A method using a combination of ball milling, acid hydrolysis, and ultrasound was developed to obtain a high yield of cellulose nanofibers from flax fibers and microcrystalline cellulose (MCC). Poly(vinyl alcohol) (PVA) nanocomposites were prepared with these additives by a solution-casting technique. The cellulose nanofibers and nanocomposite films that were produced were characterized with Fourier transform infrared spectrometry, Xray diffraction, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Nanofibers derived from MCC were on average approximately 8 nm in diameter and 111 nm in length. The diameter of the cellulose nanofibers produced from flax fibers was approximately 9 nm, and the length was 141 nm. A significant enhancement of the thermal and mechanical properties was achieved with a small addition of cellulose nanofibers to the polymer matrix. Interestingly, the flax nanofibers had the same reinforcing effects as MCC nanofibers in the matrix. Dynamic mechanical analysis results indicated that the use of cellulose nanofibers (acid hydrolysis) induced a mechanical percolation phenomenon leading to outstanding and unusual mechanical properties through the formation of a rigid filler network in the PVA matrix. X-ray diffraction showed that there was no significant change in the crystallinity of the PVA matrix with the incorporation of cellulose nanofibers.

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Summary Aims:  The aim of this work was to investigate the germination and inactivation of spores of Bacillus species in buffer and milk subjected to high pressure (HP) and nisin. Methods and Results:  Spores of Bacillus subtilis and Bacillus cereus suspended in milk or buffer were treated at 100 or 500 MPa at 40°C with or without 500 IU ml−1 of nisin. Treatment at 500 MPa resulted in high levels of germination (4 log units) of B. subtilis spores in both milk and buffer; this increased to >6 logs by applying a second cycle of pressure. Viability of B. subtilis spores in milk and buffer was reduced by 2·5 logs by cycled HP, while the addition of nisin (500 IU ml−1) prior to HP treatment resulted in log reductions of 5·7 and 5·9 in phosphate buffered saline and milk, respectively. Physical damage of spores of B. subtilis following HP was apparent using scanning electron microscopy. Treating four strains of B. cereus at 500 MPa for 5 min twice at 40°C in the presence of 500 IU ml−1 nisin proved less effective at inactivating the spores of these isolates compared with B. subtilis and some strain‐to‐strain variability was observed. Conclusions:  Although high levels of germination of Bacillus spores could be achieved by combining HP and nisin, complete inactivation was not achieved using the aforementioned treatments. Significance and Impact of the Study:  Combinations of HP treatment and nisin may be an appealing alternative to heat pasteurization of milk.

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Ethanol dehydration followed by argon replacement induced drying (ARID) was found to be a suitable method for the preparation of glass, stainless steel and rubber surfaces which had been in contact with inoculated milk and which were to be examined using scanning electron microscopy (SEM). This technique was used to examine samples of all three materials which had been subjected to both single and repeated inoculation with whole milk containing a Pseudomonas sp. or a Micrococcus sp. and incubated for various periods. Some samples were also prepared for SEM using a cryofixation technique. The Pseudomonas sp. was found to proliferate on glass and stainless steel surfaces but not on rubber. Due to the clumping tendency of the Micrococcus sp. proliferation of this organism was more difficult to assess accurately. In general there was no difference in results obtained between single and repeated inoculation. Various factors which may have aided attachment of micro-organisms to surfaces were identified viz., surface channels present in stainless steel, milk deposits and the production of extracellular material. The value of using both the cryofixation and chemical preparatory techniques for the identification of artifacts is discussed.