Oxidative stability and sensory perception of alpha-linolenic acid enriched foods during storage

Abstract

Alpha-linolenic acid (ALA) is a polyunsaturated fatty acid (PUFA) essential in the human diet. ALA is a metabolic precursor of longer chain omega-3 PUFA. In most Western countries, recommended omega-3 PUFA consumption is not being met. Thus, enriching foods with omega-3 rich sources, such as linseed oil, is of interest. However, due to its polyunsaturated nature, ALA is highly sensitive to processing and is easily oxidized. Microencapsulation by spray-drying of linseed oil offers a potential solution to enrich food with ALA while hindering oxidation. Thus, this study investigated the oxidative stability and sensory perception of chocolates and cookies with microencapsulated linseed oil during storage.

The microcapsules were added to cookies and chocolates in concentrations that met health claim for omega-3 PUFAs. For the storage stability test, cookie samples were stored at 50 °C for 25 days and the chocolate samples at room temperature for 11 weeks. The sensory evaluations of fresh and stored samples were conducted at the end of the storage time using descriptive analysis method. Of the collected samples, the ALA concentration was analyzed with gas chromatography with flame ionization detector. Oxidative stability was evaluated with peroxide value (PV). Identification of volatile compounds was performed with solid phase micro-extraction gas chromatography-mass spectrometry (SPME-GC-MS).

The ALA concentration in the capsules (25 g/100 g) was not not lost in baking or chocolate preparation. A lower PV was determined in chocolate (3.25 – 1.62 meq/kg) than in cookies (5.95 – 11.63 meq/kg). The analysis of volatiles in the food samples also indicated that there was a lower concentration of oxidation volatiles in chocolate than in cookies. Furthermore, cookies and chocolates containing capsules including of pea protein and maltodextrin contained the least volatiles originating from lipid oxidation. Sensory evaluation (p > 0.05) indicated that linseed oil (as such or contained in a capsule) affected appearance and texture of the cookies and chocolates. Development of off-odors and off-flavors was detected in stored cookies and chocolates samples containing capsules made with whey protein and maltodextrin and capsules made with soy protein and maltodextrin. It was also observed, the higher the ALA concentration, the higher the oxidation degree; samples containing 0.6% ALA were rated as having the strongest rancid aroma and flavor.

Capsule material made of pea protein and maltodextrin offered the best protection against oil oxidation and the most similar sensory qualities when compared to the reference samples.