| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 89 === Bitter compound is known as important quality index in Buntan Shaddock ( Citrus grandis (L.) Osbeck, one variety of pummelos ) juice. Two groups of bitter compounds are found in Buntan Shaddock juice: narigin which found in flavanone glycoside and limonoid, which included of limonin and nomilin. Content of limonin and nomilin in Shaddock decreased during postharvest storage whereas no significant decrease was observed in naringin. Titratable acid, Ascorbic acid decreased during storage time, but soluble solids, protein, formaldehyde nitrogen and total phenol were increased. Buntan Shaddock juice prepared by no removal of segment membrane contains higher bitter compound than that of segment membrane removed juice.
Naringin was found the highest bitter compound in Shaddock juice. In resin naringin debittering model solution models experiment, 5L model solution was treated by 50 g, 100 g of XAD-16 and 50 g and 100 g of XAD-7HP, the debittering ability was 59.5 %, 96.7 %, 42.6 % and 87.1 % respectively. In 200 mg/ L model solution, debittering ability of 50 g of XAD-16 and XAD-7HP was found to be 86.8 % and 64.3 %, respectively. It was also found that the higher amount the treated juice, the higher concentration of bitter compound could be found in Shaddock juice. After 4 L of Shaddock juice treated by two above resins, its bitter compound was found within the threshold concentration. In juice prepared without removal of segment membrane, limonin reached threshold concentration when XAD-16 and XAD-7HP were added to 0.4 L and 0.6L of Shaddock juice; Nomilin reached threshold con- centration at 0.6 L and 0.8 L; Naringin reached 500 mg/ L in 2.0 L and 1.6 L.
The adsorption ability of above resins was investigated. After 4 L of Shaddock juice treated by 50 h XAD-16 and XAD-7HP, removing rate of limonin was 75.7 % and 78.9 %, respectively; removing rate in nomilin was 88.2% and 90.1 % whereas in naringin was 83.6 % and 74.0 %, respectively. In juice prepared without removal of segment membrane, removing rate of limonin was 62.8% and 58.4 %, nomilin was 78.1% and 69.8% and naringin was 32.5% and 26.9%. It indicated that XAD-7HP have better ability in debittering of limonin and nomilin, whereas XAD-16 better at the debittering of naringin, and adsorptive space of XAD-16 was higher. In the regeneration of resins, after been used for three time, absorption ability of XAD-16 and XAD-7HP to limonin, nomilin and naringin were dropped in 3.0% and 2.9%, 1.6% and 2.0%, 29.4% and 6.4%, respectively. As a result, XAD-7HP have better regeneration performance.
Juice treated with XAD-16 has no significant difference in its titratable acid and ascorbic acid changes but decrease in protein and total phenol. XAD-7HP caused no change in titratable acid but decrease in ascorbic acid, protein and soluble solid. The adsorption of pigment by these resins also caused the increase of L and a value and decrease of b value. In summary, XAD-16 has better performance in debittering of naringin and also caused small change in juice components; XAD-7HP has better debittering performance in limonin and nomilin, and also with good resin regeneration.
|
|---|
