Storage stability of safran (Crocus sativus L.) emulsions obtai̇ned by different methods and carriers

Saffron, due to its characteristic color and aroma, is a demanded spice despite being expensive and rare. It is thought to be important to supply it in a stabilized and readily available form considering the growing demand of consumers for ready-to-use foods. In this study, saffron samples, obtained from Iran, classified in Category-I class according to ISO standard and defined as first grade quality, were used. Extraction optimization was conducted using 3 different saffron: water ratios (0.5: 1, 1: 1 and 2: 1, w/v), 3 different temperatures (60, 70 and 80˚C) and 10 different time periods (5, 10, 20, 30, 60, 120, 180, 240, 300 and 360 min). Extracts prepared at optimum conditions was compared to the extract prepared according to standard method of ISO. There was insignificant difference (P>0.05) between two extractions in terms of coloring power. Furthermore, it was seen by the optimization study that the equivalent values that of a standard method could be achieved in shorter time periods. However, ISO method was chosen as an extraction method for following stages of the study to avoid high temperature since it is applied at room temperature, providing energy saving and recognized at globally. Ultrafiltration was applied to concentrate the saffron extracts, obtained using by method of ISO 3632-2. In this stage, parameters of filter material (PESU and Hydrosart), cut off value (1, 5 and 10 kDa), permeate: retentate ratio (60:40, 70:30 and 80:20), pressure (2 and 3 bar) and temperature (4 and 25°C) were optimized. Color compounds of saffron extracts were concentrated in best form (low h° with high C* value) as retentate by using optimum conditions determined as 1 kDa of cut off value with PESU filter at 2 bar and 4°C with the permeate: retentate ratio of 80:20. Following subsequent to ultrafiltration, single layer emulsion (water/oil) was prepared using concentrated extract (retentate). Formula of single layer emulsion was optimized by using D-optimal integrated design approach and constituents of emulsion was determined as 67% of sunflower seed oil, 6% of polyglycerol polyricinoleate (PGPR) and 27% of saffron concentrate. Single layer emulsion with optimum formula was also used in preparation of multi-layer emulsion. But ultra-filtered extract did not meet the required concentration for preparation of multi-layer emulsion. Thus, an extract with higher saffron content was prepared to use in multilayer emulsion formula. Different hydrocolloids (maltodextrin, whey protein isolate (WPI) and β-cyclodextrin (βCD)) and their ratio in the emulsion were used as independent variable in optimization of multi-layer emulsion. One inner phase of w/o emulsion was chosen as inner phase with two different outer phases as WPI- βCD complex and only βCD to prepare w/o/w multi-layer emulsion system considering color and particle size values and analyses were conducted during storage. Eventually, 7 different formulas were produced in 2 replicates and stored for 35 days at 3 different temperatures (5, 25 and 45°C). Throughout storage, analyses such as particle size (D43 and açıklık), color in model food (L*, h° and C*), encapsulation stability index (ESI), fraction of released crocin (FR%), encapsulation efficiency (EE%) were conducted every fifth day, while microscopic monitoring of particle size, crocin content and sensorial analyses were conducted in the beginning and end of storage. Color compounds of samples maintained as only saffron concentrate were significantly degraded and those samples were found to be unfavorable to color pilaf used as model food. But coloring ability of saffron concentrate in emulsion form was preserved even at high temperatures during storage. Mechanical mixers and preferred hydrocolloids were determined to be significantly efficient on emulsion stability.