Journal of Food Processing & Technology

Protein Utilization, Immune Function, and Hepatic Antioxidant Activity of Rats Fed Tahini in Combination with Other Oily Seeds

Ghiath Sumainah¹ and Louay Laban^{2* 1}Department of Biological Science, Syrian Private University, Damascus, Syria
²Department of Nutrition, Al Rashed Private University, Damascus, Syria
^*Correspondence: Louay Laban, Department of Nutrition, Al Rashed Private University, Damascus, Syria, Email:

Received: 22-Mar-2021 Published: 04-May-2021, DOI: 10.35248/2157-7110.21.12.895

Introduction

In various parts of the world efforts are being made to increase the consumption of vegetable protein from locally available sources. Sesame paste (Tahini) has a reputation as a popular food in East- Asia and in Middle-East countries [1]. It is made from ground, dehulled, dry-roasted sesame seed (Sesamun indicum L). The high oil content of approximately 60% consists mostly of oleic (39%) and linoleic (40%) acids [2]. Sesame paste also contains relatively high protein content (26%) and a low percentage of crude fiber and moisture [3].

The oil in sesame is remarkably stable and resistant to oxidative deterioration due to indigenous fat and non-fat antioxidants (tocopherols and lignans) [4-6]. Many of these antioxidants exist as the glucosides of sesamol, sesamin, sesaminol, sesamolinol, and pinoresinol [7]. There is evidence that the glucosides act as potent in vivo antioxidant substances [4,8]. In addition, they are capable of altering prostaglandin synthesis, thereby potentially affecting immune function [9]. Thus, increasing the rationary intake of sesame may improve health status. However, sesame use, especially for the preschool child, is hampered by the poor quality of its protein. Sesame is very low in lysine. Yet, the protein is exceptionally rich in sulfur-containing amino acids, whereas these building blocks are present at low levels in most other seed proteins [3]. Complementing sesame protein with other sources of seed protein has been shown to enhance overall protein quality [10,11]. Chickpea, peanut, and soybean are good complementary foods due to their widespread availability in the Middle-East and Asian countries.

The purpose of our study was to evaluate sesame seeds in combination with chickpea, peanut, and soybean, as a means to significantly raise the protein quality and to possibly demonstrate its antioxidant and immune stimulating properties in the rat.

Materials and Methods

Processing of seeds: Sesame paste (Tahini), the standard commercial made from Sesamum indicum Linn, was purchased through a supplier in 20 kg plastic buckets from Lebanon (Al-Kanater Factory, Beirut). It was kept under refrigeration until used. A protein of the paste was partially defatted by repeated centrifugation (4000 g) until no further oil would separate.

Raw chickpea (Cicero arietinurn Linn) was supplied from a commercial source, raw soybean seeds and heat-treated peanuts were obtained from the Department of Agronomy at the University of Damascus. The chickpea and soybean seeds were soaked with water (3:1) for 18 hours and then drained. Soaked soy was boiled in 0.5% Nabicarbonate for 45 minutes to inactivate the antinutritional factors.

Chickpea was autoclaved at 121°C for 45 min. Excess water was eliminated and the seeds were air-dried, freeze-dried, and then ground to pass 1 mm mesh. The proximate analysis is presented in table 1

Table 1: Proximate Analysis of the Protein Sources.

Ration treatments (Table 2): All rations were formulated in the laboratory prior to the launch of the study and they were mixed in a Hobart mixer and fed in powdered from. There were two control rations, namely CON, made with casein with soy oil, and CS, containing casein and sesame oil. The groups were sesame pastechickpea (SC) (protein source 25%, 75% respectively). Sesame paste alone (S) (protein source 100%), and sesame paste-peanut-soy (SSP) (protein source 50%, 25%). All rations were formulated to give 10% total fat and 10% crude protein.

Table 2: Compositions of the rations.

PER

60 Syrian or golden Hamster Males (Mesocricetus auratus) (weighing 41 g ± 1 g) were purchased from the local laboratory animal breeding establishment (Damascus, Syria). These animals were acclimated to the laboratory for 3 days before initiating the experiment. All procedures for laboratory animals were in accordance with approval of the Institutional Animal Welfare Committee of the Syrian Private University. The Syrian hamsters were housed individually in stainless steel cages with 12-Hr light/dark cycle. They were randomly assigned into five groups (n=12), and given water and food ad libitum. Their body weights and food intakes were recorded weekly for four weeks. Spilled food was collected and accounted for in tabulating weekly food intake.

PERs were calculated according to AOAC [12]. All values were then standardized to the CON group set to 2.50.

Cell-mediated immune function assay

At the end of the PER assay 7 animals from each group were subjected to an in vivo Delayed-Type Hypersensitivity Reaction (DTH) assay procedure as follows [13-15]. On day 1, the rats were anesthetized with Ketamine (80 mg/kg body weight), shaved over the abdomen, and painted with 100 μ of 1% DNFB (Dinitroflourobenzene) in 4:1 acetone: olive oil. On the second day, another application of DNFB on the abdomen was made without anesthesia. On day 4, one ear was challenged with 50 μ of 0.5% DNFB in the vehicle. The other ear was painted with the vehicle to serve as the non - stimulated control ear. After 24 hours, ear thickness (swelling) was measured with a precision micrometer. The level of DTH response was quantified by the difference of ear swelling between the stimulated and non-stimulated ears in the same animal, expressed as the ratio of thickness of treated over untreated ear. A greater degree of swelling of the treated ear is indicative of a stronger immune response.

Antioxidant activity: The remaining five hamsters of each group were anesthetized. The liver was harvested, weighed and frozen pending analysis. Liver tissue was also collected and analyzed from the rats were subjected to the DTH test above. Antioxidant activity was measured by the Glavind method using α, α- Dipheyl- Picrylhydrazyl (DPPH) [16,17].

