The effect of chitosan in meat preservation, including microbiological, chemical, sensory and color qualities, was examined. In liquid medium, chitosan (0·01%) inhibited the growth of some spoilage bacteria such as Bacillus subtilis IFO 3025, Escherichia coli RB, Pseudomonas fragi IFO 3458 and Staphylococcus aureus IAM 1011. At higher concentrations (0·1 and 1·0%) it inhibited the growth of the meat starter cultures, Lactobacillus plantarium IAM 1216, Pediococcus pentosaceus IAM 12296 and Micrococcus varians IFO 3765. In meat, during incubation at 30°C for 48 h or storage at 4°C for 10 days, 0·5-1·0% chitosan inhibited the growth of spoilage bacteria, reduced lipid oxidation and putrefaction, and resulted in better sensory attributes. Chitosan also had a good effect on the development of the red color of meat during storage.

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Rat soleus muscle Z-lines and Z-line anomalies induced by neostigmine methyl sulfate (NMS) and cat soleus muscle Z-lines and Z-line anomalies induced by tenotomy were examined by electron microscopy before and after dissection of muscle fibers with Ca2+-activated neutral protease (CAF) to elucidate structural properties of Z-lines and related Z-line-type structures. In both normal and treated muscles, interdigitation of thin (6-7 nm) filaments, which were continuous with I-filaments (actin) from adjacent sarcomeres, was observed at the Z-line in longitudinal section. Both neostigmine methyl sulfate and tenotomy treatments induced muscle atrophy associated with Z-line degradation, streaming, and irregular distribution and accumulation of Z-line material and Z-rod formation. Tenotomized muscle also was characterized by the presence of N-line-like bands and I-Z-I brushes. CAF digestion removed the electron-dense covering material from Z-rods and revealed a backbone of actin filaments. The origin of Z-rods, their structural similarity to Z-lines in longitudinal and cross section, and their susceptibility to CAF indicate that Z-rods are directly related to native Z-lines and are probably lateral polymers of a basic Z-line unit. The regular square net alignment (22 nm) of I-filaments (actin) in cross sections of I-Z-I brushes which contain no N-lines suggests that the I-square net arrangement near the Z-line is determined by Z-filament-actin filament interaction rather than by the N-line or other factors. The results suggest that I-filaments (actin) penetrate the mammalian Z-line and are Z-line constituents and that the width of Z-lines and the length of Z-rods are determined by the amount of overlap of actin filaments. The perpendicular periodicity of Z-rods and the zigzag-oblique arrowheadlike appearance seen in longitudinal sections of Z-lines are attributed to alpha-actinin.