Faculty of Biotechnology, Ho Chi Minh City Open University, Ho Chi Minh City, Vietnam
Corresponding author email: minh.np@ou.edu.vn
Article Publishing History
Received: 09/02/2020
Accepted After Revision: 25/03/2020
Chestnut (Castanea sativa) is a gluten-free seasonal nut. Chestnut has become important composition for human diet owing to their demonstrated nutritional qualities and healthy benefits. Its seed has radical scavenging activity with a rich source of natural antioxidants for different applications. It contains various alkaloids, flavonoids, volatile oils and terpenoids essential for variety of antimicrobial, antitumor, antioxidant activities. Owing to the healthy constituents in chestnut seed, there is a potential supplement for human meal. Drying and roasting are very important in enhancing color, flavor, appearance and taste in seeds. There was not many research related to the change of antioxidant during hot air drying as well as storage. So purpose of this study was to examine the effectiveness of thermal treatment in hot air drying, roasting, packaging and storage to vitamin C and total phenolic in the dried chestnut (Castanea sativa) seeds. Results revealed that drying temperature (45 oC), roasting (135 oC in 10 min), packing in polyethylene bag and keeping in dry cool place were suitable to preserve the vitamin C, total phenolic contents in the samples for 12 months. The drying, roasting temperature and duration were thoroughly identified to manufacture the dried roasted chestnut seeds.
Chestnut, Drying, Roasting, Preservation, Vitamin C, Phenolic
Nguyen M. P. Ascorbic Acid and Total Phenolic Contents of Dried Roasted Chestnut (Castanea sativa) Affected by Drying, Roasting and Preservation. Biosc.Biotech.Res.Comm. 2020;13(1).
Nguyen M. P. Ascorbic Acid and Total Phenolic Contents of Dried Roasted Chestnut (Castanea sativa) Affected by Drying, Roasting and Preservation. Biosc.Biotech.Res.Comm. 2020;13(1). Available from: https://bit.ly/3cpAej9
INTRODUCTION
Chestnut (Castanea sativa Mill) belongs to the family Fagaceae. This nut has a smooth and coriaceous epicarp, which can be light brown or deep brown in colour with more or less evident stripes, (Kosnovska,2013). It’s nutritionally rich with high content of sugar, starch, dietary fibre, high quality protein, low lipids, rich in vitamins and minerals, good source of fatty acids and antioxidants (Chenlo F. et al., 2007; Borges et al., 2007; Kunsch et al., 1999; Vasconcelos et al., 2007). There were several studies mentioned to processing of chestnut. Effects of roasting on chemical composition and quality of different chestnut (Castanea sativa Mill) varieties were examined ( Kunsch et al., 2001). The total vitamin C content and antioxidant activity of raw and cooked chestnuts was evaluated. The cooking process significantly changed the antioxidant activity of the chestnuts. A significant decrease in the vitamin C content of the chestnuts was observed (Barros et al., 2011). The effects of pan and microwave roasting on physicochemical, functional, rheological and antioxidant properties of sweet chestnut were compared. Roasting increased the water absorption capacity and oil absorption capacity of chestnut flours making them potentially useful in flavor retention and improvement of palatability. Roasted flours had higher TPC and antioxidant activity. The gelatinization temperatures were higher in roasted flours while as their viscoelastic behavior was lower as compared to the native flour. Roasting also improved the flavor of chestnuts with microwave roasted chestnuts expressing better aroma as compared to the pan roasted (Wani et al., 2017). The effect of hot air convective drying on the organic acid profile of chestnut was evaluated ( Delgado et al., 2018).
Most studies conducted on hot air drying of chestnuts have examined various technological varibale such as chemical parameters (Correia, et al., 2009, 2012; Moreira et al., 2013; Zhang et al., 2011), temperature effect on morphological and rheological attributes of chestnut flours, rehydration effect (Attanasio et al., 2004; Moreira et al., 2008; Moreira et al., 2011), energetic requirements (Koyuncu et al., 2004), drying kinetics (Cletus et al., 2008; Delgado et al., 2014; Guiné et al., 2006; Moreira et al., 2005). Purpose of the this study was to identify the efficacy of thermal treatment in hot air drying, roasting, packaging and preservation to vitamin C, total phenolic in the dried Chestnut (Castanea sativa) seed.
MATERIAL AND METHODS
Materials: Chestnut, Castanea sativa was collected from Tien Giang province, Vietnam. They were cultivated following VietGAP without using pesticide or insecticide to ensure food safety. After collecting, harvested seeds were preserved at dry cool place and conveyed to laboratory as soon as possible for experiments. These seeds were cleaned thoroughly by air blowing to remove foreign matters. The seeds were sorted to get the uniformity and defect-free ones. Before roasting treatment, chestnut kernels were submersed in 15% (w/w) salt solution for 30 min. Then, the draining water of sieved seeds was removed. Apart from chestnut, Castanea sativa, we also used other materials during the research such as NaCl, HCl, Na2CO3, Folin-Ciocalteau. Lab utensils and equipment included weight balance, hot air dryer and spectrophotometer.
