Effects of Blanching Method on Sugar and Protodioscin Contents of White Asparagus Spears

Abstract

In Japan, white asparagus spears are grown using two blanching methods to block sunlight: the traditional soilmound and the film-cover methods. The objective of this study was to investigate the influence of the film-cover and soil-mound methods on components of white asparagus spears related to flavor, especially sweetness and bitterness. We investigated the effects of the two blanching methods on sugar (fructose, glucose, and sucrose) and protodioscin (a major furostanol saponin in white spears) contents in white spears by conducting a spring field survey and an experiment using winter-forcing cultures. No significant differences were observed in sugar content or composition in spears cultivated by the two methods in either the field survey or the experiment. Protodioscin content tended to be higher in spears blanched by the soil-mound method than in spears blanched by the filmcover method in both the field survey and the experiment. These results suggest that differences in the flavor of white spears grown using the two blanching methods are caused mainly by bitterness associated with saponin content, and saponin content may be influenced by soil-borne stresses.

Methyl Jasmonate Treatment Enhanced Protodioscin Biosynthesis in White Asparagus (Asparagus officinalis L.) Spears

“…Although excessive bitterness decreases palatability, some consumers still prefer a degree of bitterness in asparagus. Protodioscin, a furostanol saponin compound, was confirmed as the principal saponin compound in white asparagus spears (Brueckner et al, 2010;Chin et al, 2002;Lee et al, 2010;Maeda et al, 2012;Schwarzbach et al, 2006;Shao et al, 1996;Wang et al, 2003). In a previous study, we found that blanching methods influenced the protodioscin content, but did not affect the sugar content .…”

“…Quantification method for protodioscin using HPLC equipped with an ELSD For the purpose of quantifying protodioscin content in asparagus, high performance thin layer chromatography (HPTLC) or HPLC equipped with a mass spectrometer (LC-MS) has been utilized (Brueckner et al, 2010;Maeda et al, 2012;Schwarzbach et al, 2006;Wang et al, 2003); however, both methods have disadvantages such as labor intensiveness, variability, low sensitivity (HPTLC), and relatively high initial and operational costs (LC-MS). Recently, a novel method using HPLC equipped with a UV detector was reported by Lee et al (2010).…”

“…Asparagus (Asparagus officinalis L.) is a popular vegetable in Japan (Kitazawa et al, 2011;Maeda et al, 2005Maeda et al, , 2010Maeda et al, , 2012. Although green asparagus is the commonly cultivated form in Japan, the consumption of fresh white asparagus has increased because of its pleasing taste.…”

“…Although green asparagus is the commonly cultivated form in Japan, the consumption of fresh white asparagus has increased because of its pleasing taste. White asparagus is produced using two blanching methods to block sunlight: the soil-mound and the film-cover methods (Jishi et al, 2008Jishi and Tanaka, 2009;Maeda et al, 2012). The soil-mound method has been widely used in many countries, including Japan (Heissner et al, 2006;Motoki, 2003;Siomos, 1996); however, the film-cover method is becoming popular in Japan because of its ease of harvesting.…”

Effect of Supplemental Light on the Quality of Green Asparagus Spears in Winter ‘Fusekomi’ Forcing Culture

“…Sample solutions were then centrifuged (10,000 rpm, 10 min) and filtered. Rutin content was determined by high performance liquid chromatography (HPLC) as described by Maeda et al (2012). HPLC analysis was conducted using a Waters Sunfire C18 (4.6 250 mm) column.…”