Middle East Journal of Applied Volume : 07 | Issue :03 |July-Sept.| 2017 Sciences Pages: 613-625 ISSN 2077-4613 Functional characterization of luffa (Luffa cylindrica) seeds powder and their utilization to improve stabilized emulsions Rabab H. Salem Food Science and Technology Department, Faculty of Home Economics, Al- Azhar University, Tanta, Egypt. Received: 10 July 2017 / Accepted: 20 August 2017 / Publication date: 28 Sept. 2017 ABSTRACT There is an increased necessity to discover new sources of proteins used as functional ingredients in different food systems. The aim of this research is using luffa (Luffa cylindrica) seeds for producing functional powder can be used as emulsifier agent with studying its nutritional properties. The results showed that, the content of crude protein obtained was 28.45%. The high total carbohydrate (60.95%) for Luffa seeds powder. The most concentrated amino acid in the seeds powder was glutamic acid (11.56 g/100g); while aspartic (10.98g/100g) was the most concentrated non-essential amino acids. On the other hand, the highest scoring essential amino acid was tyrosine (2.60); while threonine was the lowest scoring amino acid (0.97) making it the first limiting amino acid. The results also showed that, the bulk density was 0.40 g/cm3 for seeds powder. The water absorption capacity of luffa seeds powder was 235% while oil absorption capacity was 85% and the least gelation concentration was 12% which reveal its functional properties, thus it can be used for binding water and oil in food systems. The cytotoxic results showed that CC50 value of Luffa seeds powder on BHK cell line was >200 µg/ml. The emulsifying properties of O/W emulsion (ESS, ESC and TSE) were enhanced with the increasing level of luffa seeds powder but still lower than that of control (sodium casinate). Key words: plant proteins, amino acids profile, phytochemical composition, emulsifying agent, cytotoxic activity. Introduction The problem of protein malnutrition in the developing countries is of great importance, as a large number of people in this part of the world do not have access to cheap protein sources (Adebowale and Lawal, 2003). Seeking sources of plant proteins has attracted increasing interest due to consumers’ growing concerns over the safety of animal-derived products. Recently, with rising public concern about increasing protein consumption and shortage, has stimulated research on developing new sources of protein from unexploited sources or wastes (Perumal et al., 2001). There is an increased necessity to discover new sources of proteins to be used as functional ingredients in different food systems. Plant proteins have been used extensively for many years in the food industry as food product ingredient due to amino acid content (Horax et al., 2004). Luffa (Luffa cylindrica) is a member of cucurbitaceouse family. One mature Luffa sponge will produce at least 30 seeds (Oboh and Aluyor, 2009). The seeds have laxative properties due to their high oil content. It contains a wide range of secondary metabolites with distinct biological activities. The seeds have been reported to be useful in the treatment of asthma, sinusitis and fever (Nagao et al., 1991). It is reported to possess antiviral, anti-tumor, antioxidant, anti-inflammatory and immunomodulatory activities (Tannin-Spitz et al., 2007). L .cylindrica seed contains a high proportion of essential amino acids and has a low atherogenic potential. Flavonoids (4.53%) were the most concentrated phytochemical in the seed flour while saponins, alkaloids and cardiac glycosides were also present (Lucy and Abidemi, 2012). Seeds are rich sources of minerals but the bioavailability of these minerals is usually low due to the presence of antinutrients (Valencia et al., 1999). These antinutrients interfere with absorption of nutrients from foodstuff thus affecting their metabolism. Soaking seeds/grains in alkali solutions (Reichert et al., 1980) have been reported to overcome the harmful effects in seeds. Treatment with sodium Corresponding Author: Rabab H. Salem, Food Science and Technology Department, Faculty of Home Economics, Al- Azhar University, Tanta, Egypt. E-mail: [email protected] 613 Middle East J. Appl. Sci., 7(3): 613-625, 2017 ISSN 2077-4613 bicarbonate solution is more economical and easier to handle than acid treatments (Mahmood et al., 2007). There are two basic forms of emulsion. The first is the oil-in-water (O/W) emulsion, in which oil droplets are dispersed and encapsulated within the water column, while the second is the water-in- oil (W/O) emulsion, in which droplets of water are dispersed and encapsulated within the oil (Gonglun and Tao, 2004). Protein and oil are two key ingredients in food emulsions (Melik and Fogler, 1998). Functional and physico-chemical properties of proteins such as texture, solubility, water absorption capacity, oil absorption capacity, foaming capacity, gel formation, etc. are indices that may be used in food