Conor M. Delahunty

Descriptive sensory analysis: past, present and future

Abstract Descriptive sensory analyses are distinguished from other sensory testing methods in that they seek to profile a product on all of its perceived sensory characteristics. In this paper, the process of implementing a descriptive sensory programme will be reviewed, with some discussion of new approaches and applications. Variations of descriptive sensory analysis will also be considered, including The Flavour Profile Method™, Texture Profile Method™, Quantitative Descriptive Analysis™, Quantitative Flavour Profiling, Spectrum™ method and Free-Choice Profiling. Advantages and disadvantages of these methods will be discussed in a comparative way and the future of descriptive sensory analysis is also considered. In addition, some current assumptions of sensory panel training are questioned and potential new applications of descriptive techniques are discussed.

Oral sensitivity to fatty acids, food consumption and BMI in human subjects

Fatty acids are the chemical moieties that are thought to stimulate oral nutrient sensors, which detect the fat content of foods. In animals, oral hypersensitivity to fatty acids is associated with decreased fat intake and body weight. The aims of the present study were to investigate oral fatty acid sensitivity, food selection and BMI in human subjects. The study included two parts; study 1 established in thirty-one subjects (29 (sem 1.4) years, 22.8 (sem 0.5) kg/m2) taste thresholds using 3-AFC (3-Alternate Forced Choice Methodology) for oleic, linoleic and lauric acids, and quantified oral lipase activity. During study 2, fifty-four subjects (20 (sem 0.3) years, 21.5 (sem 0.4) kg/m2) were screened for oral fatty acid sensitivity using oleic acid (1.4 mm), and they were defined as hypo- or hypersensitive via triplicate triangle tests. Habitual energy and macronutrient intakes were quantified from 2 d diet records, and BMI was calculated from height and weight. Subjects also completed a fat ranking task using custard containing varying amounts (0, 2, 6 and 10 %) of fat. Study 1 reported median lipase activity as 2 mumol fatty acids/min per l, and detection thresholds for oleic, linoleic and lauric acids were 2.2 (sem 0.1), 1.5 (sem 0.1) and 2.6 (sem 0.3) mm. Study 2 identified twelve hypersensitive subjects, and hypersensitivity was associated with lower energy and fat intakes, lower BMI (P < 0.05) and an increased ability to rank custards based on fat content (P < 0.05). Sensitivity to oleic acid was correlated to performance in the fat ranking task (r 0.4, P < 0.05). These data suggest that oral fatty acid hypersensitivity is associated with lower energy and fat intakes and BMI, and it may serve as a factor that influences fat consumption in human subjects.

Analysis of volatile flavour compounds by Proton Transfer Reaction-Mass Spectrometry: fragmentation patterns and discrimination between isobaric and isomeric compounds

Abstract The behaviour of 53 flavour compounds in Proton Transfer Reaction-Mass Spectrometry (PTR-MS) was investigated. Obtained spectra showed general rules on fragmentation patterns of alcohols, aldehydes, ketones and esters. Alcohols and aldehydes split off water while ketones hardly show any fragmentation. The mass fragments at m/z=55 and 69 are potential markers for the presence of aldehydes and mono-unsaturated alcohols. Esters hydrolyse dependent on the ratio of the carbon chain length of their alcoholic part vs. their acidic part. Although fragmentation of individual compounds generally complicates the headspace spectra of complex mixtures, it can provide relevant information on discrimination of isobaric and isomeric compounds.

Use of autolytic starter systems to accelerate the ripening of Cheddar cheese

Abstract The rapid release of intracellular enzymes due to autolysis of lactic acid bacteria in the cheese matrix post-manufacture is thought to play a role in the acceleration of cheese ripening. To investigate this hypothesis Cheddar cheese was manufactured using three related starter systems which varied with respect to their autolytic properties. Starter system A contained a blend of two Lactococcus lactis strains (223 and 227) which had a low level of autolysis. System B was identical to A but included an adjunct of a highly autolytic strain of Lactobacillus helveticus (DPC4571). System C consisted only of strain DPC4571 as starter. The cheeses were evaluated during ripening for key ripening indices including autolysis of starter cells by release of intracellular marker enzyme lactate dehydrogenase (LDH), composition, proteolysis and flavour development by descriptive sensory analysis. Populations of Lb. helveticus DPC4571 decreased rapidly in cheeses B and C and were not detected by 8 weeks. The level of starter culture autolysis proceeded in the order C≫B>A. Levels of proteolysis were elevated in cheeses B and C relative to A. Principal component analysis of the sensory data separated the character of cheese A from that of cheeses B and C. Cheeses B and C developed a unique ‘balanced’ ‘strong’ flavour early in ripening with a ‘caramel’ and ‘musty’ odour and ‘sweet’ ‘astringent’ flavour compared to cheese A. Hierarchical cluster analysis grouped C at 2 months with B at 6 and 8 months reflecting accelerated flavour development. Proteolytic and sensory data support the hypothesis that autolysis accelerates the rate of cheese ripening.

