The Analytical Approach
Menard G. Heydanek, Jr. Flavor Technology John Stuart Research Laboratories The Quaker Oats Co. 617 W. Main Street Barrington. III. 60010
Edited by Claude A. Lucchesi
Tracing the Origin of Off-Flavors in a Breakfast Cereal During the routine quality assur ance examination of a packaged ready-to-eat breakfast cereal, a pineyspruce off-flavor was found. These quality assurance examinations rou tinely monitor all aspects of food products, such as package appearance, fill weight, product appearance, flavor, and odor, and usually total 25 or more attributes. These examinations or au dits of product quality are designed to locate problems in production that may go unnoticed for some period of time if they are not monitored. They usually are most important in locating subtle, esthetic quality differences which, when absent or changed, will not present the food manufacturer's best tasting product to the consumer. The observation of this piney off-fla vor in the cereal product was very im portant since subsequent taste panels showed that it contributed a highly
undesirable flavor character. Location of the source of this adverse flavor and its quick removal were of paramount importance because of present day methods of manufacturing large amounts of food products at a single location. Scheme A shows the steps taken to locate the piney off-flavor source. There were three possible sources: • The ingredients of the cereal product • The process, i.e., odor develop ment during cooking • The package or the external envi ronment. One advantage in the development of an analytical approach to this type of problem is that the off-flavor can be traced organoleptically with the nose as well as with analytical instru ments. In fact, the nose is probably the most important analytical tool an
Ingredients (No Piney Odors)
Process (No Piney Odors)
Base Paper (Papery)
'—ι — Packaged Finished Product (Piney OffFlavor)
P
—
Micro
Outer Box
I (Inky)
I
Wax
1 (Waxy-Oily)
Package
I
I
,
—ι Inner Liner
Scheme A. Odor source of piney off-flavor Odor descriptions in parentheses
ι
, Paraffin Wax
analytical flavor chemist uses. Each of the ingredients used in the cereal manufacture was smelled, and no source of piney odor was found. The processing system, especially the water sources, was examined, and no piney odor source found. This was probably the least likely source of the off-flavor but could not be ruled out completely until the system was checked. When the packaging material used for the outer boxes was exam ined, it was not piney but the inner glassine liner contained a piney odor. A similar procedure was used to find the piney source in the components of the glassine liner. The liner is com posed of two sheets of Kraft paper laminated with a resin in microcrystalline wax and overwaxed on both sides with paraffin wax. As seen in Scheme A, the resin used in bonding the paper layers is the obvious culprit. Since the resin contains an odorous material, the method of choice for iso lation of these components was a dis tillation technique. Vacuum distilla tion of the resin at 175 °C and 0.5-μ pressure was used to strip the volatile odor from the resin, and collection of the volatiles was accomplished in coldfinger traps cooled with dry ice-ace tone baths. The collected volatile material was rinsed from the traps with pentane, and the resulting solution produced the typical piney odor that was noted in the glassine liner and off-flavored product when examined organolepti cally on perfume blotters (thick filter paper). To determine precisely what chemi cal components were responsible for the off-flavor, a further fractionation of the distillate was undertaken (Scheme B). Again, with organoleptic evaluation as the criteria for following the piney off-flavor, gas chromatogra phy was used to fractionate the com ponents into discrete flavor entities. Gas chromatography was carried out
ANALYTICAL CHEMISTRY, VOL. 49, NO. 11, SEPTEMBER 1977 · 901 A
Volatiles Distillate (Piney)
GC Odor Gram
8 Piney Components
Odor Importance
Component Identification
Scheme B. Evaluation of individual component/odor importance
on a Carbowax 20M column, and the separate components were organoleptically evaluated at the end of the column. The use of 3/1 exit splitter attached to a heated collection vent and exit sniffing port allowed each component to be organoleptically evaluated as it exited from the column. From the chromatogram (Figure 1), at least nine of the separated peaks, including most of the major peaks, had odors associated with a piney character. Since more than one component had piney character, the identity of the piney odor components was needed to evaluate their individual thresholds. GC-MS analysis yielded the component identifications shown in Table I. All the components identified were common to pine oil or could be derived via hydrogénation of pine oil during resin processing and had published odor thresholds in the 1 to 8ppbrange (/).
•^
Jr.
Piney Liner
M
At this point, even with the identities established, it was not known which of these components had a pronounced flavor effect in the finished product. Several avenues were now available to determine which of the chemicals or group of components were responsible for the off-flavors. Since there are ranges of flavor thresholds covering six orders of magnitude, it is not a safe assumption to regard the most abundant as the most odorous. One approach would be to obtain each of the chemicals and determine their odor thresholds in the product. Then one must determine the amount of transfer from the package to the product and limit the package to those levels or below for complete flavor compatibility. This would be a long and time-consuming task that would not necessarily yield any more practical results than the alternate approach we chose to use. The
No
Odor
J Wpak " Piney
M
objective of our approach was to develop an appropriate quality control method and define specification limits for the purchase of the waxed glassine liner material. Since the ultimate desire was to prevent odor/flavor transfer to the product, we took advantage of this transfer property to help define the specification limits of the piney odor components. To develop the appropriate flavorinstrumental correlations as outlined in Scheme C, samples of waxed glassine with varying levels of pine odors were subjected to organoleptic analysis for their ability to produce off-flavor in ready-to-eat cereals. They were ranked by a panel of expert judges into two classes: acceptable (no foreign flavor imparted) and unacceptable (definite foreign odor or flavor) resulting in substandard finished product. The latter category was subdivided into levels designated as weak,
GC Comparison
Qualitative Profiles
Strong I Piney
Scheme C. Determination of component limits in glassine liner for product compatibility 902 A · ANALYTICAL CHEMISTRY, VOL. 49, NO. 11, SEPTEMBER 1977
Quantitate
Specification Limits
DIAL A , COLUMN
Table I. Component Identifications Figure 1 pk. no.
Odor
14 15 16
Weak pine Weak pine Slightly strong pine Pine tree Camphor Camphor Fragrant Sweet, pleasant Sour, camphor Very strong pine Licorice Fatty-citrus Flowery, green Pine, chestrub, strong Resinous, pine pitch Foul, acidic
Identification by GC-MS
Menthane Menthane Camphene 8-p-Menthene Limonene 1,8-Cineot P-cymene 1,4-p-Menthadiene Camphor Fenchyl alcohol p-lsopropyl anethole Borneol Borneol acetate
Retention time of authentic compound
+ +
+
* + · authentic compound matches unknown retention time. Others were not compared or not available. sH~!*in!
a.
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