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Journal of Human Nutrition & Food Science

Cite this article: Al-Farisi MA, Lee CY (2014) Enrichment of Date Paste. J Hum Nutr Food Sci 2(3): 1032.

*Corresponding authorAl-Farisi MA, Food Research Section, R&D, Abu Dhabi Food Control Authority, P O Box 52150, AD, UAE, Tel: +971 2 4954000; Email:

Submitted: 04 January 2014

Accepted: 27 March 2014

Published: 31 March 2014

ISSN: 2333-6706

Copyright© 2014 Al-Farisi et al.

OPEN ACCESS

Research Article

Enrichment of Date PasteAl-Farisi MA1* and Lee CY2

1Food Research Section, R&D, Abu Dhabi Food Control Authority, UAE2Department of Food Science and Technology, Cornell University, USA

INTRODUCTIONDates are popular fruit among the population of the Middle

Eastern countries, providing a staple food for millions of people in the world. The world production of dates has increased from about 4.6 million tons in 1994 to 7.9 million tons in 2010 (FAO [1]). Date paste, pitted and minced dates, is a fast growing popular date product in United Arab Emirates. The technical aspect of making date paste is simple and is normally done in date packing units which distributed around the country. It’s mainly consumed as paste, but also it’s used as a major ingredient in bakery and confectionery industries for cookies, sweet breads, candy bars. The firmness (softness) of the date paste is mainly determined by moisture content and date varieties. One of the main problems facing date paste is tending to get harder during storage and hydration by steaming or soaking of date paste which also increases risk of browning and fermentation [2].

Dates composed of a fleshy pericarp and seed which constitutes between 8 and 15% of date fruit weight [3]. The date seeds considered a waste product of many date processing plants producing pitted dates, date syrup and date confectionery. At present, seeds are used mainly for animal feeds for cattle, sheep and camel. Thus, utilization of such waste is very important to date cultivation and to increase income for this sector. Date seeds contained higher amount of protein, fat and dietary fibre compare to date flesh, as reported by Besbes & Blecker [4], Aldhaheri et al [5], Hamada et al [6], Sawaya et al [7], Al-Farsi et al [3], Al-Farsi & Lee [8]. Their reported composition for seeds were 3.1- 7.1% moisture, 2.3-6.4% protein, 5.0-13.2 fat, 0.9-1.8%

ash and 22.5-80.2% dietary fibre. The high content of dietary fiber in date seeds has important therapeutic implications for certain conditions, such as diabetes, hyperlipidemia, and obesity, and may have a protective effect against hypertension, coronary heart disease, high cholesterol, prostate cancers, and intestinal disorders [9].

Also, date seeds contain high levels of phenolics (3102-4430mg/100g) and antioxidants (580-929 µm trolox equivalents/g) as reported by Al-Farsi et al [3] Phenolic compounds of fruit seeds, such as phenolic acids and flavonoids, have been shown to possess many beneficial effects, including antioxidant, anticarcinogenic, antimicrobial, antimutagenic, and anti-inflammatory activities, and the reduction of cardiovascular disease [10]. Thus, it is important to increase antioxidant intakes in human diet, and one way of achieving this is by enriching food with natural phenolics. As some synthetic antioxidants may exhibit toxicity, have high manufacturing costs and have lower efficiency than natural antioxidants [11].

Since a large quantity of date seeds is being produced as a by-product of the date processing, and seeds contain a significant amount of bioactive phenolics and dietary fiber, the aims of this study were to utilize date seeds to produce enriched date paste high in diteray fiber and antioxidants, and improve the firmness of date paste.

MATERIALS AND METHODSChemicals

All chemicals were obtained from Sigma-Aldrich-Fluka Co. Ltd. (St. Louis, MO, USA) unless otherwise specified.

