Submitted to: Subtropical Technology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2010
Publication Date: N/A
Technical Abstract: Citrus sinensis (sweet orange, ex. Hamlin, Midsweet, Valencia) is the source of “orange juice” and juice must contain no less than 90% C. sinensis to be marketed as such. Juice produced from Citrus reticulata (mandarins) and C. reticulata hybrids (Orlando, Murcott, Fallglo, Sunburst, Minneola) can be blended with C. sinensis juice to improve color; however, mandarin juice cannot exceed 10% by volume of the finished product, and mandarin juice is not generally marketed. New mandarin hybrids with excellent flavor have potential for juice production, and could provide a diversification specialty juice for a niche market. Although there is considerable literature available regarding orange juice sensory characteristics, much less is known regarding juice from C. reticulata and C. reticulata hybrids. Two complex hybrid siblings that are ½ sweet orange, 3/8 mandarin, and 1/8 grapefruit have been identified as potentially useful sources of mandarin juice. However, initial sensory testing with a trained panel using frozen juice revealed some bitterness development in one of the hybrids. Bitterness results when the tasteless limonoic acid A-ring lactone (LARL) in juice is converted to the bitter compound limonin after juicing and has a negative impact on juice sensory quality. The objective of our study was to quantify the kinetics of bitterness development in juice of two mandarin hybrids (“A” and “B”) and compare results with ‘Navel’, a sweet orange known to develop bitterness. Fruits were harvested at weekly intervals from November to December of 2009, except ‘Navel’ which was only harvested in December, and juiced. Juice was divided into 4 one-L bottles and served to a trained panel within one hour of juicing, or after 4 and 24 hours at 10 °C. One additional bottle was frozen at -20 °C and served after 4 weeks. Aliquots of juice from each harvest and sampling time were taken and subsequently analyzed for titratable acidity (TA), soluble solids (SS), sugars, acids and limonoids (limonin, nomilin and their glucosides). Ten trained panelists rated the juice for sweetness, sourness and bitterness on a 0-10 scale. Half of the panelists could discern bitterness in hybrid B in samples stored for 24 hours as well as those that were frozen, but bitterness was not detected in hybrid A. Variation in perception of bitterness sensitivity to different bitter compounds is well-known, was observed in this specific group of tasters. Nevertheless, frozen stored ‘Navel’ juice was rated high in bitterness by all panelists. Hybrid A tended to be perceived as more sour, which correlated with higher TA and lower pH. Hybrid B had generally higher nomilin levels, regardless of sampling time. There were no sensory character differences due to harvest date, although the first harvest had the lowest pH and TA in hybrid B, and highest levels of nomilin and limonin in hybrid A. This study clearly showed sensory differences due to sampling juice at different times after processing for hybrid B and ‘Navel’ juices but not for hybrid A. Therefore, even though they both have potential for to be used for processing, hybrid B will have to be handled differently than hybrid A.