Food quality and shelf life21 / 22

In vegetables, blanching before freezing stops the enzymes; the time runs from 1.5 to 11 minutes depending on the vegetable. In fruit, ascorbic acid and a 40 percent syrup take the place of blanching.

The result of blast freezing meat depends on how long it rested after slaughter and how thick the pieces are. Meat frozen before rigor mortis has resolved contracts on thawing and stays tough.

Blast freezing is expected to take product core from +70 °C to -18 °C in at most 240 minutes; the real time is set by the thickest piece, packaging and load arrangement.

Blast cabinet air typically runs between -26 and -40 °C, but the process is not finished until the product centre is at -18 °C or colder. The end is decided by a probe in the product, not by the cabinet panel.

Blast freezing takes product quickly through the crystal zone between -1 and -4 °C. Ice crystals stay small and the product loses less water on thawing.

A tonne of broccoli gives off about 890 W at 20 °C and 62 W at 0 °C. Respiration heat by commodity from USDA data, the conversion factor and a worked example.

In hot holding the risk sits in the total time spent in the danger zone, not in a single reading. The log carries the service start time next to the temperature.

Container count comes from units simultaneously on route, returning, being washed or prepared. Use an event table to find the real peak.

Communiqué 2014/47 requires -18 °C or colder at every point of the product. The 3 °C allowance covers only short rises in transport, distribution and retail cabinets.

A small dairy delivers in its own car; by the fourth stop the yoghurt sours and the vacuum-packed cheese sweats. A boot holds no temperature; the cold has to move into the container.

Handle hot meals, chilled salads and ambient products separately during preparation and transfer; record handoff times by product.

Eutectic plates do not remove cooling energy, they move it into the depot. Below: GEBHARDT's plate table, Carrier's fuel figures and a worked calculation for one route.

Link chilled-product preparation, loading and final handoff records to the same batch; keep them separate from the hot-food flow.

The days on the label hold for one temperature only. If the product travelled at 8 °C instead of 4 °C, the days left change; here is the rough sum with Q10.

Validate a summer route with product measurements. Log waiting, sun exposure, lid openings and the final delivery together.

Screen each mixed load with a commodity table, separate producers from sensitive goods, and record exposure along the route.