**3.4. Effect of production systems on antioxidant capacity**

Production systems significantly changed the TPC, TAC and ORAC, but the effects varied during the different harvests (**Table 4**). PMRC promoted TPC, TAC and ORAC of strawberry fruits compared to MRS throughout the harvest season. At early harvest, TPC, TAC and ORAC were significantly higher for PMRC than MRS, but the differences of TPC and TAC between PM and MRS were not significant (**Table 4**). At mid harvest, TPC, TAC and ORAC reached the peak, and PM showed a significant change of TPC and ORAC compared to MRS. PM showed a significant change of TAC compared to MRS until the late harvest (**Table 4**). The increase of TPC and TAC might be attributed to the changes of microenvironment temperature, moisture, various enzyme activities and rhizospheric microflora of soil under the PMRC compared to the MRS which promoted the growth stages similar to the finding of Wang et al. [19] who reported that fruits from hill plasticulture had higher flavonoid contents and TAC than the MRS. The fruits harvested from PMRC not only showed the higher TPC and TAC but also the better shelf life than those from MRS in our study. The relation between antioxidant activity and fruit shelf life could be explained by our previous research that some of the antioxidants may reduce the incidence of postharvest diseases during storage and be responsible for postharvest quality [34]. Similar results were found by Wang and Millner [35] which indicated that cultural systems affected ORAC values, flavonoids and anthocyanins of 'Allstar' and 'Chandler' strawberries. ORAC is another new method of measuring antioxidant


TPC and TAC were performed in triplicate for each of three replicates in 2009 and 2010.

TPC is expressed as micrograms of gallic acid equivalent (GAE) per gramme of fresh frozen weight; TAC is expressed as micromoles of Fe<sup>2</sup> SO<sup>4</sup> ∙7H<sup>2</sup> O equivalent per gramme of fresh frozen weight.

LSD (*p* < 0.05): least significant difference at the 0.05 level.

Different lower-case letters in the same column indicate statistically significant differences between different treatments (*p* < 0.05).

**Table 4.** Early-, mid- and late-harvest total phenolic content (TPC), total antioxidant capacity (TAC) and oxygen radical absorbance capacity (ORAC) of strawberry selection 'SJ8976-1' grown under three production systems.

capacities *in vitro*. Higher ORAC value indicates higher capacity to scavenge oxygen radicals. In other words, fruit harvested from PMRC showed higher ORAC value, which means PMRC enhanced the nutritional value of strawberry fruit.
