USING ANALYTICAL METHODOLOGIES TO ASSESS THE ORGANOLEPTIC CHARACTER OF CITRUS ESSENTIAL OIL

Abstract

Essential oils are natural products used to flavor food and beverages. With the increase in nutrition conscious consumers, manufacturers of food additives and food products are faced with the challenge of making healthy alternatives. In particular, food products going to market with label claims stating reductions in sugar and salt, organic certified, organic compliant, and all natural; moreover the ingredients used in flavors must meet these label claims as well. More often than not, the challenge in using ingredients that follow these requirements is the pricing, the sourcing and the variability among those sources. Variability is common in the ingredients coming from nature such as fruits and plants because the area of cultivation can vary by the soil at the sight of planting and/or the climate in the region. Pricing is also problematic in naturally grown ingredients because it is a matter of supply and demand. Stock could be depleted from natural disasters, disease carrying pest(s), pests that consume the crop, and/or other causes for scarce supply of crop(s). Essential oils are natural byproducts of fruit, peels, and leaves from plants that contribute to flavor formulae for a large variety of food products. Because the essential oils are a crop based commodity, every variety has inherent differences based on the growing conditions and their ripening stages [1]. Nevertheless, each type of oil has marker chemicals that make up the majority of its composition; these marker chemicals have the tendency to degrade over time based on their interaction with light, oxygen exposure, and temperature. For companies that manufacture flavorings, understanding the variability among sources of essential oils as well as the possible degradants of essential oils is valuable information to obtain because it is possible the variants and degradants will negatively impact the flavor profile. Flavor is without question the most important attribute of the food we consume and by default stability of said flavor(s) need to be understood [30]. The content in this dissertation involves the stability analysis of a common essential oil, Oil Mandarin Italian Select, from Citrus Reticulata Blanco. It has known off notes that form from unknown causes. Most common is the plastic note that has formed in carbonated products like soda. Studying this particular essential oil in various conditions is intended to shed light on what those degradants are and under which conditions they form to give mandarin oil an off-note when applied to high acid and carbonated beverage applications. Once the note is reproduced, a correlation between analytical data and sensory interpretation of the oil will be developed. Mandarin essential oil being in the Citrus genus is traditionally analyzed via gas chromatography (GC) because of the high quantities of volatile constituents that give an oil high aroma activity. The volatile fraction of mandarin oil to be studied includes stability of methyl-N-methylanthranilate (MNMA), a major component giving mandarin its distinct grapey character, as well as gamma terpinene, thymol, sinensal, alpha pinene, beta pinene, myrcene, para cymene, alpha terpineol, and beta caryophyllene. Each of these ten compounds contributes to the unique flavor profile of mandarin oils when compared to orange and tangerine essential oils [1]. It was the common knowledge that para cymene can be perceived as rancid in aroma and the many interconversions the terpenes make that cause para cymene formation in Citrus oils, which made monitoring the changes of this chemical in the three stability environments crucial. Attention is being paid to para-cymene, as a specific marker of degradation in Citrus. The data obtained from the applied stability studies were challenging to understand as the marker chemicals are volatile and sensitive to chemical change. In this work the chemical changes and trends were analyzed under various storage conditions. Significant statistical analyses were employed to help define criteria of usability. The analyses were required because of natural variants and apparent inconsistencies of the data. Dixon Q Test and the Z Test were applied to determine outliers. Additionally, the Bland Altman method was applied to compare storage conditions and to determine if this statistical approach could be used to define significant changes in the marker chemical stability. The Bland Altman plots suggest that each component met the statistical limits of agreement, meaning the samplings were not significantly changing, statistically speaking. A final approach to assess the analytical data of the mandarin oil for significant change was the mass balance of each marker chemical from week 0 to week 24. Instrumental fluctuations have an acceptable range of +/- 20% in the industry; hence, a significant change criterion for a chemical in the mass balance must be one that exceeded +/- 20%. Unlike classical statistic methods, the mass balance was indicative that significant change had occurred to the compounds in the three studies. Upon sensory analysis of the oil samples, display of plastic note, oxidation, and overall loss of characteristic mandarin notes, the mass balance was found to correlate best to the significant change detected by sensory evaluation of the oil samplings. Due to the inadequate number of validated methods on Citrus essential oil research and the absence of large groupings of terpenes validated in a unified methodology, reconciliation of mass balance is an underutilized method of assessment in the literature. As a final assessment of the GC method validated, a product containing the selected mandarin oil was analyzed to evaluate the ability of the method to separate the oil components within a significantly more complicated matrix than the initial samples. The method was successful though not all marker chemicals were detected due to their low formulation concentration being below the level of detection of the method. This should not be seen as a failure of the method. For the major components of the essential oil studied, the method was quantitatively successful, meeting industry requirements.