Physicochemical Properties and Quality Evaluation of Porphyra acanthophora in the Philippines

Abstract

Seaweeds and its hydrocolloids have captured the attention of various researchers in exploring its biologically active substances, mostly to develop foods and drugs beneficial to human health. Generally, major component of seaweeds are carbohydrates, proteins and the least are lipids which varies from species to species and environmental conditions. Physicochemical properties and quality of Porphyra acanthphora were described in each chapter. Chapter 1 deals with the proximate composition, mineral content, total amino acids and some physicochemical properties, Chapter 2 deals with the antioxidant potential and Chapter 3 deals with the volatile compounds and compared in the different products of Pophyra by using headspace gas chromatography and mass spectrometry (GC-MS). Proximate analysis revealed that Porphyra acanthophora contained 47.4±0.7 % of carbohydrate, 23.0±0.1% protein, 1.1%±0.1 crude lipid, 16.7%±0.1 ash and 11.8%±1.5 moisture. ICP emission spectrometry showed that macrominerals such as K, Na, Mg, P and Ca were present in the sample with corresponding amount, 29,291.0, 23,040.3, 5,350.0, 3,018.1, 2,218.7 in mg/kg respectively. Total amino acids determination showed that Porphyra acanthophora contained 24 amino acids. Seven among the 24 identified are essential amino acids, which are threonine (30.6m/100g), valine (10.9 mg/100g), lysine (9.3 mg/100g), tryptophan (6.0 mg/100g), leucine (4.7 mg/100g), isoleucine (4.4 mg/100g) and phenylalanine (3.1 mg/100g). Meanwhile, physicochemical properties like water retention capacity and lipid adsorption capacity of Porphyra acanthophora were determined. Water retention capacity was 5.6g/water.g-1 dry sample and lipid adsorption capacity of 3.3±0.2, 3.3±0.2, 2.9± 0.1 g/oil.g-1 using soybean, sesame and sunflower oil respectively. Five kinds of solvents such as distilled water, 70% aqueous acetone, ethanol, petroleum ether and chloroform were used to explore the antioxidant potential of Porphyra acanthophora. It was explored by screening phytochemicals, analyzing the phenol content and measuring the antioxidant activity such as DPPH radical-scavenging and Fe-chelating activity. Extraction of bioactive compounds from seaweeds depends on solvents used. DPPH radical-scavenging activities of the different extracts revealed significant differences as compared to control and scavenging activities ranged from 12.33% to 39.13%. Meanwhile, distilled water extract Fe-chelating activity was significantly different from the other four extracts while ethanol and ether, and chloroform and aqueous acetone were not significantly different. Fe chelating activities of the different extracts ranged from 60.3 % to 92.9 %. Total phenolic content (TPC) exhibited significant differences among extracts and TPC ranged from 15.0 to 38.5mg/GAE/g dry sample. Phytochemical screening showed that saponins, glycosides, triterpenes, phytosterols, alkaloids, protein and amino acids, diterpenes, phenols and tannins were present, while flavonoid was absent. With these findings, Porphyra acanthophora is a good source of natural antioxidants that is comparatively similar to terrestrial plant sources of natural antioxidants. Volatile compounds of dried Porphyra acanthophora was determined using headspace Gas Chromatography-Mass Spectrometry (GC-MS). Compounds identified have taken into consideration the importance for flavor rather than their volatility. It was further compared among processed products Porphyra in Korea without oil and using different vegetable oil such as grapeseed, olive, sesame, and perilla. A total of 192 volatile compounds were identified and classified into aldehydes (16); alcohols (31); ketones (17); esters (19); ethers (3); nitrogen-containing substances (3); sulfur-containing substances (5); furans (7); other aromatic compounds(8); and other aliphatic hydrocarbons(83).