Abstract

Date paste, is a fast growing popular date’s product in the United Arab Emirates. It’s mainly consumed as paste, but also used as a major ingredient in bakery and confectionery industries for cookies, sweet breads, candy bars. One of the main problems facing date paste is tending to get harder during storage. While date seeds considered a waste product of many date processing plants producing pitted dates, date syrup and date confectionery, although it contains higher amount of dietary fiber and antioxidants compare to date flesh. Thus, utilization of such waste to improve the quality of date paste is important to the date consumption and cultivation. This study aimed to enrich date paste with seed poweder to increse dietary fiber and antioxidants, to improve firmness, and to utilize date seed. Dried and roasted seed powders were used in 3, 6 and 9% to formulate different products of dates paste. The quality of date paste enriched with date seed powder was evaluated by measuring proximate content, dietary fiber, phenolics and antioxidants. Sensory evaluation was conducted to study consumer preferences. We found that enriched date paste with 3% dry seed powder was the best formulation that showed improved firmness, dietary fiber content, antioxidant activity and sensory quality of the product.

Keywords•Date paste•Seed•Dietaryfiber•Phenolics•Antioxidants•Sensory evaluation

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Dates sample

The date of Khalas used in this study was procured from Al Foah Company, Al Ain, UAE. Figure 1 shows flow diagram for the enrichment process of date paste. Dates were washed and removed seeds manually. The seeds were oven dried for 2 days at 50°C and part of it roasted in an electric oven at 200°C for 60 min. (Thelco Precision, Jovan Inc.,Wincester, VA, USA). The seeds were then finely ground to 0.5 mm using a hammer mill (W4SS, Buffalo, NY, USA) and Stone mill (Fryma 95 stone mill, Rheinfelden, NY, USA). Dates flesh was chopped to 0.5-1.0 cm using a shredder (Urschel Laboratories Inc, Valparaiso, Indiana, USA) and mixed with seed powder in different ratios (3, 6 and 9%) by using a steamed-mincer (US Berkel 2877, Laporte, Indiana, USA). The enriched date paste pressed to square shape by hands, packed in high density polyethylene bags, heat-sealed and stored at ambient temperature until analyzed.

Proximate analysis

Percentages of moisture by vacuum oven (method 934.06), protein content by Kjeldahl nitrogen (method 920.152), and ash by direct analysis (method 940.26) were determined according to the Association of Official Analytical Chemists methods [12]. The Bligh and Dyer method [13] was used to determine the lipid content and water activity was measured using AW SPRINT (Novasina, Swiss made) instrument.

Dietary fiber

Dietary fiber content was determined by Neutral Detergent

Fiber method using ANKOM Fiber Analyzer A200. All samples were dried in a forced-air oven (55°C for 24 h) and ground to pass through a 1-mm screen of a cutter mill before analysis. Extraction of neutral detergent fiber was based on an in-house procedure using a fiber analyzer (Ankom220, Ankom Technology Corp. NY, USA). Briefly, 2 L of neutral detergent, 20 g of sodium sulfite and 4 ml of alpha-amylase were poured into the extraction chamber. Filter bags (F57, 25 µm, Ankom Technology Corp. NY, USA) containing 0.5 g of the test sample were placed in plastic trays. After inserting the plastic trays, the chamber lid was sealed, and the solution was heated to 100°C within 15 min. After 60 min of extraction (75 min total times) the detergent was expelled. Filter bags were washed three times within the chamber with 2 L of water at 80-90°C and 4 ml alpha-amylase. All washes were performed for 5 min each time with the chamber lid sealed and heat and stirrer turned on. After the last water wash, extracted filter bags were removed from the chamber and placed between two absorbent pads, and gently pressed to remove water. Filter bags were placed in a 500mL beaker, and approximately 250mL of acetone was added and soaked for 5 min. Filter bags removed from acetone and allowed to evaporate (air-drying) and bags were then dried in forced-air oven at 102°C for at least 4 h before being weighed.

