Curing, as a means of preserving fish, has been practised perhaps longer than any other food preservation technique. Marine fish bones found in cave dwellings, inhabited 20000 years ago and situated many days' walk from the coast of Spain, indicate some form of curing, probably by drying in the open air. Salting, smoking and drying have all continued as preservation techniques virtually unaltered from prehistory to the present day. Modern developments have centred around understanding and controlling the processes to achieve the standardised product demanded by today's market. A major exception has been exploitation of the sublimation of ice to dry food so that it resembled the starting material in volume and shape. This only became possible with the development of pumps which could create, and valve seals which could maintain, high vacuum.None the less, for all the developments in cure-processing accommodating continuous production lines, the time required to achieve a long shelf-life product purely by water removal is much greater than for any other commonly used preservation method. This is because the process relies upon the diffusion rate of either water from the centre of the food to its surface, or the diffusion rate of salt (or other solute) in the opposite direction, or a combination of both. Water content, water activity (a w ) and storage stabilityUnlike canning, which engenders the destruction of micro-organisms and their spores, curing preserves by rendering the medium an unsuitable environment for microbial propagation. Increasing the concentration of soluble substances in the medium either by abstracting water or by causing soluble substances to diffuse in (salting, brining or sugar curing) are the principal means of accomplishing this. In addition to concentrating the soluble substances by brining and dehydration, smoking preserves by depositing bacteriostatic chemicals like formaldehyde and phenols in the system.The addition of salt is more effective weight for weight than the addition of sugar because salt ionises to a sodium cation and a chloride anion each of G. M. Hall (ed.), Fish Processing Technology

No abstract

: The tortilla flour market is expanding but present industrial production is lagging behind in the use of modern technologies to increase production and cut costs due to the maize steeping and drying operations. A process using a singlescrew cook-extruder which eliminates the traditional steeping and drying operations was therefore explored. Lime (Ca(OH),) suspension was absorbed onto commercial maize grits (2 g lime kg-' maize) and the resulting meal conditioned to various moisture contents. These samples and one which had not been lime-treated were cook-extruded through a Brabender Do-corder extrusion cooker (Type 825602). The dry extrudate was milled through a I50 pm sieve and tortillas made from each sample. The tortillas prepared from the lime-treated grits conditioned to 472 g kg-' moisture compared favourably with that prepared from traditionally prepared masa flour when organoleptically assessed. Flour pasting properties (viscosity) and water absorption index were not significantly different ( P < 0.05) from the traditionally prepared products. Enzyme susceptible starch index did not correlate well with dough quality.

No abstract

No abstract