Nutrient requirements of dairy cattle , Nutrient requirements of dairy cattle , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Nutrient requirements of dairy cattle

Listeria monocytogenes is a Gram positive, aerobic, facultative anaerobic and nonacid fast bacterium, which can cause the disease listeriosis in both human and animals. It is widely distributed thoroughout the environment and has been isolated from various plant and animal food products associated with listeriosis outbreaks.

Contaminated ready-to-eat food products such as gravad and cold-smoked salmon and rainbow trout have been associated with human listeriosis in Sweden. The aim of this study was to analyse the occurrence and level of L. monocytogenes in
gravad and cold-smoked salmon (Salmo salar) products packed under vacuum or modified atmosphere from retail outlets in Sweden. Isolated strains were characterized by serotyping and the diversity of the strains within and between
producers were determined with PFGE (Pulsed-field gel electrophoresis). The characterized fish isolates were compared with previously characterized human strains.
L. monocytogenes was isolated from 11 (three manufacturers) of 56 products analysed. This included gravad salmon products from three manufacturers and cold-smoked salmon from one manufacturer. The highest level of L. monocytogenes found was 1500 cfu/g from a cold-smoked salmon product but the level was low (<100 cfu/g) in most of the products. Serovar 1/2a was predominant,
followed by 4b. Three products of gravad salmon harboured more than one serovar. PFGE typing of the 56 salmon isolates detected five Asc I types: four types were identical to human clinical strains with Asc I and one was identical and one was closely related to human clinical strains with Apa I. Isolation of identical or closely related L. monocytogenes strains from human clinical cases of listeriosis and gravad and cold-smoked salmon suggested that these kinds of products are possible sources of listeriosis in Sweden. Therefore, these products should be considered risk products for human listeriosis.

Listeria monocytogenes, a food-borne pathogen

The principal pathways for the formation of flavour compounds in cheese (glycolysis, lipolysis and proteolysis) are reviewed. Depending on variety, microflora and ripening conditions, lac- tate may be metabolized by a number of pathways to various compounds which contribute to cheese flavour or off-flavours. Citrate metabolism by citrate-positive lactococci or Leuconostoc spp. is important in certain varieties (e.g., Dutch cheeses). Lipolysis results directly in the formation of flavour compounds by liberating free fatty acids (FFA). FFA may also be metabolized to alkan-2-ones and fatty acid lactones. Proteolysis of the caseins to a range of small- and intermediate-sized peptides and free amino acids (FAA) probably only contributes to the background flavour of most cheese varieties, but FAA are important precursors for a range of poorly-understood catabolic reactions which produce volatile compounds essential for flavour.

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Biochemical pathways for the production of flavour compounds in cheeses during ripening: A review

Bacteriocin-based Strategies for Food Biopreservation

Rennet-coagulated cheeses are ripened for periods ranging from about two weeks to two or more years depending on variety. During ripening, microbiological and biochemical changes occur that result in the development of the flavour and texture characteristic of the variety. Biochemical changes in cheese during ripening may be grouped into primary (lipolysis, proteolysis and metabolism of residual lactose and of lactate and citrate) or secondary (metabolism of fatty acids and of amino acids) events. Residual lactose is metabolized rapidly to lactate during the early stages of ripening. Lactate is an important precursor for a series of reactions including racemization, oxidation or microbial metabolism. Citrate metabolism is of great importance in certain varieties. Lipolysis in cheese is catalysed by lipases from various source, particularly the milk and cheese microflora, and, in varieties where this coagulant is used, by enzymes from rennet paste. Proteolysis is the most complex biochemical event that occurs during ripening and is catalysed by enzymes from residual coagulant, the milk (particularly plasmin) and proteinases and peptidases from lactic acid bacteria and, in certain varieties, other microorganisms that are encouraged to grow in or on the cheese. Secondary reactions lead to the production of volatile flavour compounds and pathways for the production of flavour compounds from fatty acids and amino acids are also reviewed.

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Biochemistry of Cheese Ripening

High-pressure processing (HPP) is a nonthermal process capable of inactivating and eliminating pathogenic and food spoilage microorganisms. This novel technology has enormous potential in the food industry, controlling food spoilage, improving food safety and extending product shelf life while retaining the characteristics of fresh, preservative-free, minimally processed foods. As with other food processing methods, such as thermal processing, HPP has somewhat limited applications as it cannot be universally applied to all food types, such as some dairy and animal products and shelf-stable low-acid foods. Herein, we discuss the effects of high-pressure processing on microbial food safety and, to a lesser degree, food quality.

