Baby leaves are generally very perishable products with high respiration and water loss. The quality and postharvest shelf life of baby spinach can be affected by a range of pre-harvest factors such as genotype, maturity stage, growing conditions and proper harvesting time.
In baby leaves, significant improvements to postharvest shelf life have been described as being achieved by rescheduling the time of day for harvest to end-of-day harvest. Changes in leaf status can be due to the diurnal variation of environmental factors like temperature, light intensity and water supply, and in spinach some changes appeared to be related to variations in temperature and light intensity.
Spanish research team led by María I. Gil at Food Science and Technology Department (CEBAS-CSIC, Espinardo, Spain) investigated the effect of the time of day of harvest and the delay to processing on the quality of fresh-cut baby spinach. Physiological and quality characteristics were evaluated.
Two trials, one in winter (January) and another in spring (April), were compared so as to understand if there was any seasonality influence to optimize the time of harvest and the delay before processing of fresh-cut baby spinach. Three times of the day for harvest (8:30, 13:00 and 17:30 h as H1, H2 and H3, respectively) and three times of delay before processing (DP) (3, 24 and 48 h as DP3, DP24 and DP48, respectively) were studied.
It was found that at harvest the time of day for harvest affected transpiration rate and consequently the water content of baby spinach. In winter, the differences observed among harvest times were reduced when prolonging the delay to processing, while in spring these differences remained during storage. Time of day for harvest did not affect the quality of minimally processed baby spinach in winter.
However, in spring baby spinach harvested early in the morning (8:30 h) led to a product with higher water content, more vivid color, firm texture, good visual quality as well as lower respiration rate. In winter, delay before processing led to a reduction in the differences among harvest times but without differences between a delay of 24 and 48 h. However, in spring the best quality of the product harvested early in the morning was maintained with a delay before processing of both 24 and 48 h.
Scientists conclude that baby spinach for minimal processing could be harvested at any time in winter, while in spring it is recommended to harvest early in the morning. In addition, baby spinach can tolerate a delay before processing of at least 48 h without affecting its quality markedly.
Source: Yolanda Garrido, Juan A. Tudela, María I. Gil, 'Time of day for harvest and delay before processing affect the quality of minimally processed baby spinach', 2015, Postharvest Biology and Technology, Vol. 110, pages 9–17.