Total phenolic

The total phenolic content of samples was extracted according to Al-Farsi et al. [3], they found 50% acetone (containing 7% cyclodextrin) yielded high recovery of total phenolics from dates, among seven other solvents. The Folin-Ciocalteu method [14] was used to measure phenolics with some modifications. Briefly, one ml of sample extract was mixed with 1 ml of Folin-Ciocalteu phenol reagent and allowed to react for 5 min. Then, 10 ml of 7% sodium carbonate solution (w/v) were added, and the final volume was made up to 25 ml with deionised water. After 1 h of reaction at room temperature, the absorbance at 750 nm was measured using a Spectrophotometer (Electron Corporation, Cambridge, England). Measurements were calibrated to a standard curve of prepared ferulic acid solution, as ferulic acid is the major phenolic acids in Khalas dates [3]. The total phenolic concentration was expressed as milligrams of ferulic acid equivalents per 100 g of sample on a wet weight basis.

Total antioxidant activity

The total antioxidant activity was extracted according to Al-Farsi et al [3], they found phosphate buffer (75 mM, pH 7.4) was the best solvent for extracting antioxidants from dates. Antioxidants Assay Kit (Sigma-Aldrich, CS0790, USA) was used to measure the total antioxidants. The principle of the assay is formation of a ferryl myoglobin radical from metmyoglobin and hydrogen peroxide, which oxidizes the ABTS (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) to produce a radical cation ABTS•+, a soluble chromogen that is green in color and can be determined spectrophotometrically at 405 nm. This assay been selected to measure the antioxidants in our samples due to its reliability, validity and the controlled condition provided. Briefly, in 96 well plate, 10 µl of standard or sample extract and 20 µl of myoglobin were added followed by 150 µl of ABTS. After incubating the plate for five minutes at room temperature, 100 µl of stop solution was added to each well and absorbance measured

Washing

Dates

SeedsDe-Seeding

Flesh Drying or Roasting

Steam-mincing

Mixing in different ratios (3, 6 and 9%)

GrindingChopping

Pressing & packing

Enriched DatePaste

Figure 1 Flow diagram of date paste enrichment.

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at 405 nm. Measurements were calibrated to a standard curve of trolox acid ranged between 0.045-0.42mM. Total antioxidant activity was expressed as mM of trolox equivalents per 100 g of sample on a wet weight basis.

Descriptive sensory analysis

Descriptive sensory analysis [15] was used to assess the sensory characteristics of enriched dates paste that was stored at ambient temperature for 10 days prior to DSA. The following attributes/descriptors, color, firmness, sweetness, flavor and desirability, on a 5-point scale were selected for evaluation. Ten male panelists, all of whom have been dealing with different aspects of dates (horticulture, protection, and processing) for at least 5 years were selected to perform the evaluation. Therefore, no standard attributes were needed because all panelists had the experience to distinguish the sensory attributes of dates. The assessment was carried out under natural daylight at ambient temperature. Dates paste samples (four samples for each assessment) were presented randomly to each panelist for evaluation. Each sample was coded with a random letter and number.

Statistical analysis

Results were expressed as mean of triplicate determinations ± standard deviation on a wet weight basis. Statistical significance (t-test: two-sample equal variance, using two-tailed distribution) was determined using the Microsoft Excel Statistical Data Analysis. Differences at p> 0.05 were considered to be significant.

RESULTS AND DISCUSSIONProximate analysis

The average moisture content of dates flesh (variety, Khalas) was 13.82%, whereas the dried and roasted seed powder were

3.67 and 0.6% respectively (Table 1). The lower moisture content of roasted seed compares to dried seeds is due to the higher temperature used to roast seeds (200°C). Seed powders contain higher protein and fat compare to dates flesh that ranged between 2.94-3.37% for protein and 7.85-7.95% for fat.

Table 2 also present the proximate analysis of date paste and different formulation of Enriched Paste (EP). Moisture content of paste (15.03%) increased significantly after adding seeds powder to range between 18.94% for DP3 to 20.69% for RP3. The increase of moisture content was mainly due to high content of dietary fiber in seed powder, which has the ability to hold higher content of water from steam-mincing process. The higher content of moisture in EP will help maintaining soft firm paste for longer time during storage.

The high content of moisture in EP also leads to higher water activity, increasing from aw 0.36 in paste to aw 0.44-0.48 in EP. However, the water activity of EP still in safe zone, as most bacteria do not grow at water activity below aw 0.9, and yeasts and molds are inhibited below aw 0.7 [16]. Water activity values can be used to predict food stability and safety more accurately than moisture content value. In addition, water activity can play a significant role in determining the activity of enzymes in foods and can have a major impact to their colour, taste and aroma [17].

