Antimicrobial activity of cinnamon and clove oils under modified atmosphere conditions.

Mixtures of cinnamon and clove oils were tested for inhibitory activity against important spoilage microorganism of intermediate moisture foods. Four fungal species (Aspergillus flavus, Penicillium roqueforti, Mucor plumbeus and Eurotium sp.), four yeasts species (Debaryomyces hansenii, Pichia membranaefaciens, Zygosaccharomyces rouxii and Candida lipolytica), and two bacteria species (Staphylococcus aureus and Pediococcus halophilus) inoculated separately on agar plates were sealed in a barrier pouch and exposed to essential oil volatiles under a modified atmosphere of low O2 (<0.05-10%) and high CO2 (20% or 40%), with the balance being N2. A. flavus and Eurotium sp. proved to be the most resistant microorganisms. Cinnamon and clove oils added between 1000 and 4000 microL at a ratio of 1:1 were tested for minimum inhibitory volume (MIV) against molds and yeasts. The gas phase above 1000 microL of the oil mixture inhibited growth of C. lipolytica and P. membranaefaciens; 2000 microL inhibited growth of A. flavus, P. roqueforti, M. plumbeus, Eurotium sp., D. hansenii, and Z. rouxii, while inhibition of A. flavus required the addition of 4000 microL. Higher ratios of cinnamon oil/clove oil were more effective for inhibiting the growth of A. flavus.

Membrane cleaning in the dairy industry: a review.

Membrane separation processes have become part of the set of basic unit operations for dairy process design and product development. These processes are employed in a variety of separation and concentration duties, but in all cases, the membranes must be cleaned regularly to remove both organic and inorganic material deposited on the surface from the fluid stream being processed. Cleaning is a vital step in maintaining the permeability and selectivity of the membrane and is necessary to return the plant to its original capacity, to minimize risks of bacteriological contamination, and to produce acceptable products. Caustic-, acidic-, and enzyme-based cleaners may be used for membrane cleaning and are usually formulated with additives to best match the specific cleaning duty. Cleaning generates significant volumes of wastewater and reduces membrane life and plant productivity, so each regime must be optimized with respect to concentration, order and duration of cleaning steps, temperature, pressure, and flow rate. This article reviews the key mechanisms governing cleaning performance and suggests directions by which further optimization may be achieved.

Crossflow microfiltration of cell suspensions.

The application of crossflow microfiltration (CFMF) to processing cell suspensions was proposed in the 1970s. The intervening years have seen the scaling up of the technology to commercial operation and have been a period of intense research interest in the physics of the process. Flaschel et al. (1983) noted that the recovery of biomass (by ultrafiltration) appeared still to be in the phase of development. Later reviews particularly commented on the proprietary nature of much of the useful information required to assess the feasibility of CFMF (Hanisch, 1986; Brown & Kavanagh, 1987), but while the need for further publication of some information is still being stressed (e.g. Heath and Belfort, 1992), detailed reports from biotechnology companies of lab-, pilot- and full-scale applications are now appearing in the literature (Bailey et al., 1990, Sheehan et al, 1990; van Reis et al., 1991). The objective of this review is to describe the major factors influencing CFMF of cell suspensions with particular reference to the recent literature.