Blanching Step Research Articles

APPLICATION OF LOW TEMPERATURE HEAT TREATMENTS BEFORE RETORTING IMPROVES THE QUALITY OF CANNED POTATOES

Low temperature heat treatments applied to potatoes (cv Atlantic, Snowden, and Pike) prior to retorting were evaluated for their effect on sloughing in canned potatoes. Blanching in water for 30 min at 60 - 77C before retorting decreased potato breakage, brine turbidity, and brine soluble solids without adversely affecting firmness or color. Low temperature blanching was only effective when potatoes were retorted in CaCl 2 (0.1 %) brine solutions. Sloughing was also decreased by a hot-fill and hold process that utilized brine fill temperatures of 77 - 93C followed by a 30 min hold in CaCl 2 (0.1%) brine before commercial sterilization. The hot-fill and hold method for control of sloughing in canned potatoes is an improvement over current methods because it eliminates the need for a blanching step and requires only minimal changes in equipment or product flow.

Optimisation of freezing process with pressure steaming of potato tissues (cvMonalisa)

Response surface methodology (RSM) was used for determining optimum conditions of the freezing process on pectinesterase (PE) activity, rheological parameters and textural properties in potato tissues. In the process of production of frozen potatoes, the second step of the stepwise blanching prior to freezing was considered as a fixed factor and performed at 97 °C for 2 min as well as the freezing rate in the freezing step itself, which was carried out at -2 °C min -1 . The effects of variation in levels of temperature (57.93-72.07°C) and time (15.86-44.14 min) in the first blanching step on the PE activity were studied using a central composite rotatable design. A Box-Behnken factorial design was used to investigate the effects of simultaneous variation of temperature (60-70 °C) and time (20-40min) in the first blanching step and steaming temperature (112-122°C) and time (1-3 min) on rheological parameters and textural properties. Blanching temperature was the independent variable that most influenced either enzymatic activity or rheological parameters. Stationary points showing maximum PE activity had critical temperature and time values of 64.22°C and 29.37min before freezing and 64.39°C and 28.02min after freezing and steaming of the tissues, and these values were very close to those obtained for some creep compliance parameters. Results show a high correlation between increases in PE activity and tissue firmness below optimum experimental freezing conditions, proving the role of the enzyme as one of the main contributors to the firmness which determines the textural quality of frozen potato tissues.

Liberation of free fatty acids during production of potato granules

The amount of free fatty acids and their composition were studied during an add-back process of potato granules. Samples were taken at several different stages in the production, from raw tubers to final potato granules. Lipids were extracted and lipid classes separated by liquid chromatography. Free fatty acids were separated from the neutral lipid fraction by high performance liquid chromatography (HPLC). The fatty acid composition was analysed by gas chromatography (GC). The amount of free fatty acid increased in the first stages of the process and rose to its highest level in the samples from the steam-cooking step. During further processing the amounts of free fatty acids slowly decreased. Since enzymatic hydrolysis is one explanation for liberation of fatty acids, lipase activity was measured by a spectrofluorimetric method in the raw tubers, blanched slices and steam-cooked slices. After the blanching step, some enzyme activity was found but after steam-cooking there was none.

Work to start soon on Government Atomic Laboratory at Schenectady

The present study aimed at evaluating the potential of an integrated process based on the use of membrane technology and adsorbent resins for the recovery, concentration and purification of phenolic compounds from artichoke wastewaters.In particular, artichoke wastewaters coming from the blanching step were pre-treated by ultrafiltration (UF) in order to remove suspended solids and macromolecular compounds. The UF permeate was submitted to a nanofiltration (NF) process producing a concentrated fraction enriched in phenolic and sugar compounds.Three different macroporous resins were tested through adsorption/desorption methods to produce purified phenolic fractions with high antioxidant activity. Samples produced in UF, NF and adsorption–desorption tests were assayed for phenolic composition (chlorogenic acid and apigenin 7-O-glucoside), sugar composition (fructose, glucose and sucrose) and antioxidant activity.Among the three different tested resins, the S 7968 offered the best performance in terms of adsorption/desorption ratio for chlorogenic acid, with a total adsorption/desorption yield (TADY) of 63.39%; for the apigenin 7-O-glucoside the S 7968 and the S 2328 resins showed a TADY in the range 68.31–78.45%.