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A major difference between sterilised foods (canned and bottled) and foods preserved by other methods, such as dehydration and freezing, is that sterilisation destroys the micro‐organisms that would otherwise destroy the food, whilst the other methods of preservation create an environment hostile to the micro‐organisms present in the food. In practice, this makes packaging of foods to be sterilised much more critical than packaging of foods preserved by other means. Leakage of small quantities of water into packages of dehydrated foods, for example, will shorten the storage life of the product but, unless gross leakage occurs, immediate deterioration will not occur. With a sterilised food, even the penetration of a single bacterium into a package can bring about the almost immediate demise of the food because the environment inside the package is usually ideal for microbiological growth. Fig. 1 shows the typical effect of leakage on sterilised and dehydrated foods. The perfect seal necessary for sterilised foods has, historically, been the main reason for the slow introduction of flexible pouches for sterilised foods, but modern technology now permits adequate seals to be made in suitable flexible materials and these are playing an increasingly important role.

Unless foods are treated very soon after harvest or slaughter, most will deteriorate rapidly due to the action of bacteria and other micro‐organisms. This microbial deterioration usually manifests itself by the typical signs of putridity, fermentation or mouldiness, but most hazardous are those bacteria that can grow to dangerous concentrations without obvious signs that they have done so. The main aim of food preservation processes is to create an environment unsuitable for microbial growth or, with processes such as canning, to destroy the micro‐organisms in the food and to pack the food so as to prevent subsequent ingress by other organisms. Micro‐organisms will not grow at very low temperatures, in low water concentrations, in high acid, salt or sugar concentrations or in the presence of certain chemicals. Thus, freezing, dehydration, pickling and salting are effective in preserving foods. Heat also destroys micro‐organisms and is used in canning and bottling and in pasteurisation, which is a partial preservation process.

A number of methods are used, or have been proposed, for improving the tenderness of otherwise tough meat. Of these, preparations containing proteolytic enzymes to break down meat proteins are the most widely used. They do work but they cannot turn cowheel into fillet and they cannot imitate adequately the subtle post‐mortem changes that naturally produce top quality meat.

One of the most satisfactory methods of preserving foods for long periods is the process of canning, in which the food is sealed into a container and then sterilised by heat. Modern canning lines are capable of handling up to 2000 cans per minute, but the geometry of the can and the low thermal conductivity of food place constraints on the maximum heating temperature and type of food that can be canned. ‘Aseptic’ canning processes overcome these constraints by sterilising food in specially designed heat exchangers before it is filled into sterile cans. Such processes allow high sterilising temperatures to be used, resulting in improved product quality.

With a modest selection of reagents, equipment and test foods — some of which will be normally stocked in the kitchen — students can carry out these practical tests. Most of them will be aware that certain foods develop a brown pigmentation during processing, preparation and cooking. A number of different reactions can cause this browning; reactions between amino‐acids and sugars are responsible for the surface colour of baked bread, caramelisation of sugars produces the colour of toffee and oxidation of some food components can produce discolouration in orange juice. Another familiar browning reaction is that which produces rapid discolouration in cut or bruised fruits and vegetables such as potato, mushroom and apples. These reactions — known as ‘enzymic browning’ because they are catalised by an enzyme present in the food — are the subject of this article.

Fruit and vegetables after harvest remain in a living state; they respire using the reserve carbohydrates and organic acids and are capable of enzyme interconversions of their constituents. Processes like ripening continue after harvest but, because the harvested commodity has only a limited supply of reserve carbohydrate and is removed from its normal source of water, premature senescence and wilting may be promoted. The harvested commodity is susceptible to mechanical damage which can lead to bruising and a combination of senescence and damage can give increased susceptibility to fungal and bacterial rotting. The browning reaction which results when fruits or vegetables are bruised or cut is due to the action of the enzyme polyphenoloxidase on phenolic compounds producing quinones which then polymerise to produce the familiar brown or black pigments. Post‐harvest treatments are designed to minimise these deleterious effects while controlling processes such as ripening so that the commodity can be sold in the optimal condition.

This paper aims to elaborate on the concept of avoided emissions, as a topical issue in the carbon accounting debate, both in practice and in academia. It is a commentary on the paper by Revellino (2019) who analyses an avoided emissions technology in the transport sector.

This is a commentary based on secondary data analysis.

This commentary reviews the history of quantification for avoided emissions and elaborates on three major challenges that project using “avoided emissions” face. This commentary is also a reflection on why avoided emissions calculations are needed in a world of transition, and how this leads to the concept being used and abused while being central to the building of new foundations.

The commentary flags a few areas that could be research focus areas in future.

This paper can lead to changes in the public perception of “avoided emissions” and corporate claims around emission avoidance.

This commentary outlines clear avenues for research, asking notably to reflect on the acceptable uses and acceptable claims related to avoided emissions.

Significant effort has been made to support pre-service and novice teacher learning in the K-12 context. Less attention has been paid to promoting pre-service and novice second language teacher learning via collaboration with peers and more expert educators at the university level. In order to facilitate this type of teacher collaboration, a mentoring project was incorporated into the existing practicum of a Master of Arts in Teaching English as a Second Language (ESL) program at a US University. The purpose of this paper is to examine the nature of the mentoring experiences of four ESL mentor-pre-service teacher pairs in the US University context.

For this research project, eight teachers – four mentor-pre-service teacher pairs – participated as pairs in mentoring sessions focussed on activities such as co-planning, co-teaching, and co-reflecting on teaching. Informed by a sociocultural perspective on teacher learning (Vygotsky, 1978), this study presents case studies of all four pairs in order to demonstrate the complex nature of mentoring. The data analysis focussed on the content of the teachers’ interactions and their perceptions of the mentoring experience.

The study traced the developmental trajectories of the participating teachers over one 15-week academic semester. The study uncovered some critical contradictions that the participants encountered during the mentoring experience, thus pointing to its complexity. The study also uncovered the varied nature of mentoring: whereas in one pair the mentor acted as a more expert other (Vygotsky, 1978), in another pair, the mentoring relationship was more reciprocal.

This study showed that pre-service teachers can develop further through mentoring. Such mentoring can help teachers gain confidence and share teaching strategies. At the same time, the study revealed certain challenges associated with introducing a mentoring project in a pre-service teacher practicum. It is recommended that program faculty as a whole read the rich dialogues produced by participating teachers engaged in relationships focussed on collaborative learning, thereby discovering a foundation for revisions that go beyond individual teaching practices to the programmatic level.

This study’s principal contribution to the field is that it showcases the complex nature of mentoring experiences and the ways in which they differ from each other.

Reviews the issues arising out of an annual series of conferences, Information for Scotland, held since 1993. Three main contexts are identified and issues examined: marketisation and globalisation, convergence and regrouping, the Scottish Parliament and democratic renewal within the political context; the new agenda for learning within education; and the rise of electronic networks within technological change, are all discussed in the context of papers delivered at the conferences.