Study on the physicochemical, nutritional, and phytochemical properties in five turmeric varieties

Turmeric is a member of the Zingiberaceae family, which known as a traditional medicine in Southeast Asian countries and can be used as a spice, food preservative, and colorant. The aim of the study was to determine the physicochemical, nutritional, bioactive compound and curcuminoid of five types Turmeric varieties. Five turmeric varieties were collected from Siem Reap province and were freeze-dry before studying. According to the results, the L*, a*, b*, and ΔE value of dried turmeric varieties such as BLK, BG, SN1, FG, and BRN were in the range 58.17±0.00 to 81.89±0.01, -1.46±0.01 to 6.74±0.00, -0.72±0.01 to36.48±0.01, and 14.912±0.01 to 38.12±0.01, respectively. The pH and acidity value ranged from 5.82±0.05 to 6.32±0.01, 0.36±0.01 to 0.85±0.00%, respectively. Moreover, the results of physicochemical were 1.94±0.07 to 3.60±0.22% moisture, 3.26±0.27 to 7.55±0.48% ash, 1.37±0.70 to 11.76±0.67% fiber, and 2.09±0.23 to 10.12±0.87% lipid. The higher value of TPC, TFC, TCC, and TAA were found 11.96±0.98 mg GAE/g db, 83.70±8.11 mg QE/g db, 5.6±0.05%, and 80.71±1.43%. Furthermore, the higher value of CUR, DMC, and BDMC were found in the range 1.60±0.27, 5.87±0.01, and 1.38±0.02 mg/100g db. However, only two turmeric varieties, BLK and FG, were not detected in curcuminoid.


Introduction
Turmeric is a perennial plant that is rhizomatous and herbaceous, belonging to the Zingibaraceae family [1].It is a plant distributed throughout tropical and subtropical regions of the world and mostly found in Cambodia, China, India, Thailand, Vietnam, Malaysia, Indonesia, Philippines, Australia, Africa, Peru, West Indies, and other countries [2].This spice is also the most important parts of the human diet, not only enhance the flavor, aroma, and color of food and beverages [3].More interestingly, it is not only used for food but also for medical applications such as herbs, skin care products, and cosmetics [4].Turmeric has been studied as bioactive constituents as approximately 235 compounds, primarily phenolic and terpenoid have been identified in many different species of turmeric rhizomes.More than this, around 20 to 22 diarylheptanoids and diarylpentanoids, around 8 phenylpropenes, 2 alkaloids, 4 sterols, other phenolic compounds, monoterpenes, sesquiterpenes, diterpenes, triterpenoid and many other compounds have been composed in turmeric.But in some study are identified that only curcuminoids and essential oil have been clarified as the major bioactive compound [5].The phenolic compounds has been categorized into different subgroup like phenolic acids, flavonoids, lignans, quinones, stilbene, tannins, coumarins and curcuminoids [6].Curcuminoid is the main active compound in turmeric [7] and its compound contains curcumin (70-75%), demethoxycurcumin (10-25%), and IOP Publishing doi:10.1088/1755-1315/1297/1/012009 2 bisdemethoxycurcumin (5-10%) [8].Additionally, the nutritional composition of turmeric was investigated the moisture content (76.02%), carbohydrate content (16.37%), ash content (3.04%), crude fiber (1.95%), proteins content (1.83%), and lipid content (0.80%) [9].
Due to in Cambodia have found there are many types of turmeric varieties and some of them, most people rarely know and use in diary life (yellow turmeric or Curcuma Longa L.).However, there is still lack of information about some nutritional components, including the bioactive compounds in all kind of those spices.The current objective is to determine physicochemical properties (color, moisture content, pH, and total acidity), nutritional value (ash content, fiber content, and lipid content), bioactive compounds contain total phenolic content (TPC), total flavonoid content (TFC), total curcumin content (TCC), and total antioxidant activity (TAA).The curcuminoid compounds such as curcumin (CUR), demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC) of five selected turmeric varieties by HPLC.

Sample Collection
Fresh five types turmeric rhizomes varieties such as Broteal lakai (BLK), Broteal roneang (BRN), Black ginger (BG) (scientific name: Kaemferia paviflora), Fire ginger (FG), and Sena 100 (SN1) were obtained from Kulen mountain in Siem Reap province, Cambodia.The rhizomes were harvested from a farm, packed into plastic bags, and then transported to the laboratory of the Faculty of Chemical and Food Engineering at the Institute of Technology of Cambodia for further analysis.

