Introduction: Ficus carica, commonly known as fig, is among the oldest types of fruit known to mankind. Drying is defined as a thermal process under controlled conditions in order to reduce the moisture in different types of food via evaporation. Edible films and coatings are used to enhance food quality by precluding oxidation and color changes in inappropriate conditions. Carboxymethyl cellulose (CMC) is thus widely used to improve food shelf life.
Materials and methods: All experiments were carried out on fresh edible green variety figs planted in the county of Neyriz Estahban. The figs were then immersed in the following solutions:
Distilled water as a control variable without coating; carboxy methyl cellulose (CMC) solution 1% containing 0.25 gr/L glycerol; and CMC solution 1% containing 0.25 gr/L glycerol and 2% ascorbic acid. Preliminary tests including average diameter, pH, total flavonoids content, and antioxidant activity were performed on the figs. The fruits were dried using a device designed by the authors. At 60 ̊C, 70 ̊C, and 80 ̊C, the airflow in the device was 0.5 m/s, 1.0 m/s, and 1.5 m/s, respectively. After drying the samples, secondary experiments were performed which, in addition to the previous tests, included texture analysis, water reabsorption, volume measurement, shrinkage, and color analysis. A total of 27 treatments were applied in 3 rounds. A full factorial design was employed for statistical analyses while average values were compared via Duncan’s test at 5% significance. Calculations were performed using SPSS 16.0.
Results & Discussion: Using CMC coating, shrinkage increased compared to the control sample. As airflow accelerates from 0.5 m/s to 1.5 m/s, higher levels of shrinkage are observed. This could be attributed to the drier surface of the fruit caused by faster airflow. Shrinkage increases with the speed of airflow going from 0.5 m/s to 1.5 m/s. This is because at higher speeds, the sample is dried in a shorter period of time and sustains less damage.
Water reabsorption was found to decrease with higher temperature and airflow. Weak reabsorption results from the breakdown of the internal structure of the fruits.
CMC-ascorbic acid, CMC, and the control sample had the highest to lowest levels of firmness, respectively. The acid was found to preserve the internal cellular structure and preserve its breakdown. Moreover, firmness increases with the drying temperature.
According to the results, the samples coated with CMC and CMC-ascorbic acid had lower pH compared to the control sample. Airflow speed and temperature are inversely and directly related to pH, respectively.
In the CMC-ascorbic acid treatment, antioxidant capacity increased compared to the other two treatments. This may be associated with ascorbic acid’s higher ability to act as a carrier of anti-browning agents. Also, higher levels of antioxidant behavior were observed with higher temperature as it causes faster drying. Moreover, the coating acts to preserve the antioxidant and eliminates the impact of temperature.
The highest amount of flavonoids was observed in the CMC-ascorbic acid treatment followed by the control sample and the CMC treatment. This is because the ascorbic acid serves to maintain the flavonoids in the samples. The flavonoid content increases with the airflow speed since the sample is dried in a shorter duration and the flavonoids are preserved. However, higher temperature reduces the flavonoid content since heat damages the pigment.
The application of the CMC coating (alone or in combination with ascorbic acid) increased luminance compared to the control sample due to the preventative effect of the edible coating on the oxidation of the pigments in the fig samples. With faster airflows, surface moisture begins to vary which causes the coating to become lighter with higher L*. An increase in the temperature leads to lower L* as the heat causes the carotenoids and chlorophyll to break down and form brown pigments in the samples.
Using the CMC-ascorbic acid coating increases a* in figs. Furthermore, as the temperature goes up from 60 ̊C, a* also increases.
The coated samples demonstrate higher levels of b* compared to the control sample. In fact, the coating preserves the pigments and thus maintains the yellow color of the figs. The value of b* is directly related to the speed of the airflow because it decreases drying time. As a result, the product undergoes less heat. Finally, higher temperature leads to higher b* in the dried figs. |
- ایوبی، ا.، صداقت، ن.، کاشانی نژاد، م.، محبی م.، نصیری محلاتی، م.، 1393، مقایسه اثر پیشتیمارهای غیرشیمیایی و شیمیایی بر ویژگیهای کیفی کشمش، اولین همایش ملی میان وعدههای غذایی، ایران، مشهد مقدس، پژوهشکده علوم و فناوری مواد غذایی، اردیبهشت ماه 93.