Phytochemical constituents inside fresh Chestnut (Castanea sativa) seed: The phytochemical constituents such as protein (%), fat (%), moisture (%), vitamin C (mg/g), total phenolic (mg/g) in fresh Chestnut (Castanea sativa) were measured as follows: Protein (by Kjeldahll), fat (by Soxhlet) and moisture (drying to constant weight) were used. Vitamin C (mg/g) were performed by a validated hydrophilic interaction chromatography method (Barros et al., 2010). Total phenolic (mg/g) was determined colorimetrically using Folin- Ciocalteau reagent by spectrophotometer.
Efficacy of hot air drying temperature to vitamin C, total phenolic in dried Castanea sativa seed: In order to examine the efficacy of hot air drying temperature to the dried Chestnut (Castanea sativa) seed, the vitamin C, total phenolic were measured before and after drying in different hot air drying temperature (35 oC, 40 oC, 45 oC, 50oC).
Efficacy of roasting conditions on vitamin C, total phenolic in the dried Chestnut (Castanea sativa) seed: At the end of drying treatment, the dried seeds were roasted at different conditions (130 oC for 15 min, 135 oC for 10 min, and 140 oC for 5 minutes). The vitamin C (mg/g), total phenolic (mg/g) were analyzed to determine the optimal roasting condition.
Efficacy of storage temperature to vitamin C, total phenolic in dried Chestnut (Castanea sativa) seed
The dried Chestnut (Castanea sativa) seeds were preserved in PA bag in 4oC, 30oC. The vitamin C (mg/g), total phenolic (mg/g) were monitored in 3 month-interval for 12 months.
Statistical analysis: All experiments were run in triplicate with three different lots of samples. Statistical analysis was performed by the Statgraphics Centurion XVI.
RESULTS AND DISCUSSION
Phytochemical constituents in raw Chestnut (Castanea sativa). The phytochemical constituents in raw Chestnut (Castanea sativa) seed were analyzed. The present results revealed that raw chestnut seed has high content of vitamin C and total phenolic (Table 1).
Table 1. The phytochemical constituents in raw Chestnut (Castanea sativa) seed
| Variables | Protein (%) | Fat (%) | Moisture (%) | Vitamin C (mg/g) | Total phenolic (mg/g) |
| Value | 24.76±0.01 | 6.25±0.00 | 57.38±0.03 | 12.63±0.01 | 49.28±0.00 |
Note: the values were expressed as the mean of three repetitions; the same characters (denoted above), the difference between them was not significant (α = 5%).
Efficacy of hot air drying temperature to vitamin C, total phenolic contents in dried Chestnut seeds:
Convective drying depended on different variables such as temperature, relative humidity and velocity of the drying air; size, shape and loading density of the samples (Moreira et al., 2015). In order to examine the efficacy of hot air drying temperature to the dried Chestnut (Castanea sativa) seed, the vitamin C, total phenolic was measured before and after drying in different hot air drying temperature (35 oC, 40 oC, 45 oC, 50oC). From table 2, the Chestnut (Castanea sativa) was dried at 45oC to preserve the highest amount of vitamin C (mg/g), total phenolic (mg/g). In another report, the thermal process at 50ºC caused equivalent losses of ascorbic acid ( Delgado et al., 2018). Roasting, boiling and frying procedures lead to significant reduction of total organic acids contents (Barbara Ribeiro et al., 2007). Fresh chopped chestnuts were dried using a hot air convective tray dryer at different temperatures (45, 65 and 85ºC) and loading densities (2.5 and 6.3 kg/m2). Total and damaged starch varied significantly with drying temperature and loading density (Moreira et al., 2015).
Table 2. Vitamin C (mg/g), total phenolic (mg/g) in dried Chestnut (Castanea sativa) seed by the effect of hot air drying temperature (oC)
| Parameter | Raw Chestnut (Castanea sativa)
before drying |
Dried Chestnut (Castanea sativa) seed by the effect of hot air at drying temperature (oC) | |||
| 35 | 40 | 45 | 50 | ||
| Vitamin C (mg/g) | 12.63±0.01a | 9.37±0.00b | 9.13±0.02bc | 9.04±0.00bc | 8.35±0.00c |
| Total phenolic (mg/g) | 49.28±0.00a | 31.53±0.01b | 31.05±0.02bc | 30.48±0.01bc | 29.74±0.02c |
Note: the values were expressed as the mean of three repetitions; the same characters (denoted above), the difference between them was not significant (α = 5%).
