348 G. McCOLLUM AND E. BALDWIN
Therefore, a study was conducted on their thresholds by spiking
limonin and/or nomilin into: a simple matrix composed of sucrose and
citric acid; in a complex matrix of sucrose, glucose, fructose, malate,
and citrate (the major individual sugars and acids in orange juice) at
levels found in orange juice; and in orange juice itself. A three alter-
nate force-choice methodology was used (ASTM 1997), and the effect
of sucrose or citric acid on perception of bitterness was also investi-
gated (Dea et al. 2013). It was determined that, in a 1:1 ratio, the com-
bination of limonin and nomilin acted synergistically to decrease their
combined thresholds to a level that occur in orange juice (especially if
affected by HLB), thus explaining why panelists perceived bitterness
in HLB-affected juice. Added sucrose decreased the perception of bit-
terness induced by these bitter limonoids and it was also noted that
nomilin imparted a metallic taste that is often one of the descriptors
for HLB juice. For orange juice, adding limonin and nomilin increased
perception of bitterness, but this increased bitterness perception was
reduced if sucrose was added for both “Hamlin” and “Valencia” juices
(Dea et al. 2013). Thus, as is the case with HLB-affected fruit, when
sugars decrease and bitter limonoids increase, the bitterness is more
perceivable.
C. Management of Off-flavor for the Orange Juice Industry
Since it has been determined that HLB disease does affect fresh fruit
and juice flavor quality, research was conducted to develop methods
to manage the off-flavor. For the juice industry, there are management
techniques that can be employed using blending and quality screening
of juice, which unfortunately, will not be useful for fresh fruit. Blending
juices of different varieties and seasons is an important technique used
by citrus processors to maintain a consistent quality of juice, with a
consistent color and solids/acid ratio (Kimball 1999). Therefore, blend-
ing juices from different sources then gives juice processors flexibility
to balance out the juice characteristics to an acceptable bitterness level
(Bates et al. 2001). This was demonstrated with bitter “Kinnow” man-
darin juice by blending in pomegranate juice (Bhardwaj and Mukherjee
2011). In the case of HLB-affected orange juice, the undesirable charac-
teristics of HLB juice could be mitigated by blending with healthy juice.
To demonstrate this possibility, healthy orange juice was blended with
various amounts of HLB-affected juice made from fruit symptomatic for
the disease using both “Hamlin” and “Valencia” juices (Raithore et al.
2015). The healthy juice, HLB juice, and all blends were chemically
analyzed for sugars, acids, and bitter limonoids as well as by a sensory