Freeze-drying
Turmeric was washed twice with tap water to remove dust, then peeled and washed it again to make sure all the peels was removed from turmeric sample.After that, it was sliced, packed and frozen at -20 o C for 24 h.After frozen, it was dried by freeze-dryer at -53 o C with pressure 0.04 mbar for 48 h and then kept it in vacuum plastic bag and stored at -20 o C for next analysis.

Physicochemical properties analysis
The color of the five varieties of turmeric sample were measured by using Chroma meter (CR-400, Konica Minolta).
Where, MS mass sample in aluminium cup (g), M0 mass aluminium cups after dried in oven (g), MD mass sample after dried with aluminium cup (g).
The pH value of dried turmeric varieties were measured by using pH meter and following the method AOAC 981.12 [11].The total acidity of the samples was determined by titration method (AOAC, 2012).The calculation of those parameter was following the formula below.
Where, CN is the concentration normality of solution NaOH, VNaOH is the volume of NaOH after titration (mL), EqAcetic Acid is the equivalent weight of acetic acid (60), and mS is mass sample (g)

Nutritional value analysis
Ash content of each sample were determined by heating at 550ºC for 3 hours (Wiley, 1886).
Where M0 is the mass of empty porcelain (g), M1 is the mass of sample (g) and the M2 is the mass of sample with porcelain after heating (g).
(5) Where W0 is the mass of empty plate, W1 is the mass of sample and the W2 is the mass of the plate with extract oil.
Fiber analysis in each sample were analyzed using ceramic fiber filter method (AOAC 920.169, 2012).
Where W is mass sample, W1 is mass fiber bag, W2 is mass of sample after drying in oven 105℃, W3 is mass of porcelain and W4 is mass of sample after heating at 550℃.

Bioactive compounds extraction and analysis
The five different types of turmeric varieties were extracted by ultrasonic method and used ethanol as a solvent [12].The Folin-Ciocalteu reagent was used to determinate total phenolic content (TPC) [13].The total flavonoid content (TFC) in each extract was investigated using the aluminium chloride colorimetry assay [14].The antioxidant activity (TAA) was determined by using DPPH (2,2-diphenyl-1-picrylhydrazy) radical scavenging capacity assay with the slight modifications [15].Total curcumin content (TCC) in yellow turmeric was determined by using the UV-Vis spectrophotometric method [14].
Where, C is concentration obtained from the calibration curve (μg/ml), V is volume of solution (ml), DF is dilution factor, m is mass of sample (g), and 1000 is conversion unit from μg to mg Where, C is the absorbance of the control and S is the absorbance of the sample solution ) column was used in this experiment.A reverse-phase HPLC assay was carried out using an isocratic system with a flow rate of 1 mL/min, a column temperature of 25°C, a mobile phase of 60% of Acetonitrile (CH3CN) and 40% of Acidified water (Acetic acid 1%) (40:60, v/v).The injection volume was 5 μL.The curcuminoids were detected wavelength at 425 nm.The result of percentage of curcuminoid was determined by the following formula in below.
Where, C is Concentration of curcumin that obtained from curve (mg/mL), V is Volume of ethanol (mL), DF is Dilution factor, M is Mass of dried sample (g)

Statistical analysis
In this experiment, all data were analysed by using Minitab 21 program and the data were done in triplicate that described as mean ± standard deviation (STD).The significant different between sample were analysed by using analysis of variance (One-Way ANOVA) and fisher test was the value significant difference (p < 0.05).

