A literature review is presented regarding the synthesis, and physicochemical, chemical, and mechanical properties of poly(lactic acid)(PLA). Poly(lactic acid) exists as a polymeric helix, with an orthorhombic unit cell. The tensile properties of PLA can vary widely, depending on whether or not it is annealed or oriented or what its degree of crystallinity is. Also discussed are the effects of processing on PLA. Crystallization and crystallization kinetics of PLA are also investigated. Solution and melt rheology of PLA is also discussed. Four different power-law equations and 14 different Mark–Houwink equations are presented for PLA. Nuclear magnetic resonance, UV–VIS, and FTIR spectroscopy of PLA are briefly discussed. Finally, research conducted on starch–PLA composites is introduced.

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A Literature Review of Poly(Lactic Acid)

Processing technologies for poly(lactic acid)

It has become increasingly clear that life-history patterns among the vertebrates have been shaped by the plethora and variety of immunological risks associated with parasitic faunas in their environments. Immunological competence could very well be the most important determinant of life-time reproductive success and fitness for many species. It is generally assumed by evolutionary ecologists that providing immunological defences to minimise such risks to the host is costly in terms of necessitating trade-offs with other nutrient-demanding processes such as growth, reproduction, and thermoregulation. Studies devoted to providing assessments of such costs and how they may force evolutionary trade-offs among life-history characters are few, especially for wild vertebrate species, and their results are widely scattered throughout the literature. In this paper we attempt to review this literature to obtain a better understanding of energetic and nutritional costs for maintaining a normal immune system and examine how costly it might be for a host who is forced to up-regulate its immunological defence mechanisms. The significance of these various costs to ecology and life history trade-offs among the vertebrates is explored. It is concluded that sufficient evidence exists to support the primary assumption that immunological defences are costly to the vertebrate host.

https://www.jstor.org/stable/pdfplus/3546398.pdf

Trade‐offs in evolutionary immunology: just what is the cost of immunity?

For a long time polymers have supplied most of common packaging materials because they present several desired features like softness, lightness and transparency. However, increased use of synthetic packaging films has led to a serious ecological problems due to their total non-biodegradability. Although their complete replacement with eco-friendly packaging films is just impossible to achieve, at least for specific applications like food packaging the use of bioplastics should be the future. The aim of this review was to offer a complete view of the state of the art on biodegradable polymer packages for food application.

Biodegradable polymers for food packaging: a review

Research and development of antimicrobial materials for food applications such as packaging and other food contact surfaces is expected to grow in the next decade with the advent of new polymer materials and antimicrobials. This article reviews the different types of antimicrobial polymers developed for food contact, commercial applications, testing methods, regulations and future trends. Special emphasis will be on the advantages/disadvantages of each technology.

Review of antimicrobial food packaging

Dietary sources of conjugated dienoic isomers of linoleic acid, a newly recognized class of anticarcinogens

The effects of conjugated linoleic acid (CLA) on body composition were investigated. ICR mice were fed a control diet containing 5.5% corn oil or a CLA-supplemented diet (5.0% corn oil plus 0.5% CLA). Mice fed CLA-supplemented diet exhibited 57% and 60% lower body fat and 5% and 14% increased lean body mass relative to controls (P < 0.05). Total carnitine palmitoyltransferase activity was increased by dietary CLA supplementation in both fat pad and skeletal muscle; the differences were significant for fat pad of fed mice and skeletal muscle of fasted mice. In cultured 3T3-L1 adipocytes CLA treatment (1 x 10(-4)M) significantly reduced heparin-releasable lipoprotein lipase activity (-66%) and the intracellular concentrations of triacylglyceride (-8%) and glycerol (-15%), but significantly increased free glycerol in the culture medium (+22%) compared to control (P < 0.05). The effects of CLA on body composition appear to be due in part to reduced fat deposition and increased lipolysis in adipocytes, possibly coupled with enhanced fatty acid oxidation in both muscle cells and adipocytes.

Effect of conjugated linoleic acid on body composition in mice

The Biologically Active Isomers of Conjugated Linoleic Acid

Conjugated linoleic acid and atherosclerosis in rabbits

Fried ground beef contains substances that inhibit mutagenesis in bacteria and the initiation of epidermal carcinogenesis in mice by 7,12-dimethylbenz [a]anthracene (DMBA). The inhibitors apparently act at least in part via inhibition of cytochrome P-450 activity. A highly purified fraction that inhibited cytochrome P-450 activity in vitro was isolated by HPLC and characterized by GC-MS, and by UV and proton NMR spectroscopy. The fraction contained four isomeric derivatives of linoleic acid each containing a conjugated double-bond system (designated CLA). Synthetically prepared CLA (containing all four isomers) was tested for anti-initiation activity in the two-stage mouse epidermal carcinogenesis system. Seven days, 3 days and 5 min prior to DMBA application, CLA was applied at doses of 20, 20 and 10 mg respectively. Control mice were treated similarly with linoleic acid or solvent (acetone). One week after initiation, and twice weekly thereafter, all mice were treated with 12-O-tetradecanoylphorbol-13-acetate to effect tumor promotion. There was no difference in tumor incidence or yield between linoleic acid-treated mice and solvent-treated control mice. By contrast, the CLA-treated mice developed only about half as many papillomas and exhibited a lower tumor incidence compared with the control mice.

Michael W. Pariza

Papers

Dietary sources of conjugated dienoic isomers of linoleic acid, a newly recognized class of anticarcinogens

Effect of conjugated linoleic acid on body composition in mice

The Biologically Active Isomers of Conjugated Linoleic Acid

Conjugated linoleic acid and atherosclerosis in rabbits

Anticarcinogens from fried ground beef: heat-altered derivatives of linoleic acid.