Investigation of changes in physico-mechanical properties of walnut noughl during storage time: Studying of additives' effect

Noughl (sugar coated almond or walnut) is a traditional confectionary sugar-based product which is also produced by addition of spices and dried damask rose in recent years. In spite of its popularity, noughl suffers from dehydration in a short time after being exited from the package. Thereupon, the aim of the present study was to investigate the additives' impact (cinnamon, damask rose and saffron) on physico-mechanical properties (moisture content, texture, surface area, color and aw) of noughls and also the trend of moisture loss during storage. The results indicated that the most moisture loss took place at the first 3 days after opening the package. Based on the rheological tests, the highest and the lowest breakage energy belonged to damask rose (35.48 N.mm) and cinnamon (9.1 N.mm) noughls, respectively. Besides, it was found that storing for 14 days led to increase of vanilla noughl firmness for more than three times. Moreover, mean value of water activity of noughls was lower than 0.56. Comparison of mean value of the color total difference (ΔE*) at 0 and 21st days declared that cinnamon and vanilla noughls had the highest and the lowest color alteration, respectively. According to image processing analyses, suitable indicators to show color changes during time were a* and L* channels for cinnamon and damask rose noughls and b* and L* channels for saffron and vanilla noughls.