title: A comparison of juice extraction methods in the pungency measurement of onion bulbs.
abstract: BACKGROUND
  Onion pungency is estimated by measuring the pyruvic acid content in juice extracted from fresh tissues. We compared pyruvic acid content and its variation in the juices extracted by the pressing, maceration, blending with no water, or blending with water (blend/water) methods.
  
  
  RESULTS
  There were considerable differences in the pyruvic acid content and coefficient of variation (CV) among these methods, and there was an interaction between the onion cultivars and the juice extraction methods. The pressing method showed over 30% CV in the quartered or composite samples. The blend/water method showed the greatest pyruvic acid content in the shortday-type ('TG1015Y' and 'Texas Early White') onions, while the pressing method showed the greatest pyruvic acid content in the longday-type onions. The blend/water method, which gave ratios between 1:1 and 1:4 (w/w), showed the same pyruvic acid content. The blending (no water) method had the highest correlation, followed by the maceration method. The lowest correlations were found with the pressing method and the blend/water method.
  
  
  CONCLUSIONS
  Complete homogenisation of tissues with 1:1 or greater ratios of water was necessary for the maximum consistency and full development of the pyruvic acid reaction for onion pungency measurement.
authors.affiliation: Department of Horticulture and Life Sciences, Yeungnam University, Gyeongsan, 712-749, Republic of Korea.
authors.forename: Kil Sun
authors.identifier: http://orcid.org/0000-0002-9949-8990
authors.initials: KS
authors.lastname: Yoo
authors.affiliation: Department of Plant Science, Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, 151-921, Republic of Korea.
authors.forename: Eun Jin
authors.initials: EJ
authors.lastname: Lee
authors.affiliation: Vegetable and Fruit Improvement Center, Department of Horticultural Sciences, Texas A&M University, College Station, TX, 77843, USA.
authors.forename: Brian K
authors.initials: BK
authors.lastname: Hamilton
authors.affiliation: Vegetable and Fruit Improvement Center, Department of Horticultural Sciences, Texas A&M University, College Station, TX, 77843, USA.
authors.forename: Bhimanagouda S
authors.initials: BS
authors.lastname: Patil
mesh_terms: D005511:Food Handling / Q000379:methods*; D009812:Odorants / Q000032:analysis*; D019697:Onions / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry*; D019289:Pyruvic Acid / Q000032:analysis*; D012680:Sensitivity and Specificity; D014867:Water
chemical_list: D014867:Water; D019289:Pyruvic Acid
keywords: Allium cepa; flavour; pungency; standardisation; sweetness