Transfer of heat and moisture during oven baking of potatoes

Abstract

Potatoes were baked for up to 60 min in a conventional fan-assisted oven. Temperature pro®les within the potato tubers were determined both by direct measurement and by following the inward progress of starch gelatinisation, which occurs at 65°C. Temperature pro®les with time were Sshaped and about 30 min was needed for the centre to reach 100°C. From the nature of the temperature pro®les, long potato tubers will cook faster than round tubers of the same weight, and a varietal`shape factor' was de®ned to quantify this effect. The slow temperature rise, compared to other forms of cooking, was due to evaporative cooling. Moisture loss was linear with time after an initial lag and reached 15±20% of the mass of the potato after 1 h of cooking. Approximately half of the moisture was lost from the outermost layer of the potato under the periderm, leaving behind a dried layer of¯esh that appeared to restrict water transport and, unlike any other part of the potato, could exceed 100°C. This has consequences for the thermal development of¯avour compounds as well as for perceived texture.

Transfer of heat and moisture during microwave baking of potatoes

“…Water loss measurements and the mapping of starch gelatinisation patterns were carried out as described in the preceding paper 2. Because microwave cooking did not give a simple inward‐moving starch gelatinisation front, the pattern of starch gelatinisation was recorded individually for each potato tuber examined and the percentage of the tuber cross‐section in which starch was gelatinised was measured by gravimetric integration.…”

“…Mean cutting force and cell separation after compressive fracture were measured as described previously 2. 6…”

“…During baking in a conventional oven, heat is transferred into the potato at its surface. The rate of heat transfer is limited by heat loss through water evaporation and by the reduced thermal conductivity of the dried ‘skin’ layer (see Ref 2 and references cited therein). Microwave cooking resembles oven baking in that there is substantial evaporative loss of water, but the conversion of microwave energy into heat is dispersed through the potato.…”

Database of processing techniques and processing factors compatible with the EFSA food classification and description system FoodEx 2

“…Baked potatoes can be prepared in a conventional oven, a convection oven, or a microwave oven (see chapter 3.7). Some restaurants use ovens designed specifically to handle large numbers of potatoes and keep them warm and ready for service (Wilson et al, 2002). Usually only domestic production or production of smaller quantities is relevant.…”

“…The yield factor is composed of a loss of water during heating in the oven (Wilson et al, 2002) and peeling (in the case of peeled baked potatoes) (BLS, 2009). The present document has been produced and adopted by the bodies identified above as authors.…”