Jane K. Parker

Kinetic model for the formation of acrylamide during the finish-frying of commercial French fries

Acrylamide is formed from reducing sugars and asparagine during the preparation of French fries. The commercial preparation of French fries is a multistage process involving the preparation of frozen, par-fried potato strips for distribution to catering outlets, where they are finish-fried. The initial blanching, treatment in glucose solution, and par-frying steps are crucial because they determine the levels of precursors present at the beginning of the finish-frying process. To minimize the quantities of acrylamide in cooked fries, it is important to understand the impact of each stage on the formation of acrylamide. Acrylamide, amino acids, sugars, moisture, fat, and color were monitored at time intervals during the frying of potato strips that had been dipped in various concentrations of glucose and fructose during a typical pretreatment. A mathematical model based on the fundamental chemical reaction pathways of the finish-frying was developed, incorporating moisture and temperature gradients in the fries. This showed the contribution of both glucose and fructose to the generation of acrylamide and accurately predicted the acrylamide content of the final fries.

Sensory and instrumental analysis of medium and long shelf-life Charentais cantaloupe melons (Cucumis melo L.) harvested at different maturities

Highlights • Flavour of medium and long shelf-life Charentais cantaloupe melons was compared.• Volatile and semi-volatile profiles were correlated with sensory data using multifactorial analysis.• Maturity at harvest has a significant impact on the flavour of medium-shelf life fruit.• Maturity at harvest had much less impact on a long shelf-life genotype.• Esters and sulphur-compounds were more abundant in mature medium shelf-life fruit.

Kinetic modeling of the generation of 2- and 3-methylbutanal in a heated extract of beef liver.

Quantitative control of aroma generation during the Maillard reaction presents great scientific and industrial interest. Although there have been many studies conducted in simplified model systems, the results are difficult to apply to complex food systems, where the presence of other components can have a significant impact. In this work, an aqueous extract of defatted beef liver was chosen as a simplified food matrix for studying the kinetics of the Maillard reaction. Aliquots of the extract were heated under different time and temperature conditions and analyzed for sugars, amino acids, and methylbutanals, which are important Maillard-derived aroma compounds formed in cooked meat. Multiresponse kinetic modeling, based on a simplified mechanistic pathway, gave a good fit with the experimental data, but only when additional steps were introduced to take into account the interactions of glucose and glucose-derived intermediates with protein and other amino compounds. This emphasizes the significant role of the food matrix in controlling the Maillard reaction.

Effects of plant sulfur nutrition on acrylamide and aroma compounds in cooked wheat.

Wheat flour from plants deficient in sulfur has been shown to contain substantially higher levels of free amino acids, particularly asparagine and glutamine, than flour from wheat grown where sulfur nutrition was sufficient. Elevated levels of asparagine resulted in acrylamide levels up to 6 times higher in sulfur-deprived wheat flour, compared with sulfur-sufficient wheat flour, for three varieties of winter wheat. The volatile compounds from flour, heated at 180 degrees C for 20 min, have been compared for these three varieties of wheat grown with and without sulfur fertilizer. Approximately 50 compounds were quantified in the headspace extracts of the heated flour; over 30 compounds were affected by sulfur fertilization, and 15 compounds were affected by variety. Unsaturated aldehydes formed from aldol condensations, Strecker aldehydes, alkylpyrazines, and low molecular weight alkylfurans were found at higher concentrations in the sulfur-deficient flour, whereas low molecular weight pyrroles and thiophenes and sugar breakdown products were found at higher concentrations in the sulfur-sufficient flour. The reasons for these differences and the relationship between acrylamide formation and aroma volatile formation are discussed.

The kinetics of thermal generation of flavour

Control and optimisation of flavour is the ultimate challenge for the food and flavour industry. The major route to flavour formation during thermal processing is the Maillard reaction, which is a complex cascade of interdependent reactions initiated by the reaction between a reducing sugar and an amino compound. The complexity of the reaction means that researchers turn to kinetic modelling in order to understand the control points of the reaction and to manipulate the flavour profile. Studies of the kinetics of flavour formation have developed over the past 30 years from single- response empirical models of binary aqueous systems to sophisticated multi-response models in food matrices, based on the underlying chemistry, with the power to predict the formation of some key aroma compounds. This paper discusses in detail the development of kinetic models of thermal generation of flavour and looks at the challenges involved in predicting flavour.

Whey protein mouth drying influenced by thermal denaturation

Whey proteins are becoming an increasingly popular functional food ingredient. There are, however, sensory properties associated with whey protein beverages that may hinder the consumption of quantities sufficient to gain the desired nutritional benefits. One such property is mouth drying. The influence of protein structure on the mouthfeel properties of milk proteins has been previously reported. This paper investigates the effect of thermal denaturation of whey proteins on physicochemical properties (viscosity, particle size, zeta-potential, pH), and relates this to the observed sensory properties measured by qualitative descriptive analysis and sequential profiling. Mouthcoating, drying and chalky attributes built up over repeated consumption, with higher intensities for samples subjected to longer heating times (p < 0.05). Viscosity, pH, and zeta-potential were found to be similar for all samples, however particle size increased with longer heating times. As the pH of all samples was close to neutral, this implies that neither the precipitation of whey proteins at low pH, nor their acidity, as reported in previous literature, can be the drying mechanisms in this case. The increase in mouth drying with increased heating time suggests that protein denaturation is a contributing factor and a possible mucoadhesive mechanism is discussed.

Introduction to aroma compounds in foods

Aroma conveys the essential character of food and provides variety and interest to what we consume. The aim of this chapter is to provide an overview of the structure, aroma and occurrence of different classes of aroma compounds typically identified in food products, highlighting character impact compounds in some of the major food categories. It begins with an overview of sensomics, arguably the most effective method used to identify which compounds contribute to the aroma profile of food and beverages, and defines the standard terminology that is used in the discussion of odour-active compounds that follows.

Thermal generation or aroma

Abstract Thermal processing is the major source of aroma for all cooked foods. Aroma can be derived from amino acids and sugars via the Maillard reaction, from lipid oxidation, or from the thermal breakdown of other components of the food such as ascorbic acid, thiamine, ferulic acid and carotenoids. These pathways are interrelated, and are reviewed, in turn, with the emphasis on the Maillard reaction, considering it also as a source of taste compounds and antioxidants as well as potentially harmful products. Strategies to optimise the desirable flavour attributes whilst minimising undesirable aspects are discussed, and the role of the Maillard reaction in the development of process flavours for the snack industry, and their legal status under recent EU regulations, is deliberated.

Aroma formation in beef muscle and beef liver

Beef muscle and beef liver were used as matrices in which to observe the Maillard reaction. Samples were spiked with glucose, ribose, glycine or cysteine and the effect on the formation of pyrazines and furanthiols was studied. The addition of glucose showed that glucose limited the formation of pyrazines in muscle but not in liver. The addition of glycine demonstrated how some pyrazines were reliant on glycine for their formation whereas others were not, confirming reported reaction mechanisms from in model systems. The addition of cysteine showed that in muscle the availability of H2S was the limiting step in the formation of 3-methyl-2-furanthiol (MFT) whereas in liver, MFT could not be detected in any of the systems. This could be due to the absence of ribose in liver, but may also indicate the presence of interactions with the liver matrix.

Development of a Zeolite Filter for Removing Polycyclic Aromatic Hydrocarbons (PAHs) from Smoke and Smoked Ingredients while Retaining the Smoky Flavor

The popularity of smoked foodstuffs such as sauces, marinades, and rubs is on the rise. However, during the traditional smoking process, in addition to the desirable smoky aroma compounds, harmful polycyclic aromatic hydrocarbons (PAHs) are also generated. In this work, a selective filter was developed that reduces PAH concentrations in a smoke by up to 90% while maintaining a desirable smoky flavor. Preliminary studies using a cocktail of 12 PAHs stirred with a zeolite showed the potential for this zeolite to selectively remove PAHs from a simple solution. However, pretreatment of the smoke prior to application removed the PAHs more efficiently and is more widely applicable to a range of food ingredients. Although volatile analysis showed that there was a concomitant reduction in the concentration of the smoky compounds such as 2-methoxyphenol (guaiacol), 2-methylphenol ( o-cresol), and the isoeugenols, sensory profiling showed that the difference in perception of flavor was minimal.