Why to stop climate change? Importance of Food Safety.
Jyrki Turunen
M. Sc. Thesis Department of Food technology
November 2004
Viikki Science Library
EKT-series 1328
Abstract
The significance of the cold chain and quality attributes of raw milk were reviewed. The objectives of the experimental research were to follow the temperature of raw milk during delivery from farm to dairy plant and subsequent quality attributes. The applicability of liquid nitrogen to maintain raw milk temperature ang significance of cooling the milk tanker with liquid nitrogen before colllection was also tested. In addition the effect of modified atmosphere in milk tanker to bacterial growth in raw milk was examined.
The experimental research was carried out between 4th April and 10th June 2004. There were five separated test periods. During first three periods, A, B and C, farm milks were collected by truck and trailer. In later periods D and E milks were only by truck. During period B two of the trailer containers were cooled by liquid nitrogen. Total bacterial count, psychrotrops, aerobic spores and FFA (free faatty acids) of the raw milk loads were tested. Total bacterial count and FFA of farm milks were tested. The temperature of the milk was measured both load and farm milks.
During periods A,B and C air temperatures outsides were in order +9˚C, +14˚C and +22˚C respectively. The temperature of the raw milk rose 70% faster during period C than during period A and 55% faster than at period B. There was no difference between farm milk temperatures between the periods. Total bacterial counts were highest in period C and lowest in period A,, it was same for both farm and truckload milks. There was no effect on the final-temperatute of the truckload if the containers were pre-cooled. But it seems to be possible that nitrogen modified atmosphere in milk tanker had an effect of extending the bacterial lag-phase. Raw milk is also possible to be cooled by liquid nitrogen.
tiistai 19. tammikuuta 2010
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