IR technology to peel kiwis

Infrared (IR) technology has been studied as an alternative to conventional food processing technologies. The IR technology has attractive merits such as uniform heating, high heat transfer rate, reduced water, and energy consumption and improved product quality and safety. A few weeks ago, a study on the feasibility of kiwi peeling using infrared heating technology was published.

Researchers from the Gorgan University (Iran) used the response surface methodology (RSM) to investigate the effects of IR radiation power (250–850 W), the distance between IR emitter and sample (10–70 mm) and heating time (45–125 s) on the peeling performance and physicochemical properties of kiwifruit. Lye-peeling was used as the control treatment to compare the efficiency of IR peeling.

Photos of kiwis peeled with the Lye-peeling method with different immersing times: 3 min (a), 3.5 min (b), 4 min (c) and 4.5 min (d).

The Lye-peeling technology consists in immersing kiwis in a 150 g/l Sodium Hydroxide (Sigma, USA) solution at 95 °C for 3, 3.5, 4 and 4.5 min. The sample is then quickly held under tap water (20 °C) to avoid being cooked and remove the peel.

Photo of kiwis peeled using a knife (a),  using Lye-peeling (150 g/l, 95°C, 4 min) (b) and using infrared peeling (446 W, 70 mm, 125 s) (c).

"Heating with a power of 446 W at a distance of 70 mm for 125 s were found to be the optimum operating conditions for the IR peeling of kiwifruit. Under these conditions, we obtained a peelability of 90%, weight loss of 4.5%, peel thickness of 0.4 mm, surface temperature of 64.1 °C, puncture force of 57.7 N, color difference of 2.4 and ascorbic acid content of 140 mg/100 g. Compared to hot lye peeling, the IR radiation heating caused significant reduction in weight loss, surface temperature, and color differences. It also maintained the firmness of fruits," explained researchers

Source: Zahra Mohammadi, Mahdi Kashaninejad, Aman Mohammad Ziaiifar, Mohammad Ghorbani,'Peeling of kiwifruit using infrared heating technology: A feasibility and optimization study', 2019, LWT - Food Science and Technology, Vol. 99, pag. 128-137.

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