Effect of harvesting time and moisture on mechanical properties of garlic (Allium sativum L.) skin

Abstract

Splitting or cracking of the outer skins reduces the garlic storage life-time and its marketability.  To determine the parameters which affect the mechanical properties of garlic skin, white and pink bulbs were taken for this study. Bulbs were harvested in 3 stages, namely 10, 20 and 30 days after cutting off the irrigation.  Bulbs were cured in shade at 23±1ºC for 2, 9, 16 and 23 days.  Then, dried skins were treated for 5 days at the ambient temperature of 23ºC and relative humidity (RH) of 17%, 38%, 55%, 77% and 95%.  The moisture content, thickness and strength, stiffness, stress and strain at breakage were measured. Results showed that at later harvesting and during curing, moisture content, thickness and burst pressure decreased.  It was revealed that the multi-directional strength reached its maximum when the skin moisture content of white ecotype and pink cultivar reached 21.28% and 31.72%, respectively.  The irrigation having been cut off, the skin strength reduced rapidly after 28 days for white ecotype and 18 days for pink cultivar.  The skin strain increased and consequently stiffness decreased when moisture contents were higher than 20%.  Moreover, moisture content, thickness, burst pressure and strain at breakage of skins increased with the increase of incubation in relative humidity while the stress and stiffness decreased.  Furthermore, pink cultivar skins as compared to white skin were broken with less force easily.

Keywords: garlic, skin, moisture, cracking, strength, postharvest