Protein content of EP significantly increased (1.31-1.45%) compare to paste (1.27%). This is expected due to the higher content of protein in seeds, which was 2.94% in dried seeds and 3.37% in roasted seeds. The fat content of EP had the same pattern as protein content in seed, ranged between 0.46% for RP3 to 0.86% for RP9. This is due to high content of fat in seeds (7.85-7.95%) compares to date flesh (0.58%). This results supported by Al-Farsi et al, [3] reporting high amounts of protein and fat in date seeds compared to date flesh. Hamada et al. [6] and Besbes et al. [4] reported higher content of protein and fat in different

Moisture%

Protein%

Fat%

Ash%

Fiber%

Phenolicsmg/100g

AntioxidantsmM/100g

Dates flesh 13.82 ±0.19 a 1.56 ±0.19 a 0.58 ±0.04 a 1.85 ±0.11 a 5.11 ±0.16 a 252 ±2.9 a 873 ±52 a

Dried seed powder 3.67 ±0.16 b 2.94 ±0.16 b 7.85 ±0.20 b 1.57 ±0.19 b 61.9 ±4.1 b 3351 ±51 b 1970 ±25 b

Roasted seed powder 0.60 ±0.01 c 3.37 ±0.19 c 7.95 ±0.28 b 1.24 ±0.11 c 69.7 ±1.7 c 3386 ±54 b 2035 ±31 b

Table 1: Chemical composition of dates and seeds powder.

Values are mean ±SD of three determinations on wet weight basis. Means ±SD followed by the same letter, within a column, are not significantly different (p < 0.05).

Moisture% aw

Protein%

Fat%

Ash%

Fiber%

Phenolicsmg/100g

AntioxidantsmM/100g

Paste 15.03 ±0.48a 0.36 ±0.01a 1.27 ±0.16a 0.46 ±0.03a 1.83 ±0.05a 4.06 ±0.01a 255 ±3.9a 1108 ±17a

DP3 18.94 ±0.32b 0.44 ±0.01b 1.38 ±0.03b 0.47 ±0.01a 1.85 ±0.08a 5.57 ±0.09b 271 ±2.2b 1405 ±75b

DP6 19.82 ±0.22b 0.47 ±0.01c 1.45 ±0.01c 0.51 ±0.08b 1.92 ±0.15a 6.54 ±0.16c 285 ±18c 1628 ±27c

DP9 18.89 ±0.38b 0.46 ±0.01c 1.36 ±0.05b 0.67 ±0.02c 2.06 ±0.04b 7.65 ±0.82d 294 ±7.9c 1725 ±95d

RP3 20.69 ±0.21b 0.47 ±0.01c 1.31 ±0.05a 0.46 ±0.01a 1.94 ±0.07a 5.34 ±0.06b 285 ±1.6c 1305 ±65e

RP6 20.09 ±0.14b 0.47 ±0.01c 1.31 ±0.11a 0.69 ±0.04c 1.92 ±0.02a 7.24 ±0.17e 308 ±8.7d 1568±32c

RP9 20.14 ±0.43b 0.48 ±0.01c 1.36 ±0.05b 0.86 ±0.08d 1.96 ±0.02a 8.36 ±0.39f 318 ±8.8d 1730 ±70d

Table 2: Composition of different formulations of enriched date paste.

DP3, DP6 and DP9: Dates past with 3, 6 and 9% dried seed powder. RP3, RP6 and RP9: Dates past with 3, 6 and 9% roasted seed powder. Values are mean ±SD of three determinations on wet weight basis. Means ±SD followed by the same letter, within a column, are not significantly different (p < 0.05).