All data were subject to Analysis of Variance (ANOVA) using SAS, version 6.12 (SAS Institute, Cary, North Carolina). Duncan's multiple range tests were used to detect differences among treatment means if the F-value was significant. All effects were considered significant at P<0.05.

Results and Discussion

Protein Utilization Standardized (Tables 3 and 4): Food intake and weight gain over the 4-week feeding study was highest for the Casein Soy Oil (CON) Control group. The Casein Sesame (CS) oil control group showed slightly lower food intake and weight gain but had the same PER as the CON rats.

Table 3: Efficacy of protein utilization of rations containing sesame paste or combinations of sesame paste with chickpea, soy, and peanut.

Table 4: Protein Digestibility Corrected Amino Acid Score (PDCAAS) using the pre-school child's amino acid requirements as reference.

In the group on the Sesame Chickpea (SC) ration, food intake was 3% less than the CON group but weight gain was 23% lower, the PER value of 2.18 was 13% less than the CON group Rats on the Sesame Soy Peanut (SSP) ration had significantly less food intake and weight gain than the CON group; the PER was only 1.59. Lastly, rats consuming the ration containing Sesame (S) as the only protein source showed a markedly low food intake and a weight gain of only about 4 g per week; the PER of 1.08 was significantly lower than all other rations treatments.

Calculations of the Amino Acid Score as well as the Protein Digestibility Corrected Amino Acid Score (PDCAAS) using the FAO/WHO reference values for the pre-school child are compared to evaluate the quality of a protein for humans [18]. Digestibility factors for the seed proteins are 85% for sesame, 88% for chickpea, and 95% for both peanut and soy [18]. For the ration containing sesame as the sole protein source (S), the low lysine score of 0.56 and the PDCAAS of only 48 is consistent with its low PER of 1.08. The combination supplying 25% sesame protein plus 75% chickpea protein (SC) increased the lysine score to almost unity while maintaining the ratios of all other essential amino acids at or well above 1.0. The PDCAAS rose markedly to 83, which was reflected by a doubling of the PER. Enriching sesame protein with Soybean and Peanut (SSP) improved the lysine score to 0.73 and the PDCAAS to 64, but these changes failed to raise the PER above 2. Any further dilution of the sesame protein with soybean and/or peanut would theoretically compromise the threonine ratio and thus the PDCAAS and PER. In general, a PER value below 1.5 indicates a protein of low quality, between 1.5 and 2.0 of intermediate quality, and above 2.0 as good quality [19]. Thus the SC ration would be classified as a good quality protein source.

Hepatic Antioxidant Activity: Among the major body organs, the liver is known to contain the highest concentration of antioxidant substances [15]. In our study, the two control groups showed almost identical antioxidant activity of the liver. Thus, the sesame oil added to a Casein Sesame (CS) did not enhance antioxidant activity in the liver compared to the casein ration containing soybean oil as the fat source (CON). In all three rations treatments which contained sesame paste, the liver antioxidant activity significantly. The SC group showed 33% higher activity compared with the controls, while the S and SSP groups were up by 64% and 76%, respectively. Kang et al., [20] recently reported that the addition of 10 defatted sesame flour led to a significant reduction in oxidative stress as measured by lipid peroxidation of hepatic tissue in rabbits. It is evident that even a ration containing only 25% of the total protein as sesame was of significant benefit to hepatic antioxidant capacity. Moreover, rations containing at least 50% of the protein as sesame (SSP and S) resulted in further statistically significant increases in antioxidant activity (Figure 1).

Figure 1: Liver antioxidant capacity in rats fed rations contains sesame paste or combinations of sesame paste with chickpea, soy, and peanut.

In vivo cell-mediated immunity (delayed-type hypersensitivity): In comparison to the CON group, rats on rations SC, SSP, or the control ration containing Sesame Oil (CS) all showed similar responses to the DNFB immune function assay. This indicates that rations with these plant protein combinations or a casein ration with sesame oil as the only fat source were effective at promoting a normal immune response to a challenge, and that this response was unrelated to PER values. The group on the ration containing only Sesame Paste (SP) as the protein source demonstrated significantly stronger immune function compared with all other groups. The explanation for this finding may be related to the moderate level of malnutrition by rats in this group as a consequence of their markedly low food intake and weight gain.

Figure 2: In Vivo cell-mediated immune response as measured by dnfb assay in rats fed rations containing sesame paste of combination of sesame paste with chickpea, soy, and peanut.

Whereas severe malnutrition leads to depressed immunity, moderate malnutrition or undernutrition is known to improve the cellular immune response [21,22]. The voluntary food intake of rats in the S group was approximately one-third lower than the other groups while weight gain was less than one-half of any other group. This response was most likely due to the low lysine content of sesame protein, which led to a degree of undernutrition sufficient to alter immune function. In the two other groups that consumed rations containing sesame in combination with other seed proteins (groups SC and SSP) food intake and weight gain were affected to a much lesser extent, resulting in only a very mild state of undernutrition. This was apparently insufficient to alter immune function compared with the control groups.

Conclusion

In summary, the SC formulation containing protein in a ratio of 1 part sesame to 3 parts chickpea resulted in an amino acid pattern that met 95% of the lysine needs and at least 10% of all other essential amino acids as recommended for the pre-school child. The comparatively high PER confirmed the favorable nutritive value of this protein combination. In addition, this sesame-chickpea combination enhanced liver antioxidant activity and supported a normal response to a cell-mediated immune test in comparison to an isonitrogenous casein-based ration.

Conflict of Interest

The authors declare no conflicts of interest.

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