ISHS Acta Horticulturae 464: International Postharvest Science Conference Postharvest 96
RESPIRATION RATES OF CUT BROCCOLI |
| Authors: | D.W. Brash, X.F. Liu |
| Abstract:
Variation in respiration rate is an important factor to be considered when designing a modified atmosphere packaging (MAP) system. If any causes of variation are known, then packaging systems can be designed to take this into account, and the occurrence of injurious oxygen levels among individual MA packages can be avoided. We examined variation in respiration rate related to harvest date using broccoli heads collected from a commercial grower. Broccoli (cv ‘Shogun’) was harvested weekly during spring and early summer (12 harvests in total) from fields being used to supply the local market. Respiration rates at 20°C were measured on subsamples of branchlet and stalk tissue after 24 h. This information was used to estimate steady state respiration of whole heads. Head maturity was also assessed at harvest. Branchlets represented most of the weight (61 – 74%) and respiratory activity (82 – 87%) of broccoli heads. Whole head respiration rates after 24 h at 20°C varied markedly (204 – 307 mg CO2/kg/hr) and declined during the sampling period (Figure 1). Head weight varied but showed a strong upward trend (Figure 1). Head maturity at harvest, based on floret size, was variable, and declined during the sampling period (Figure 2). Correlations between variates indicated a negative relationship between whole head respiration rate and head weight (r = -0.418***) and a positive relationship between whole head respiration rate and head maturity (r = 0.390**). We conclude that broccoli MAP systems should take into account the wide variation in respiration rate detected in this experiment. Harvesting at consistent maturity and head weight could reduce variation in whole head respiration rate. This should be tested in future work. | |
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