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varieties of date seeds ranged between 4.7-6.0% and 9.2-11.6%, respectively. Date seed protein is reported to contain the majority of essential amino acids; glutamic acid was the major amino acid in Deglet Nour and Allige date seeds, representing 17.8% and 16.8%, respectively [18]. Al-Hooti and colleagues [19] reported the fatty acid profile of five varieties of date seed; oleic acid was the predominant fatty acid (56.1%), followed by palmitic acid (11.9%), linoleic acid (11.6%), lauric acid (8.3%), myristic acid (6.0%), and stearic acid (2.6%). The quality of date seeds could be realized from its significant amount of mono saturated fatty acids [20].

Dietary fiber

Neutral dietary fiber contents of Khalas dates were 5.11% in flesh, 61.9% in dried seed powder and 69.7% in roasted seed powder. The high content of dietary fiber in seeds reported by Hamada et al [6] and Al-Farsi et al. [3]. Hamada et al. [6] reported 64.5 to 68.8% for total dietary fiber of three date seed varieties. Al-Farsi et al. [3] reported a higher content of total dietary fiber in three seed varieties ranging between 77.8 and 80.2%. These differences could be related to stage of maturation and varieties differences. The rich content of dietary fiber in seeds leads to increase its contents in EP to range between 5.34% in RP3 to 8.36% in RP9. The increase of dietary fiber in EP was proportional to the amount of seed powder added to enriched date paste. Dietary fiber has an important effect on EP because it holds water. Some of this water retained outside fiber matrix to create free water. This hydration provides desirable texture properties to EP. Insoluble dietary fiber (hemicellulose, cellulose, and lignin) is considered to be the major constituent of seed fiber [8]. The high nutritional value of date seeds is based on their dietary fiber content, which makes them suitable for the preparation of fiber-based foods and dietary supplements.

Phenolic contents

Table 1 shows that date seed powders are a rich source of phenolics (3351-3386 mg/100g) compares to date flesh (252 mg/100g). Comparable results are reported by Al-Farsi et al. [3] for three date seed varieties which ranged from 3102 to4430 mg /100 g. Al-Farsi and Lee [8] reported the phenolic acids of date seeds; of the nine phenolic acids detected, p-hydroxybenzoic, protocatechuic, and m-coumaric acids were found to be among the highest. Phenolics are act as antioxidants because of their ability to donate hydrogen or electron which prevent food ingredients from oxidation. The phenolics of paste in table 2 (255mg/100g) increased significantly after enriching paste with date seed powder. The increase was proportional to seeds addition, which ranged between 271mg/100g for DP3 and 318 mg/100g for RP9.

Antioxidants activity

The antioxidants activity in date flesh (873 mM/100g) is lower than dried seed and roasted seed powders which were 1970 and 2035 mM/100g, respectively (table 1). Similar results reported by Al Farsi et al [3] in three dates seed varieties; they found seeds had the highest antioxidants compare to flesh. Our results in table 2 shows phenolics and antioxidants of roasted seeds were slightly higher than dried seeds. Jeong et al. [21] reported that the total phenolics and antioxidant activity of sesame seeds after roasting

at 200°C were increased. Chandrasekara and Shahidi [22] also reported increasing of phenolics and antioxidant activity after roasting Cashew nuts at 130°C. This could be due to converting insoluble phenolics to soluble forms during heat treatment. The antioxidants of EP significantly improved from 1108 mM/100g in paste to 1305 mM/100g in RP3 and 1730 mM/100g in RP9. This result suggest that enriched date paste serve as a good source of natural antioxidants and could potentially be considered as a functional food or functional food ingredient.

DESCRIPTIVE SENSORY ANALYSIS (DSA)Figure 2 present the results of DSA for EP with dried seed

powder. Evaluation of color, firmness, sweetness, flavor and desirability of paste and enriched pastes were considered. Color is important sensory quality attribute of date paste because it’s the first property consumers observes, and losses of color are a primary concern to consumers. Addition of seeds to date paste caused a darker paste which disliked by panelist. This dislike was proportional to the % of seeds powder used giving DP9 the lowest score. Firmness of DP6 was preferred than other attributes, whereas paste was the lowest score. This was due to the higher content of moisture in DP6 compare to paste. Sweetness of paste accepted more and gradually decreased with increasing of seeds % in paste. Flavor also had a same pattern as sweetness; the increase of seeds amount used reduces the sweetness and flavor of paste. The general desirability of the paste with the highest score followed by DP3 >DP6 > DP9. Based on these results we can conclude that increasing amount of seeds to paste gradually reduce the acceptance of color, sweetness and flavor, whereas their firmness was preferred.

