Abstract
The membrane filtration technique as applied in multiplant brewery quality control has been unsatisfactory because of dehydration and subsequent death of entrapped microbes during shipment (storage) of membranes. Gram-negative bacteria and lager yeast were shown to be very susceptible to such storage over five days at humidities ranging from 0 to 98%. Gram-positive brewing bacteria, however, were much more resistant over the whole range of humidity. A number of compounds were used as protective agents in an attempt to prevent dehydration and subsequent death. One of them, 4% reconstituted skim milk powder, was extremely effective in reduction of death and is now recommended as a protective washing solution for microbes collected on membranes. Use of this protective agent allows membranes to be shipped by mail in sterile Whirlpak bags under a variety of conditions with no appreciable microbial die-off.