formulations (Hermansson, 1979 ; Adeyeye and Aye1, 1998 and Soares de Castro et al., 2015) .The first objective of this study was to produce powder from Luffa seeds and characterize their nutritional and functional properties. The second objective was to develop model emulsion using Luffa seeds powder and characterize their emulsion properties. Materials and Methods Materials: Luffa seeds: Loofah gourds were harvested during the month of November. The gourds were shaken to remove the seeds manually. The seeds of (Luffa cylindrica) were collected from private farm at Abo- keeper City, El-Sharkia Governorate, Egypt. Other Ingredients: Corn oil was purchased from local market at Shubra-El-Kheima, Qaliubiya Governorate, Egypt. Sodium caseinate (90.34% protein, 5.83% water, 1.9 fat and 5.43% ash) and sodium benzoate were purchased from Chemicals Company El Rahma , Egypt . Methods: Preparation of luffa seeds powder: The immature seeds and extraneous materials were removed. The remaining seeds were washed. They were soaked in 0.1% sodium bicarbonate for 12 hr. A seed to water ratio of 1:5 (w/v) was used. The soaked seeds were rinsed twice in distilled water and oven dried at 50 °C. The dried seeds were dehaulled manually. The sample was defatted by soaking in petroleum ether for 24 hours with shaking. The ratio of solvent to crushed seeds was 3:1(v/w). The soaking was repeated three times. luffa seeds powder packed in polyethylene bags and stored at 4°C until utilized. Preparation of oil-in-water emulsions: Oil-in-water emulsions (v/v) were prepared by the slow mixing of 10 ml corn oil (added gradually) with 90 ml of emulsifier solutions which prepared by dispersed of 1% (E1sample), 2% (E2sample), 3% w/v (E3sample) luffa seeds powder and sodium caseinate 1% w/v (control) into deionized water, followed by stirring for 2 h at ambient temperature, stored overnight at 4°C to ensure complete dissolution, then solutions were homogenized for 2 min at 3000 rpm .Sodium benzoate was added at a concentration of 0.1 w/v in the continuous phase as an antimicrobial agent. Analytical Methods: Proximate composition: Moisture, ash, protein, fat and fiber content were determined according to AOAC (2005). Moisture was determined by drying sample at 105°C to constant weight. Ashing was performed at 550 °C for 6 hrs in a muffle furnace. Protein was analyzed using kjeldahl method; factor of 6.25 was 614 Middle East J. Appl. Sci., 7(3): 613-625, 2017 ISSN 2077-4613 used for conversion of nitrogen to crude protein. Fat was calculated by weight loss after extraction with petroleum ether in sohxlet apparatus. Crude fiber was determined. Carbohydrate contents were estimated by differences. The energy values obtained for carbohydrates (x17kJ), crude protein (x17 kJ) and crude fat (x37 kJ) for the sample. Minerals analysis: Minerals were determined by the method described by AOAC (2005) at the High Institute of Public Health, Alexandria. Sodium, potassium and calcium were determined using Flame photometer apparatus. Magnesium, iron, zinc and manganese were determined using Atomic Absorption Spectrophotometer. Amino Acids Analysis: The amino acids profile was determined using methods described by (Cohen et al., 1985) using Amino Acid Analyzer (Beckman, model No119 CL) at the Faculty of Agriculture, Mansoura University, Egypt. The sample was hydrolyzed with 6N hydrochloric acid (10 ml) with 0.1% mercaptoethanol in a sealed tube at 110 °C for 24 hours. After cooling at room temperature, the hydrolyzed samples were filtered through Whatman No. 1 filter paper and the filtrate was diluted with distilled water to 25 ml in a volumetric flask. 5 ml of the diluted filtrate was dried in a vacuum desiccator in the presence of potassium hydroxide. The result dried residue was dissolved in 1 ml of sodium citrate buffer (pH 2.2) and stored at 4°C until analysis. Functional properties: Bulk density: Bulk density determination carried out using the procedure of Mepba et al. (2007). A specified quantity of the sample was transferred into a weighed measuring cylinder (W1). The cylinder containing the sample was weighed (W2). The bulk density was determined from the relation: Bulk density (%) = W2 −W1 /Volume of sample Water absorption properties: Water absorption capacity was determined using the method of Sathe and Salunkhe, (1981) as modified by Adebowale et al. (2005). Ten milliliter of deionized water was added to 1.0 g of the sample in a beaker. Followed by centrifuging at 3500 rpm for 30 min and the supernatant measured in a 10 mL graduated cylinder. The water absorption capacity has been expressed as a percentage: Weight of absorbed water x100 Water absorption capacity (%) = Sample weight Oil absorption properties: The oil absorption capacity of sample was determined by the method of Ghavidel and Prakash (2007). A sample was mixed with 5 mL of corn oil in a centrifuge tube for 1 min, held for 30 min at room temperature, and centrifuged for 25 min at 5000 rpm.