ISSN:8755-9129    

DOI:10.1080/87559129309540966

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

“Sustainable agriculture” has been defined as a farming system with a low external input of agrochemicals, particularly fertilizer nitrogen. The impact of such farming systems on the quality of three arable crops was considered. Rape seed, wheat, and potato were selected, because they represent arable crops with simple to complex quality criteria.Rape seed(= simple quality criteria): The oil quality is determined primarily by the genotype and is only slightly affected by environmental conditions and cultural practices such as low nitrogen supplies. Within three decades, conventional breeding has changed rape seed into a new crop providing oil for human consumption instead for technical purposes.Wheat(= more complex quality criteria): Wheat is an excellent source of highly digestible energy for human consumption, but its most important quality criterion is the content of protein, which is positively correlated with baking quality and with contents of essential amino acids such as lysine and methionine. Since nitrogen is a constituent of protein, farming systems with little or no fertilizer nitrogen necessarily produce wheat less suited for bread making and of lower nutritional value. At low nitrogen supply, high‐protein wheat can be produced only if the grain yield is kept low. Nitrogen fertilization has only a small impact on the contents of vitamins and minerals. Reductions in phosphorus fertilization decrease the grain phosphorus content but may increase grain zinc content.Potato(= complex quality criteria): As compared to wheat, quality traits of potato are less affected by cultural practices. High potassium levels are essential for tubers of high quality. In contrast, high nitrogen inputs can have adverse effects on several quality traits. The use of pesticides and growth regulators most often has no direct effects on the quality of seeds and tubers. Generally, customers should be willing to pay more for food which is of a high ecological quality but may be inferior in technological and nutritional quality.

ISSN:8755-9129    

DOI:10.1080/87559129309540967

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Genetic modification of microorganisms has been applied to the production of food enzymes such as chymosin, and to the optimization of traditional microorganisms used in the fermentation of food such as baker's yeast and lactic acid bacteria. Chymosin produced with genetically modifiedEscherichia coli K12, Kluyveromyces lactis, andAspergillus nigersubsp.awamorihas been accepted by some markets in about 20 countries and therefore entered the human food chain. However, genetically modified baker's yeast has it much harder achieving acceptance although it has been approved in the United Kingdom. Genetic engineering of food systems is not a matter of the inventing scientists and industries only, it is as much a matter of acceptance by the consumer and the general public. It is the scope of this review to describe the biotechnology of the chymosin and baker's yeast systems, and to outline some other systems such as the lactic acid bacteria. The technical description is supplemented with information on safety assessment, regulation, and labeling, as well as the theory and practice of risk perception and acceptance of such products by the general public.

ISSN:8755-9129    

DOI:10.1080/87559129309540968

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Over the last 5000 years cereals have been bred for food, feed, and beverages by selection of spontaneous mutations and random hybrids. Since the turn of the century, crosses with defined parents, and since 1927 artificially induced mutations, have been used to create variability on which selection of new varieties is based. It is pointed out that hybrid corn and transfer of rust‐resistant genes from wild species into chromosomes of bread wheat was preceded by decades of basic research. Genetic transformation is an additional tool for the breeder to introduce novel genes in a rational manner and will complement but not replace the existing efficient breeding methods. Genetic transformation has been demonstrated in maize, rice, and wheat, while techniques to obtain transgenic barley plants are still being developed. Our present knowledge on the endosperm‐specific expression of storage proteins and the modulation of this expression by transcriptional activators is reviewed. Breeding strategies for altered protein quality and for proantho‐cyanidin‐free malting barley are presented. Engineering of an improved malt enzyme, a heat stable (1–3,1–4)‐β‐glucanase, is described. The enzyme is expected to survive, like α‐amylases, the kilning process and has been shown to act efficiently in the mashing process for the elimination of water‐soluble β‐glucans which impede filtration of wort. The engineered enzyme is expressed in transformed aleurone protoplasts and secreted from these cells and thus shown to be operational in the tissue, where it is expected to work. Hormone‐regulated promoters for the expression of genes acting during grain development and malting have been characterized. Prospects for the production of polyhydroxyalkanoates and cyclodextrins in cereal grains are discussed.

ISSN:8755-9129    

DOI:10.1080/87559129309540969

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

During the past decade, scientists have learned how to transfer re‐combinant genes into the genomes of livestock to produce “trans‐genic” animals. Microinjection of ova with copies of a gene is the primary method used, but the efficiency is low. About 1% of injected ova result in transgenic offspring. Initial research primarily involved genes encoded for growth hormone (GH). The GH transgenes that have thus far been used result in high concentrations of GH being produced throughout life. In general, GH (bovine) pigs did not grow larger than their sibs, but they gained weight up to 13% faster and they were 18% more efficient in utilizing feed. The excess GH dramatically altered carcass composition in comparison to sibs. At 92 kg, carcasses of GH pigs had 85% less total fat, which consisted of 85% less saturated fatty acids (SFA), 91% less monounsaturated fatty acids (MUFA), and 66% less polyunsaturated fatty acids (PUFA) than sibs. In primal cuts of GH pigs, intramuscular fat was reduced 43% in ham, 66% in loin, 64% in shoulder, and 69% in belly. No significant differences were detected in meat tenderness (shear force) for GH transgenics and sibs. Persistent excess GH in transgenic pigs was detrimental to their health. These problems were of such magnitude that these pigs could not be used for farming. When molecular biologists know more about gene regulation, transgenes can be constructed in which GH secretion might be tightly regulated. At that time, transgenic swine may be produced with positive attributes provided by a GH transgene, or other transgenes, with potential to improve carcass merit without adversely altering the health status of transgenic swine.

ISSN:8755-9129    

DOI:10.1080/87559129309540970

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:8755-9129    

DOI:10.1080/87559129309540971

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:8755-9129    

DOI:10.1080/87559129309540965

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor