Curie-point pyrolysis-capillary gas chromatography-high-resolution mass spectrometry of microcrystalline cellulose

Furan represent a class of compounds that have been reported in a wide variety of foods. Normally, they result from thermal decomposition reactions, and, as such, are important in foods. They also possess unique sensory properties and, thus, can significantly contribute to food flavor. This review shall attempt to summarize their food occurrences, organoleptic properties, and formation pathways.

Furans in foods

A highly characteristic and often undesirable flavor associated with soy protein materials largely explains the slower‐than‐expected progress over recent years in the development of high‐protein foods based on soya. Apart from the inherent flavor of the bean, different flavors are produced on processing and on storage. Major problems are the absence of an attractive positive flavor, the presence of off‐flavors of several kinds, the tenacious binding of such flavors to the soy protein molecules, and the difficulties of removing and/or masking these unacceptable qualities. This review provides a reappraisal of current literature evidence relating to each of these aspects and summarizes published patents of processes for soy flavor improvement.

Soy flavor and its improvement

Furan has recently received attention as a possibly hazardous compound occurring in certain thermally processed foods. Previous model studies have revealed three main precursor systems producing furan upon thermal treatment, i.e., ascorbic acid, Maillard precursors, and polyunsaturated lipids. We employed proton transfer reaction mass spectrometry (PTR-MS) as an on-line monitoring technique to study furan formation. Unambiguous identification and quantitation in the headspace was achieved by PTR-MS/gas chromatography-mass spectrometry coupling. Ascorbic acid showed the highest potential to generate furan, followed by glyceryl trilinolenate. Some of the reaction samples generated methylfuran as well, such as Maillard systems containing alanine and threonine as well as lipids based on linolenic acid. The furan yields from ascorbic acid were lowered in an oxygen-free atmosphere (30%) or in the presence of reducing agents (e.g., sulfite, 60%), indicating the important role of oxidation steps in the furan formation pathway. Furthermore, already simple binary mixtures of ascorbic acid and amino acids, sugars, or lipids reduced furan by 50-95%. These data suggest that more complex reaction systems result in much lower furan amounts as compared to the individual precursors, most likely due to competing reaction pathways.

Quantitation of furan and methylfuran formed in different precursor systems by proton transfer reaction mass spectrometry.

Current information relating to the chemical composition of both natural and simulated meat flavors is presented, with particular reference to beef flavor. The origin of natural meat flavor is described in terms of the nature of the precursors and the formation pathways of volatile components contributing to meat flavor. A table listing the aroma components of natural beef is included and their relative contributions to the overall flavor is considered. The historical development of commercial meat flavorings is traced from the early spice blends and meat extracts to the thermally produced imitation meat flavors (processed meat flavorings) including “reaction products” and flavorings derived from natural meat. Some G.B. and U.S. “reaction products” patents and meat flavor contributing compounds patented since 1960 are summarized in tabular form.

Natural and simulated meat flavors (with particular reference to beef)

SUMMARY— Volatiles from anhydrous glucose heated in air at 25OT for 30 min were collected in a trap maintained at the temperature of solid carbon dioxide. A concentrated ether extract of the distillate was shown by gas chromatography to contain at least 100 compounds. Among those identified and heretofore unreported from heated glucose were the gamma lactone of 4-hydroxy-2-pentenoic acid, l-(2′-furyl)-propane-1,2-dione (acetylfuroyl), 3-methylcyclopentane-1,2-dione, phenol and methylfuroic acid.

Volatile Compounds from‐ Heated Glucose

SUMMARY

During low temperature pyrolysis (under 200°C). the disappearance of glucose and pH change of an aqueous solution of the pyrolyzate were found to approximate first order reactions. Since change of concentration of glucose and change of pH are directly related to time, the mathematical equations describing the two occurrences were combined through this common variable. The resulting equation describes the residual concentration of glucose as a function of change of PH.

R. H. Walter

Papers

Volatile Compounds from‐ Heated Glucose

RATES OF pH CHANGE AND DISAPPEARANCE OF GLUCOSE DURING LOW TEMPERATURE PYROLYSIS