Figure 3 present the results of DSA for EP with roasted seed powder. Color score of EP increased in darkness with increase addition of seeds, which gave RP9 the lowest score. The degree of darkness in roasted seed is much higher than dried seed due to the roasting process which leads to Maillard browning reaction to end with darker seeds powder. Firmness was similar to dried seed powder; RP9 had the highest score and firmness gradually decreased with decreasing of seed % to reach lowest in paste. Sweetness and flavor of paste preferred much than enriched

0

1

2

3

4

5Color

Firmnes

Sweetness Flavour

DesirabilityP

DP3

DP6

DP9

Figure 2 Sensory analysis of date paste enriched with dried seed powder (P is dates paste without seed powder, DP3, DP6 and DP9 are dates paste with 3, 6 and 9% dried seed powder respectively).

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date paste, as these attributes reduced with increasing of seeds. Therefore, the desirability was for paste followed by RP3, RP6 and RP9.

Figure 4 shows the comparison between two samples of DP3 and RP3. These formulations were the most preferred pastes among enriched date paste. Color score of DP3 was better than that of RP3, whereas firmness of the both samples was better than paste. Sweetness and flavor remained more preferred in paste followed by DP3 and RP3. Therefore the general desirability was for the paste followed by DP3 and RP3. From DSA results, DP3 could be the most accepted enriched date paste to the panelist.

The added value of EP

Figure 5 shows the percentage of increase in contents of moisture, weight, fiber and antioxidants in enriched date paste DP3. The addition of 3% of dried seed powder to date paste added functional and economical value. Moisture content of DP3 was increased by 26% which leads to softness of the paste. This improved the sensory preference of the paste and reduced the hardness during storage. The addition of seeds increases the paste weight by 29% which will lead to increase the profit from producing such products. The dietary fiber and antioxidants of DP3 were increased by 37% and 27%, respectively. This has a huge impact to the functional value of date paste and to the marketing of this product.

CONCLUSIONUtilization of date seeds, a by-product of the date processing,

into a new value added product was attempted. We enriched date paste with seed powder in 3, 6, and 9% to formulate different products of date paste and evaluated for their proximate composition, dietary fiber, phenolics, antioxidant activity and sensory quality. We found that enriched date paste with 3% dry seed powder (DP3) was the best formulation that showed improved firmness, dietary fiber, antioxidant activity and sensory quality of the product.

ACKNOWLEDGMENTSThe authors would like to thank Al Foah Company, Al Ain,

00.5

11.5

22.5

33.5

44.5

Color

Firmnes

Sweetness Flavour

DesirabilityP

RP3

RP6

RP9

Figure 3 Sensory analysis of date paste enriched with roasted seed powder (P is dates paste without seed powder, RP3, RP6 and RP9 are dates paste with 3, 6 and 9% roasted seed powder respectively).

0

1

2

3

4

5Color

Firmnes

Sweetness Flavour

Desirability

P

DP3

RP3

Figure 4 Sensory analysis of date paste of DP3 & RP3. (P is dates paste without seed powder, DP3 is dates paste with 3 dried seed powder, RP3 is dates paste with 3% roasted seed powder).

0

5

10

15

20

25

30

35

40

Moisture Weight Fiber Antioxidants

26 %29 %

37 %

27 %%

of I

ncre

ase

Figure 5 The percentage of increase in enriched date paste DP3.

for providing the date samples. We would like to extend our gratitude to Mr Ramadan El-Sayed and Mr Mahmood Abdul-Aziz from Al-Salamat Research Station, ADFCA for their assistance in dates analysis.

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Al-Farisi MA, Lee CY (2014) Enrichment of Date Paste. J Hum Nutr Food Sci 2(3): 1032.

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