High‐pressure processing – effects on microbial food safety and food quality

Background Rice is a staple food and an important source of proteins in many regions worldwide. Its protein component is generally regarded as hypoallergenic, and a number of studies have highlighted the nutritional and health benefits associated with consumption of rice proteins. In recent years, the processing of plant proteins has drawn scientific and industrial interest, and rice protein-enriched ingredients have become commercially available. Scope and Approach The aim of this study was to provide a critical review of the state of the art regarding the composition, extraction methods, functional properties and applications of rice proteins. Key Findings and Conclusions Rice is composed of four protein fractions, namely albumin (water-soluble), globulin (salt-soluble), glutelin (alkali-soluble), which represents the dominant protein in brown and milled rice, and prolamin (alcohol-soluble), a minor protein in all rice milling fractions. Different methods to extract proteins from rice, including alkaline, enzymatic and physical methods, have been, and continue to be, evaluated for their efficacy, and some have been applied industrially. However, only a limited amount of studies have described the functional properties of rice proteins and how these can be improved by means of enzymatic hydrolysis. Applications of intact rice proteins are limited due to their poor solubility in water. However, hydrolysed rice proteins are used in the formulation of hypoallergenic infant formulas and may potentially be used in a variety of food systems due to their improved functionality. Despite the advances in the characterisation of rice proteins, a greater understanding of their physicochemical properties and how to modify their functionality is required in order to expand their range of food applications.

The composition, extraction, functionality and applications of rice proteins: A review

Indigenous enzymes in milk: Overview and historical aspects—Part 1

Publisher Summary
The application of any new technology presents significant challenges to food technologists and food researchers. High-pressure (HP) processing offers the food industry a technology that can achieve the food safety of heat pasteurization while meeting consumer demand for fresher-tasting minimally-processed foods. In addition, other favorable organoleptic, nutritional, and rheological properties of foods have been demonstrated following HP, in comparison to heat processing. The retention of color, aroma, and the preservation of nutritive components are enormous benefits for both food processing industry and consumers. Also, from a food processing/engineering perspective, key advantages of high-pressure applications of food systems are the independence of size and geometry of the sample during processing, possibilities for low temperature treatment, and the availability of a waste-free, environment-friendly technology. Application of HP can inactivate microorganisms and enzymes and modify structures while having little or no effects on nutritional and sensory quality aspects of foods. HP food processing today is being used on an ever-increasing commercial basis. Opportunities clearly exist for innovative applications and new food product development. HP can affect the functionality of protein and carbohydrate molecules often in unique ways, which may allow optimization of food manufacturing processes and production of novel foods. The range of commercially available HP-processed products is relatively small at present, but there are opportunities for further development and production of a wide range of HP-treated products.

High-Pressure Processing of Foods: An Overview

Many commercially important shellfish are filter feeders and, as a consequence, concentrate microbes from the surrounding waters. Shellfish may be relayed or depurated to reduce the level of microbial contamination, but the efficiency of these purification practices, particularly in relation to viruses and indigenous marine bacteria, is questionable. Therefore additional processing is necessary to ensure the safety of shellfish for human consumption. In recent years high pressure (HP) processing has been investigated as an alternative method for food preservation. HP technology allows inactivation of microorganisms while maintaining sensory and nutritional properties of foods. Currently, HP processing has several commercial food applications, including oysters. As well as enhancing safety and extending shelf-life, HP treatment has the additional advantage of shucking or opening shellfish, making this technology particularly beneficial to the shellfish processing industry and consumers alike. Industrial relevance High pressure (HP) processing is increasingly being used in the commercial processing of oysters, due to its minimal effects on sensory and nutritional quality, the opening or shucking of oysters during treatment, and the reduction of levels of Vibrio vulnificus , a pathogen of concern particularly in the US. However, little is known of the efficacy of HP treatment in reducing other pathogens in shellfish such as human enteric viruses, which are the predominant cause of shellfish-borne disease. This article reviews the inactivation of microorganisms of importance to shellfish, particularly viruses, the commercial HP processing of oysters and the advantages of HP technology as they pertain to the seafood industry.

Alan L. Kelly

Papers

High‐pressure processing – effects on microbial food safety and food quality

The composition, extraction, functionality and applications of rice proteins: A review

Indigenous enzymes in milk: Overview and historical aspects—Part 1

High-Pressure Processing of Foods: An Overview

High pressure processing of shellfish: A review of microbiological and other quality aspects