Handbook of Vanilla Science and Technology

Italian researchers (Bettazzi et al. 2006) developed an interesting disposable electrochemical sensor, which can be used for the determination of vanillin in natural extract concentrates and in the finished products yogurt and compote. This vanillin method was comparable to HPLC. The electrochemical behavior of other compounds: vanillic acid, p-hydroxybenzaldehyde, and p-hydroxybenzoic acid was also investigated.

As noted earlier, the extraction of vanilla using organic solvents can affect the measurement of the chemistry and indeed the efficiency too. Mexican researchers (Valdez-Flores and Canizares-Macias 2007) developed a method for efficient vanillin extraction with ultrasound assisted extraction (USAE). This extraction with the continuous flow dilution was shown to be more efficient and quicker than the more common soxhlet and maceration extraction. Mexican researchers (Longares-Patron and Canizares-Ma-cias 2006) developed a microwave based extraction process for vanillin and p-hydro-xybenzaldehyde and obtained the ratios with UV analyses at 348 and 329 nm, respectively, with Vierordt’s method. A statistical optimization of the extraction conditions was investigated, which permitted the claim of faster extraction and increased vanillin and p-hydroxybenzaldehyde concentrations.

Sinha et al. (2008) published an interesting review of vanilla, which included an extensive review of biological activity of this product. Antimicrobial, antioxidant, and a variety of disease resistant, amelioration effects were described, as well as insect repellent activity. Extraction methods were described, both conventional percolation and soaking as well as non-conventional methods including SCO₂. A variety of analytical techniques used to investigate vanilla were also discussed, including TLC, HPLC, GC, and electrophoresis. They also discussed the production of vanillin and the methods to detect the adulteration of this unique product.

An interesting use of capillary electromigration-microchips was investigated by Avila et al. (2007). They applied this electrochemical detection technique to five flavor constituents: vanillyl alcohol, ethyl maltol, maltol, ethyl vanillin, and vanillin. When analyzing actual samples they focused on vanillin and ethyl vanillin, as the latter would immediately reveal adulteration, but all constituents were analyzed.

While the application of either a GC or HPLC procedure in order to determine vanilla quality is a desirable goal, Hoffman et al. (2005) have shown a more comprehensive analytical approach using both techniques may lead to a procedure more applicable to determining the quality of vanilla extract and its correlation to sensory measurements. In this approach, the authors used a combination of GC analysis, using the SPME sampling technique and a stir bar sorptive extraction (SBSE) sampling for reversed phase HPLC analysis. Gas chromatography analysis separated greater than 100 constituents. Ten of the volatiles, which occur in most vanilla extracts, were targeted. Fifty-five multifold vanilla extracts of beans from Madagascar, Indonesia, Comores, Mexico, Tonga, Uganda, and Tahiti, as well as extracts of blended origins, were analyzed by GC for volatile constituents and by HPLC for the four noted vanilla-phenolic compounds. These 55 extracts were also extensively evaluated by a sensory group of highly trained descriptive panelists, defining the vanilla’s flavor and aroma characteristics. Table 10.3 summarizes the statistical influence of several key compounds in relation to the sensory parameters described by the panelists. A total quality vanilla (TQV) assessment factor established a means to quantify the sum of the quality attributes in vanilla. Factor analysis was used to evaluate the analytical chemical data from 14 chemical constituents (10 by GC and 4 by HPLC) in each of the 55 vanilla samples.

Table 10.3 Statistical factor analysis of combined GC and HPLC data for sensory analysis. Bolded compounds contribute positively to the statistical factor

Factor Structure (correlations)

― | Factor 1 Age-related Compounds | Factor 2 Rummy Resinous | Factor 3 Vanillin Flavor | Factor 4 Smokey Phenolic

Total Variability

explained = 86% | ― | 45% | 19% | 12% | 10%

4-Hydroxybenzoic acid | ― | —0.01226 | —0.05422 | 0.16541 | 0.75172

Vanillic acid | ― | 0.28421 | 0.26838 | 0.60821 | 0.70989

4-Hydroxybenzaldehyde | ― | 0.56672 | 0.42593 | 0.93793 | 0.28968

Vanillin | ― | 0.50772 | 0.39799 | 0.92226 | 0.25951

Ethyl acetate | ― | 0.97844 | 0.34279 | 0.56633 | 0.06165

Acetaldehyde diethyl acetal | ― | 0.32885 | 0.73236 | 0.59983 | —0.12226