Ebook Guide To Canning And Preserving
The commercial canning process uses pressurized steam in an industrial-sized autoclave called a retort. Conditions of the process are designed to ensure that endospores of Clostridium botulinum are destroyed. This is critical because surviving spores can germinate and the resulting vegetative cells can grow in the anaerobic conditions of low-acid canned foods, such as vegetables and meats, and produce botulinum toxin, one of the most potent toxins known. Because ingestion of even minute amounts of botulinum toxin can be lethal, the canning process of low-acid foods is designed to kill all endospores of C. botulinum. In doing so, the process also kills all other organisms capable of growing under normal storage conditions. Endospores of some thermophilic bacteria may survive the canning process, but these are usually of no concern because they only can grow at temperatures well above those of normal storage. Because of this, canned foods are called commercially sterile to reflect the...
There are varying opinions about the interpretation of the sexual processes (Canning 1988 Flegel and Pasharawipas 1995). Most reports of sexuality in microsporidia are not based on observed zygote production but on the presence of synaptonemal complexes (coupled chromosomes in the reductional division) visible in ultrathin sections of sporonts (Larsson 1986).
In the infected tissue cell walls might be destroyed, transforming the tissue into a syncytium where the developmental stages of the microsporidium are floating among host nuclei. Microsporidia of fish sometimes induce the production of tumours. The best known example is the xenoma caused by Glugea anomala, a common skin parasite of sticklebacks. The microsporidium completely rules the infected epidermis cell, inducing nuclear fission, cell hypertrophy, and encapsulation processes (Canning et al. 1982). The final xenoma is a rounded body, a few millimetres in diameter, which contains hundreds, or even thousands, of host nuclei and millions of microsporidia. It is encapsulated by numerous layers of fibroblasts and material from the host cell surface coat.
The new genus Vittaforma was established by Silveira and Canning (1995) for a species previously known as Nosema corneum. It was originally isolated from the cornea of an immunocompetent patient. Trachipleistophora hominis, described by Hollister et al. (1996), was originally found in skeletal muscles of AIDS patients, but has later also been observed in cornea scrapings and washings from the nasopharyngeal tract. A second species, T. anthropophthera, was recently found in brain, kidneys, liver, and a variety of other organs in an AIDS patient (Vavra et al. 1998). This is a dimorphic species,
The canning industry has enjoyed an enviable record of safety, and thus the concept of logarithmic death of microorganisms has persisted, and is now considered accepted dogma. In spite of this, nonlinear survival curves were reported for some bacteria almost 100 years ago.83 In general there are two classes of nonlinear curves those with a shoulder or lag prior to inactivation, and those that exhibit tailing. These two phenomena may be present together, or with other observed kinetics such as biphasic inactivation. A wide variety of complex inactivation kinetics have been reported, and several of these are shown in Figure 2.6. The theoretical basis for assuming logarithmic behavior for bacteria is based on the assumptions that bacterial populations are homogeneous with respect to thermal tolerance, and that inactivation is due to a single critical site per cell.83 Both of these assumptions have been questioned, and thus concerns have been raised regarding the validity of extrapolation...
Thermal inactivation of microorganisms in static or batch systems is usually described by the D- and z-value concepts as discussed above, with temperature generally held constant. The situation in canning operations or continuous flow systems such as HTST pasteurization, sterilization, and ultrahigh temperature processes is somewhat more complex, due to nonisothermal conditions. In addition, the kinetics of inactivation in continuous systems differs from that in batch systems since in these systems there are additional factors such as pressure and shear forces that can influence microbial survival.131 As most modern processes are continuous, it is necessary to have information on survival of microorganisms however, few studies have been published in which laboratory or pilot plant continuous flow systems have been studied.131
Prevention of botulism depends on proper sterilization and sealing of food at the time of canning. Fortunately, the toxin is heat-labile, and heating food to 100 C for 15 minutes just prior to serving generally makes it safe to eat. One cannot rely on a spoiled smell, taste, or appearance to detect contamination, because such changes are not always present. The disease is treated by the intravenous administration of antitoxin as soon as possible after the diagnosis is made. The antitoxin, however, only neutralizes toxin circulating in the bloodstream, and the nerves already affected by it recover slowly, over weeks or months. Enemas, gastric washing, and surgical removal of dirt and dead tissue from infected wounds help remove any unabsorbed toxin. Artificial respiration may be required for prolonged periods.
In the commercial canning industry, the D value, or decimal reduction time, is defined as the time it takes to kill 90 of a population of bacteria under specific conditions. (Figure 5.2) 4. The most important aspect of the commercial canning process is to ensure that endospores of Clostridium botulinum are destroyed. (Figure 5.5)
If there are any fruits that have always given you indigestion in the past, try eating them first thing in the morning when your stomach is typically completely empty. Chew very well. You may be surprised at how well your body receives this meal. Many diets advise the limitation of fruit to one or two small portions a day. If you follow the rule to always eat fruit on an empty stomach, you may find that there needn't be such a limitation on fruit intake, unless you eat so much fruit that other important foods end up excluded due to a lack of hunger or appetite. Fruits are wonderful foods, and should not be minimized by nutritional counselors unaware of the manner required by fruit to be properly digested. Also, fruits should only be eaten raw, which further promotes digestion, since the natural enzyme content in the fruit hasn't been destroyed or severely limited by the cooking process, preserving process, or canning packaging process. Processed fruits, especially those with added...
Modeling the inactivation of bacterial spores presents a unique problem. Spore-forming bacteria such as Bacillus and Clostridium spp. can exist in a dormant (spore) stage that is highly heat resistant. Germination of spores can be achieved by treatment with sublethal heat.123 Because of the extreme heat resistance of some of these microorganisms, activated spore preparations have traditionally been used to establish sterilization protocols in the canning and ultrahigh temperature industries.124 As described earlier, the classical view of microbial thermal inactivation ascribes a first-order reaction to the process however, it has been difficult to consistently achieve simple exponential inactivation with spore preparations. These variations manifest themselves as a shoulder on the decay curve, which has been attributed to activation of spores, and subsequent differences in the heat resistance of dormant and activated spores.125 Consistent populations of activated spores are difficult...
Autumn draws near, and with the coming of cold weather summer's fruits will soon vanish. How can they best be preserved to last through the winter Several methods are common, especially canning and freezing. In each case one seeks to prevent the proliferation of germs, which at room temperature occurs rapidly in foods that contain sufficient quantities of water and organic matter to favor the development of microorganisms.
Moist heat such as boiling water destroys vegetative bacteria and viruses. Pasteurization significantly reduces the numbers of heat-sensitive organisms. Autoclaves use pressurized steam to achieve high temperatures that kill microbes, including endospores. The commercial canning process is designed to destroy the endospores of Clostridium botulinum. Dry heat takes longer than moist heat to kill microbes. Why is it important that the commercial canning process destroys the endospores of Clostridium botulinum
Botulism is a paralytic disease caused by ingestion of a neurotoxin produced by the anaerobic, spore-forming, Gram-positive rod Clostridium botulinum. Unfortunately, growth of the organism and production of the deadly toxin may not result in any noticeable changes in the taste or appearance of the food. Canning processes are specifically designed to destroy the endospores of this organism, but processing errors or postprocessing contamination can allow the germination of the endospores and growth of the vegetative cells that produce toxin.