Title: Determination of blueberry and strawberry maturity and aroma quality and effect of HLB on orange juice aroma: comparison of Z-nose, E-nose and GC-MS technologies Authors
Submitted to: Subtropical Technology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 16, 2010
Publication Date: N/A
Technical Abstract: Electronic nose technology could be very useful in quality control discrimination of products. The Z-nose (Electronic Sensory Technology, Model 4500) was equipped with a Tenax trap (2 mg, 225 ºC), and 1 m DB5 column, an acoustic wave detector and an oven set to ramp from 40-180 ºC at a rate of 10 ºC/second. The instrument produces a simple chromatogram and can quantify total volatiles. The sampling time was 10 seconds with a blank run between samples to total 50 seconds total time/sample. This instrument was used to discriminate between strawberry samples, cultivar Florida Radiance, of varying maturity (white, half-red, commercially ripe, full ripe and over-ripe) and blueberry samples, cultivar Prima Donna, of varying maturity (green purple, purple-blue and dark-blue). The strawberries were harvested at the University of Florida Gulf Coast Research and Education Center in Wimauma, FL and the blueberries at a local farm in Haines City, FL. Fruits from several different plants were blended at high speed for 20 seconds, stored at -20 ºC until the headspace was thawed at 40 ºC for 20 minutes prior to sampling on the Z-nose or GC-MS. Subsamples were also sampled by a trained sensory panel. Results showed that the Z-nose could successfully discriminate the strawberry and blueberry samples of different maturity stages, based on their aroma volatiles as did the sensory panel based on flavor. The Z-nose chromatograms differed by fruit maturity similar to GC-MS chromatograms from the same samples. An electronic nose (E-nose) was also used to discriminate the strawberry and blueberry samples by maturity stage. For E-nose analysis, a FOX 4000 system (Alpha MOS, Toulouse, France) was used, fitted with 18 different metal-oxide gas sensors, some with coated surfaces. The electrical output from the sensors was measured at 0.5 seconds intervals. Samples 3 mL was sealed in a 10 mL vial with headspace replaced by argon gas to avoid oxidation. Vials with juice sample were incubated in an agitator at 500 rpm and 40 °C for 2 minutes before the headspace sample (500 µL) was taken from the vial and injected into the electronic nose. The carrier gas was pure air with a flow rate of 150 mL/minute. The electronic nose data acquisition program was a 2 minutes sampling time following by an 18 minute delay between samples for sensor recovery. Therefore the total sampling time/sample was 20 minutes. The E-nose also successfully discriminated among the different maturities for strawberry and blueberry. The E-nose was then used to discriminate among different Valencia and Hamlin orange juice samples to see if this equipment could discriminate between juice made from oranges from healthy or HLB-affected trees using asymptomatic or symptomatic fruit. The Valencia oranges were harvested in April and June and the Hamlin in January and December of 2009. The E-nose was able to discriminate between orange juice samples from healthy, asymptomatic and symptomatic fruit for both varieties and at each harvest date, indicating that these juice samples must differ in their volatile content. The December, 2009 Hamlin samples also included juice from HLB fruit from groves that received the Maury Boyd nutritional spray program and from groves that received conventional spray programs. These were also discriminated from each other and from healthy fruit for the most part. These data indicate the potential for Z-nose and E-nose technologies for use in screening for quality of fruit or juice products.