Inland brackish-water recirculating aquaculture systems (RAS) must reuse water as much as possible due to challenges such as saline effluent discharge and inhibitory salt costs. Brackish water aquaponics systems using kale have been shown to reduce nitrate and phosphate that build up over time in RAS. Kale is marketable, but marketability of kale grown in saltwater is unknown. This trial analyzed sensory characteristics and preferences using a panel of volunteers who tasted Winterbor F1 kale grown in a range of salinities (0, 5, 10, 15 and 20 ppt salinity) in decoupled brackish water aquaponics systems containing reused shrimp culture water.
Participants (n=112) were presented with five raw kale samples (one from each salinity) and instructed to taste them in a counter-balanced order and rate their overall liking, taste liking, texture liking, and aftertaste liking on a 9-point hedonic scale anchored by “dislike extremely” and “like extremely”. Participants then rated their perceived intensity of basic tastes (sweet, salty, bitter) using a 0-100 line scale anchored by “not at all” and “extremely”. Following the sample evaluation, participants were presented with a brief description about aquaponics and asked whether this influenced their opinion and willingness-to-pay. Differences in liking and intensity were assessed using one-way ANOVA followed by Tukey’s post-hoc comparisons.
The 5 ppt kale was significantly more liked (overall liking, taste liking, and texture liking) than then 0 ppt kale. Focusing only on taste liking, the 5 ppt was also liked significantly more than both the 15 ppt and 20 ppt samples. No sample was liked less than the 0 ppt control. However, a closer examination of liking ratings revealed a bimodal distribution of the 20 ppt but not 5 ppt samples; in other words, participants were either “likers” or “dislikers” of the 20 ppt sample and very few provided a neutral rating. Aftertaste liking of kale samples grown in any salt concentration was significantly higher than the control 0 ppt sample. Saltiness intensity ratings increased in a dose-response manner, with the 10 ppt, 15 ppt, and 20 ppt samples all rated as significantly saltier than both the 0 ppt and 5 ppt samples. The 5 ppt sample was rated as significantly less bitter than the 0 ppt sample. Together, the saltiness, bitterness, aftertaste, and liking ratings suggest that a low level of saltiness in the kale samples masked the bitter kale flavor, which softened the aftertaste and improved taste liking. Information about aquaponics growing conditions resulted in an average willingness-to-pay of $2.06 USD per bunch, a 38% increase above the reference price of $1.49 USD. Overall, this study demonstrates that kale grown in brackish-water aquaponics is likely to be accepted by the consumer.