Determination of chemical and sensory attributes of frozen and dried blueberries
Anna Consuelo De Guzman; George Srzednicki and John Craske
Proceedings of the APEC symposium on postharvest handling systems Bangkok, Thailand September 1-3, 2003. p. 211
2003
บทคัดย่อ
Determination of chemical and sensory attributes of frozen and dried blueberries
The aim of this study was to determine the effects of osmotic treatment and drying on the chemical and sensory characteristics of blueberries. Samples of frozen blueberries were thawed and divided in two sub-samples. The first sub-sample was osmotically pretreated using a sucrose + salt solution and dried in a cabinet dryer. The second sub-sample, considered as control, was dried directly in the cabinet dryer. The quality attributes were determined in thawed untreated blueberries as well as in the dried fruit. The volatile compounds in blueberry samples were isolated using Likens &Nickerson simultaneous distillation and extraction. Gas chromatography/mass spectrometry were used to identify the volatile compounds. Quantitation of the volatile compounds was carried out with an internal standard. The odour of the detected compounds was investigated using gas chromatography-olfactometry. The sugar and acid content of the blueberries were determined using HPLC. The blueberries were used to make blueberry muffins and a sensory evaluation of different sensory attributes of the muffins was carried out. A total of 51 compounds were detected in frozen-thawed blueberries as well as in the dried control samples, whereas in the sucrose + salt treated and dried berries only 47 compounds could be detected. The majority of the compounds identified in blueberries were terpenes, alcohols and aldehydes. No single compound was responsible for the characteristic aroma of blueberries, however, the oxygenated terpenoids were discovered to be important blueberry aroma compounds as they contribute the sweet, floral and fruity flavour notes. The characteristic aroma of frozen-thawed blueberries was dominated by green, leafy, sweet, fruity and floral flavour notes, while the aroma of untreated and dried blueberries and sucrose + salt treated and dried blueberries was characterised by a decrease in green, leafy flavour note and an increase in woody, burnt flavour note contributed mainly by furancarboxaldehyde. The majority of the acid in frozen-thawed blueberries, untreated dried as well as sucrose + salt treated and dried blueberry was citric acid and succinic acid, while the major sugar was fructose and glucose. Sensory evaluation of the blueberries revealed that there was no significant difference in the panelists’liking of the different sensory attributes of the muffins containing fruit of any of the three treatments i.e. frozen-thawed blueberry, untreated and dried or osmotically pretreated and dried.