- طهماسبیپور، م.، دهقاننیا، ج.، سیدلوهریس، ص.، قنبرزاده، ب.، 1392، مدلسازی تغییرات رنگی طی خشک کردن انگور پیشتیمار شده با فراصوت و کربوکسی متیل سلولز و بررسی ویژگیهای حسی آن، فصلنامه علوم و فناوریهای نوین غذایی، 79-61: 4.
- غلامی پرشکوهی، م.، رشیدی، م.، رنجبر، ا.، عباسی، س.، 1389، تاثیر دما، سرعت جابه جایی هوا و روش آماده-سازی بر خواص کیفی کشمش حاصله از انگور بیدانه سفید، مجله علوم غذایی و تغذیه، 63-54: 3.
- Baini, R., Langrish, TAG., 2009, Assessment of colour development in dried bananas–measurements and implications for modelling, Journal of food engineering, 93(2): 177-182.
- Carcel, JA., Garcia-Perez, JV., Sanjuan, N., Mulet, A., 2010, Influence of pre-treatment and storage temperature on the evolution of the colour of dried persimmon. LWT-Food Science and Technology, 43(8): 1191-1196.
- Carneiro-da-Cunha, MG., Cerqueira, MA., Souza, BWS., Souza, MP., Teixeira, JA., Vicente, AA., 2009, Physical properties of edible coatings and films made with a polysaccharide from Anacardium occidentale L, Journal of Food Engineering, 95(3): 379-385.
- Doymaz, I., 2004, Effect of pre-treatments using potassium metabisulphide and alkaline ethyl oleate on the drying kinetics of apricots, Biosystems Engineering, 89(3): 281-287.
- Doymaz, I., Pala, M., 2002, The effects of dipping pretreatments on air-drying rates of the seedless grapes, Journal of Food Engineering, 52(4): 413-417.
- Koushesh Saba, M., Sogvar, OB., 2016, Combination of carboxymethyl cellulose-based coatings with calcium and ascorbic acid impacts in browning and quality of fresh-cut apples, LWT - Food Science and Technology, 66: 165-171.
- Marpudi, S.L., Ramachandran, P., Srividya, N., 2013, Aloe vera Gel Coating For Post Harvest Quality Maintenance of Fresh Fig Fruits, Research Journal of Pharmaceutical, Biological and Chemical Sciences, 4: 878-887.
- Maskan, M., 2001, Kinetics of colour change of kiwifruits during hot air and microwave drying, Journal of Food Engineering, 48: 169-175.
- Mellema, M., 2003, Mechanism and reduction of fat uptake in deep-fat fried foods, Trends in food science & technology, 14(9): 364-373.
- Oms-Oliu, G., Soliva-Fortuny, R., Martin-Belloso, O., 2008, Edible coatings with antibrowning agents to maintain sensory quality and antioxidant properties of fresh-cut pears, Postharvest Biology and Technology, 50: 87-94.
- Pedro, AC., Granato, D., Rosso, ND., 2016, Extraction of anthocyanins and polyphenols from black rice (Oryza sativa L.) by modeling and assessing their reversibility and stability, Food Chemistry, 191: 12-20.
- Perez-Gago, MB., Serra, M., Del, RMA., 2006, Color change of fresh-cut apples coated with whey protein concentrate-based edible coatings, Postharvest Biology and Technology, 39: 84–92.
- Robles Sanchez, RM., Rojas Graü, MA., Odriozola Serrano, I., Gonzalez Aguilar, G., Martin Belloso, O., 2013, Influence of alginate-based edible coating as carrier of antibrowning agents on bioactive compounds and antioxidant activity in fresh-cut Kent mangoes, LWT - Food Science and Technology, 50: 240-246.
- Toğrul İT., 2010, Modelling of heat and moisture transport during drying black grapes, International journal of food science & technology, 45(6): 1146-1152.
- Trichopoulou A., Vasilopoulou, E., Georga, K., Soukara, S., Dilis, V., 2006, Traditional foods: Why and how to sustain them. Trends in Food Science & Technology, 17(9): 498-504.
- Xanthopoulos, G., Yanniotis, S., Lambrinos, G., 2010, Study of the drying behaviour in peeled and unpeeled whole figs, Journal of Food Engineering, 97(3): 419-424.
- Xiao, H-W., Pang, C-L., Wang, L-H., Bai, J-W., Yang, W-X., Gao, Z-J., 2010, Drying kinetics and quality of Monukka seedless grapes dried in an air-impingement jet dryer, Biosystems Engineering, 105(2): 233-240.
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