Physicochemical characteristics of turmeric
The physicochemical properties of fresh and freeze-dried of five turmeric varieties were analysed including color, moisture content, pH, and total acidity and the results were shown in table 1 and 2 Mean values and standard deviation (n=3).Mean with a different letter within the column indicates significant different to variety (p<0.05).
The highest value of moisture content of fresh turmeric was found in BRN (90.69 ± 3.02), while the lowest was found in BG (73.63±0.13%).The moisture content of fresh turmeric depends on the soil, climatic condition, temperature, humidity, geography, seasonal changes and the growing condition of the turmeric rhizomes which were used as the raw materials [16].After freeze drying the water was lost and the lower value was 1.94±0.07%presented in SN1.According to CAC (Codex Alimentarius Commission), the moisture content of turmeric powder was acceptable which lower than 10% in mass.
The samples BLK and BG presented statistically equal and higher pH values as compare to the other samples (p<0.05).The highest value of pH value of freeze-dried turmeric was found in BG (6.32±0.01),while the lowest value was found in FG (5.82±0.05).The last, the highest value of total acidity of freezedried turmeric was found BLK (0.85±0.00%) and the lowest value was found in BG (0.36±0.01%).Nevertheless, the presence of organic acids can cause a buffering effect during the storage, or promote the development of microorganisms, thus interfering with the pH value and acidity, and leading to a misinterpretation between the pH value and the acidity of the product [17].The values are expressed as the mean ± standard deviation (n=3).Means with different letters in the same column were significantly different (p<0.05).
The highest value of the lightness L* in fresh turmeric was found in FG (74.81±2.06),while the lowest value was found in BG (44.59±4.13)because of FG was a white turmeric and BG was a black turmeric type.In contrast with the sample of freeze-dried turmeric, the maximum L* value was obtained with BRN (81.89±0.01)and the minimum value was obtained with BG (58.17±0.00)with significant difference (p<0.05).Regarding redness/greenness, the parameter of a*, the highest value of a* value of fresh turmeric was found in BG (6.58±1.66),while the lowest value of a* value was found in BRN (-2.36±2.72).For the freeze-drying BG presented as a highest value (6.74±0.00)and BLK presented as a lowest value (-1.46±0.01).For the b* value of fresh turmeric of BLK, BG, SN1, FG, and BRN were 12.11±1.50,14.78±4.45,46.52±5.05,25.12±1.41,and 36.44±9.54,respectively.Furthermore, the color difference (ΔE) was used to quantify the potential color change in turmeric samples processed by freeze drying technique with respect to fresh turmeric and showed a significantly different ∆E value (p<0.05).The color difference (ΔE) value of BLK, BG, SN1, FG, and BRN were 38.12±0.01,20.60±0.01,22.36±0.00,14.912±0.01,and 19.57±0.01,respectively.The maximum value of ΔE was found in BLK (38.12±0.01),while the minimum value was found in FG (14.912±0.01).

Nutritional properties of turmeric
The nutritional composition of five turmeric powder were analysed including ash, fiber, and lipid content were shown in Table 3.The values are expressed as the mean ± standard deviation (n=3).Values with a different letter within the same column are significant different (p<0.05).
The highest ash content was found (7.55±0.48%) is recorded in the FG sample which is better quality or grade than the other samples, while the lowest ash content is recorded in sample BG (3.26±0.27%).The quality of turmeric powder can also be assessed by considering the ash content.The ash content of spices is the inorganic residue remaining after the organic matter has been burnt away.When a high ash figure suggests the presence of an inorganic adulterant.High values of total ash may be due to presence of carbonates, phosphates, silicates in the sample [18].
The fiber content of freeze-dried turmeric of BLK, BG, SN1, FG, BRN were 1.37±0.70,2.02±0.12,7.06±0.48,11.76±0.67,and 3.53±0.10%,respectively.The lowest value of fiber content was found in BLK (1.37±0.70%),while the highest values is FG (11.76±0.67%).The results of this study showed that FG is the only higher and the other samples are lower than the previous study reported of the fiber content (7.12 ± 0.10%) [19].
According to table 3, the result of lipid content of freeze-dried of five turmeric varieties of BLK, BG, SN1, FG, BRN were 3.73±0.36,2.09±0.23,10.12±0.87,3.06±0.24,and 4.34±0.29%,respectively.The highest value of lipid content of freeze-dried turmeric was found in SN1 (10.12±0.87%),while lowest values was found in BG (2.09±0.23%).With all the nutritional profile of five turmeric varieties, it can be said that this plant has a great future as a functional food that should be given more attention both in research as in product development.

