Process improvements for preserving peak freshness in broccoli (2)
Despite broccoli’s image as a healthy, nutritious and flavoursome vegetable, sales are constrained by poor quality at retail and disappointing storability after purchase. A series of trials have been conducted examining how harvest, cooling and handling practices within supply chains could be affecting broccoli freshness at retail. Quality attributes including colour, rots and overall acceptability were assessed during storage at 7 or 16°C, these being the average temperature of broccoli in refrigerated and nonrefrigerated retail displays.
Storage quality was unaffected by time of harvest (6:00, 11:00 or 16:00) in Gatton during spring, even though soluble solids (including sugars) were significantly higher in broccoli harvested in the late afternoon. Late harvested heads also gained little weight during hydro-vacuum cooling, whereas those harvested in the morning gained 1−3%. This was the opposite result to what had been expected, and suggests that either the broccoli failed to fully hydrate overnight or that increased stomatal opening in the cool morning increased permeability to water.
Trials also examined the effect of cooling method (room cooling, hydro-cooling and hydro-vacuum cooling) on broccoli quality after transport to Sydney from Gatton (1 day) or Manjimup (1 week). The major differences were in weight gain or loss. Broccoli absorbed 2−7% moisture during hydro-vacuum cooling and hydro-cooling, a difference that was retained through to the end of storage life and is likely to improve head firmness. Although differences due to cooling method were not significant, this is likely due to cool harvest temperatures and the small quantities used for room cooling. There is considerable anecdotal evidence indicating that faster cooling does result in fresher broccoli at retail.
Delays between harvest and cooling greatly increased weight loss and reduced broccoli storage and shelf life. Differences were increased when broccoli was stored for an extended period and subjected to fluctuating temperatures within the supply chain – as occurred during transport from Manjimup to Sydney. All of the samples appeared in generally good condition on arrival, however clear differences appeared during storage at 7°C.