Efficacy of roasting conditions on vitamin C, total phenolic in the dried Chestnut (Castanea sativa) seed:
Chestnut has the high proportion of tannins in the inner shell. Tannins are known for their astringent bitter taste that reduce the palatability. Roasting before their utilization is a normal handling to enhance the color and flavor. The thermal treatment received during roasting changes the nutritional compositions of chestnuts by increasing the antioxidant activity and reducing the anti-nutritional factors such as tannins (Chang et al., 2016). In this process, the nuts are heated applying the conventional thermal treatment, such as air convection and pan or sand roasting at 250–300°C for a short time ( Demir et al., 2002; 2005;Schlörmann et al., 2015; Sharma et al., 2011).
In this research, at the end of drying treatment, the dried seeds were roasted at different conditions (130 oC for 15 min, 135 oC for 10 min, and 140 oC for 5 minutes). The vitamin C, total phenolic were analyzed to determine the optimal roasting condition. Results were elaborated in table 3. Chestnut (Castanea sativa) seed must be roasted at 135 oC for 10 min to preserve vitamin C (mg/g), total phenolic (mg/g) at the highest level. In another research, the effects of roasting on starch, sugars and fatty acid composition and on chestnut quality were verified. Weight loss of chestnut by roasting from 23-30% while causing little change in composition ( Kunsch et al., 2001). Roasting reduced the anti-nutritional factors in chestnut. Protein, fat, and ash contents displayed insignificant variation upon roasting. Significant increase in water absorption capacity, oil absorption capacity, and antioxidant properties was observed following roasting. Flour obtained from roasted chestnuts exhibited a significant decrease in light transmittance, foaming, and pasting properties. Higher gelatinization temperatures and lower enthalpies were reported in microwave and pan roasted chestnut flours. Roasting also reduced the viscoelastic behavior of native sweet chestnut and changed the transmittance of identical functional groups (Wani et al., 2017).
Table 3. Efficacy of roasting conditions on vitamin C (mg/g), total phenolic contents (mg/g) in the roasted dried Chestnut (Castanea sativa) seed
| Roasting conditions | 130 oC for 15 min | 135 oC for 10 min | 140 oC for 5 min |
| Vitamin C (mg/g) | 7.15±0.03ab | 7.94±0.00a | 6.84±0.03b |
| Total phenolic (mg/g) | 26.49±0.00ab | 27.81±0.02a | 25.70±0.00b |
Note: the values were expressed as the mean of three repetitions; the same characters (denoted above), the difference between them was not significant (α = 5%).
Efficacy of storage temperature to vitamin C, total phenolic in dried Chestnut (Castanea sativa) seed. Roasting also improved the digestibility and stability of chestnut (Wani et al., 2017). The dried Chestnut (Castanea sativa) seeds were preserved in PA bag in 4oC, 30oC. The vitamin C, total phenolic were monitored in 3 month-interval for 12 months. From table 4, the roasted dried Chestnut (Castanea sativa) seed must be stored in PA (vaccum) bag in dry cool place so that the vitamin C (mg/g), total phenolic (mg/g) could be preserved for 12 months.
Table 4. Vitamin C (mg/g), total phenolic (mg/g) in dried Chestnut (Castanea sativa) seed by the effect of storage temperature
| Storage duration (months) | Dried Chestnut (Castanea sativa) seed stored in PA bag at 4oC | Dried Chestnut (Castanea sativa) seed stored in PA bag at 30oC | ||
| Vitamin C (mg/g) | Total phenolic
(mg/g) |
Vitamin C
(mg/g) |
Total phenolic
(mg/g) |
|
| 0 | 7.94±0.00a | 27.81±0.02a | 7.94±0.00a | 27.81±0.02a |
| 3 | 7.83±0.02ab | 27.24±0.03ab | 7.74±0.03ab | 27.19±0.00ab |
| 6 | 7.59±0.03b | 27.03±0.00b | 7.50±0.03b | 26.95±0.01b |
| 9 | 7.48±0.00bc | 26.86±0.02bc | 7.39±0.01bc | 26.77±0.01bc |
| 12 | 7.39±0.01c | 26.50±0.01c | 7.31±0.02c | 26.39±0.03c |
Note: the values were expressed as the mean of three repetitions; the same characters (denoted above), the difference between them was not significant (α = 5%).
CONCLUSION
Antioxidants are valuable phytochemical elements contributing to our health benefits. Owing to the high antioxidant capacity as well as a rich source of vitamins, Castanea sativa seeds were demonstrated to prevent degenerative diseases associated with free radical damage. Drying and roasting are very important steps showing significant alterations in the manufacturing of value-added nuts with better taste, aroma, texture, crispiness. Especially, roasting can improve color and aroma through caramelization on the surface of the dried chestnut.
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