Bioactive compound
The figure 2 showed the results of bioactive compounds including TPC, TFC, TCC, and TAA of freezedried turmeric.The BLK, BG, SN, FG, and BRN represented Broteal lakai, Black ginger, Sena 100, Fire ginger, and Broteal roneang, respectively.The highest value of the TPC was found in SN1 (11.96±0.98 mg GAE/g dried mass), while the lowest value of TPC was found in BG (2.17±0.19mg GAE/g dried mass).Furthermore, there are significantly different between the results (p<0.05).Based on these studies, it seems that the difference in TPC of turmeric obtained by ethanol extraction might be due to the amount of active substances, extraction time, temperature and geographic area of cultivation of turmeric [20].
The TFC in turmeric varieties illustrated that BLK, BG, and SN1 were significantly different (p<0.05) but FG and BRN were not significantly different (p>0.05).The maximum value of the flavonoid content of freeze-dried turmeric of ethanol extract was found in SN1 (83.70±8.11mg QE/g dried mass).The minimum value of TFC of freeze-dried turmeric was found in BG (8.60±0.39mg QE/g dried mass).turmeric is a good source of natural flavonoids, which have been shown to have antioxidant activity, free radical-scavenging capacity, coronary heart disease preventive activities, and anticancer activities [21].different between the results (p<0.05).The highest value of TCC of freeze-dried turmeric was found in BLK (5.6±0.05%) and the lowest value of TCC of freeze-dried turmeric was found in FG (1.8±0.02%).
The results of this study are highly consistent with their work.Curcumin is a prominent component in turmeric rhizome and its content directly effects on determining the color of turmeric.The turmeric types with a high curcumin content appears in bright yellow color while the turmeric with a low curcumin content appears in Orange yellow color [22].
The last one shows about the value of TAA of freeze dried of five turmeric varieties.The highest value of TAA of freeze-dried turmeric was found in FG (80.71±1.43%),while the lowest value of TAA of freeze-dried turmeric was found in BG (37.08±6.39%).Furthermore, the results of BLK, SN1, and FG are no significantly different between (p>0.05).According to this study showed that the ethanol extracts exhibited the best antioxidant activity compared to the other solvents.This can be attributed to the high concentration in phenolic antioxidants.It has been demonstrated that phenolic antioxidants have the ability to donate their atoms for the stabilization of free radicals generated by the oxidative stress or to reduce and chelate transition metals that facilitate the generation of these radicals [23].

Curcuminoid content by HPLC
The amounts of curcuminoids compounds were expressed as mg per 100 g dried turmeric (mg/100g dried mass) values are shown in Table 4. Value presented as mean ± standard deviation (n=3) means with different letters in the same row were significantly different (p<0.05).ND = not detected.CUR, DMC, and BDMC represented curcumin, demethoxycurcumin, and bisdemethoxycurcumin, accordingly.
The highest value of CUR of freeze dried of five turmeric varieties was found in BG (1.60±0.27mg/100g), and the lowest value of CUR was found in BRN (0.48±0.00 mg/100g dried mass).Curcumin was found to be the major compound in all of the tested turmeric samples.For bisdemethoxycurcumin compound of freeze dried of five turmeric varieties showed that BG, SN1, and BRN were 0.56±0.02,0.85±0.00,and 0.40±0.02mg/100g dried mass, respectively.The highest value of BDMC of freezedried turmeric was found in SN1 (0.85±0.00 mg/100g dried mass), and the lowest value of BDMC of freeze-dried turmeric was found in BRN (0.40±0.02 mg/100g dried mass).The results can be seen that differences in turmeric varieties cause significant differences (p<0.05) in the CUR and DMC content.But, on the other hand, it did not show significant difference (p>0.05) to the BDMC component.

Conclusion
In conclusion, the results of the study on freeze-dried of five turmeric varieties were showed that the parameter of color such as L*, a*, b,* and ∆E to be in BRN (81.89±0.01),BG (6.74±0.00),BLK (36.48±0.01),and BLK (38.12±0.01),respectively.The values of moisture content, pH, total acidity, ash content, fiber content, and lipid content varied between (1.94±0.07 to 3.60±0.22%),(5.82±0.05 to 6.32±0.01),(0.36±0.01 to 0.85±0.00%),(3.26±0.27 to (7.55±0.48%),(1.37±0.70 to 11.76±0.67%),(2.09±0.23 to 10.12±0.87%),respectively.The highest values of bioactive compounds of freeze dried of five turmeric varieties including TPC, TFC, TCC, and TAA were found in SN1, BLK, and FG with 11.96±0.98mg GAE/g, 83.70±8.11mg QE/g, 5.6±0.05%,80.71±1.43%respectively.SN1 was found the greatest amounts of curcuminoid compounds such as CUR, DMC, and BDMC with 0.79±0.00,5.87±0.01,0.85±0.00mg/100g dried mass, respectively.Curcumin was found to be the major compound in all of turmeric samples while BLK, and FG were not detected (ND).However, all these studied parameters considering as a document about physicochemical, nutritional composition, bioactive compound, and curcuminoids of five turmeric varieties of Cambodia that can be used for the reference for the future research.Further research should be done to determine essential oil, protein content, carbohydrate, vitamin, and mineral due to the present study lack of the equipment and time to constrain.It is also important to consider these parameters for the next study.

Table 1 .
. The physicochemical properties of five turmeric varieties.

Table 2 .
The color value L*, a*, b* of fresh and freeze-dried of five turmeric varieties

Table 3 .
The nutritional properties of freeze-dried of five turmeric

Table 4 .
Curcuminoids in freeze-dried of five turmeric varieties.