaged food

The simplest form of this is to use a capillary tube filled with the inoculum. Alternatively, small bulbs of approximately 5 mm outside diameter that hold 0.05 ml can be used. These are filled by means of an accurate syringe. The advantage of using bulbs is that they can be located at the point of slowest heating or in particles of food or synthetic material. The time required for the bulb and contents to reach the temperature of the surroundings, up to 121.1°C, is about 15 s, and the contribution of the come-up time to the total process time is about 6 s at the operating temperature – thus 9 s is subtracted from the contact time to give the time of exposure (Hersom & Hulland 1980). The bulbs may be located at the appropriate point in the can by using a Tufnol rod 6 mm wide and 3 mm deep, cut to an appropriate length to fit the can diagonally from top to bottom. The stem of the capillary is inserted through a small hole in the rod and the bulb secured by a short collar of silicon elastomer. Each bulb contains approximately. spores of, for example, the highly heat resistant Bacillus stearothermophilus suspended in citrate buffer. The process lethality can then be determined from the initial number of spores and the number of survivors. The heat resistance can be obtained by using replicate bulbs, processed under the same conditions.