Sensory characterisation of cooked hams by untrained consumers using free-choice profiling

Abstract The sensory characteristics of 11 hams were measured by 18 untrained consumers using Free-Choice Profiling and the data were analysed by Generalised Procrustes Analysis. Each consumer expressed their preference as an additional question. The first three dimensions of the analysis accounted for 37.9, 9.0 and 7.8% of the consensus variance, respectively, and Analysis of Variance showed significant differences between hams on all three dimensions. To summarise the freely chosen descriptive vocabularies, and help characterise each ham, descriptors thought to have similar meaning were separately modeled by Principal Components Analysis and model-to-model distances within the sensory groups of appearance, texture and flavour were calculated using Soft Independent Modeling of Class Analogy. Wiltshire type hams appeared marbled and dark in colour, had a fibrous and chewy texture and a hammy and meaty flavour. A shoulder meat ham appeared processed, rubbery, plastic and moist, had a processed, rubbery, moist and strong structured texture and a processed flavour. Modern tumbled hams varied in sensory character between the Wiltshire and the shoulder hams, and their character was reflected by their price. Preference was expressed for the Wiltshire hams and the modern tumbled hams with Wiltshire-type character.

Relationships between the gross, non-volatile and volatile compositions and the sensory attributes of eight hard-type cheeses

Abstract Relationships between individual flavour attributes of eight hard-type cheeses and their volatile compounds, free amino acids (FAA), free fatty acids (FFA) and gross compositional constituents were determined. Relationships were also determined between individual texture attributes and gross compositional constituents. A trained panel of 15 assessors described the sensory characteristics of the cheeses using eight odour, twenty flavour, four appearance and nine texture attributes. Volatile compounds were isolated using a model-mouth device. FAA, FFA and gross compositional constituents were determined using standard methods. Relationships were determined by using partial least squares regression coupled with a new jack-knife method for identification and elimination of non-contributing variables. Eight flavour attributes were found to be correlated with subsets of volatile compounds, FAA, FFA and gross compositional constituents. For instance, the “nutty” flavour of Emmental was found to be positively correlated with the concentrations of propionic acid, ethyl acetate and 2-pentanone. “Nutty” flavour was negatively correlated with the concentrations of salt in moisture and pH 4.6-soluble nitrogen (pH 4.6-SN). Four texture attributes were correlated with subsets of gross compositional constituents. For example, “firmness” was positively correlated with concentrations of protein, calcium and phosphorous and negatively correlated with pH value and level of pH 4.6-SN.

Relationships between sensory attributes and the volatile compounds, non-volatile and gross compositional constituents of six blue-type cheeses

Abstract Relationships between odour and flavour attributes of six blue-type cheeses and their volatile compounds, free amino acids (FAA), free fatty acids (FFA) and gross compositional constituents were determined. Relationships were also determined between texture attributes and gross compositional constituents. Fifteen assessors described the odour, flavour, appearance and texture profile of cheeses. Volatile compounds were isolated using a model-mouth apparatus. FAA, FFA and gross compositional constituents were determined using standard methods. Using Partial Least Squares Regression two odour and five flavour attributes were found to correlate with subsets of volatile compounds, FAA, FFA and gross compositional constituents. For example, “mouldy” flavour was positively correlated with the concentrations of pH 4.6-soluble nitrogen and 2-pentanone, 2-heptanone, 2-octanone and 2-nonanone. Three texture attributes were found to correlate with subsets of gross compositional constituents. For example, “crumbly” texture was positively correlated with concentration of fat and protein and negatively correlated with levels of moisture in the non-fat substance and moisture.

Nuts Improve Diet Quality Compared to Other Energy-Dense Snacks While Maintaining Body Weight

Previous studies have reported that regular nut consumption reduces cardiovascular disease (CVD) risk and does not promote weight gain despite the fact that nuts are energy-dense. However, no studies have investigated the body composition of those regularly consuming nuts compared to similar intakes of other snacks of equal energy density. This parallel study (n = 118) examined the effects of providing daily portions (~1100 kJ/d) of hazelnuts, chocolate, or potato crisps compared to a control group receiving no snacks for twelve weeks. Effects on body weight and composition, blood lipids and lipoproteins, resting metabolic rate (RMR), appetite indices, and dietary quality were compared. At week 12, there was no significant difference in any of the outcome measurements between the groups except for dietary quality, which improved significantly in the nut group. Nuts can be incorporated into the diet without adversely affecting body weight and can improve diet quality.

Long-term consumption of high energy-dense snack foods on sensory-specific satiety and intake

BACKGROUND The sensory attributes of foods may have an important influence on intake because of sensory-specific satiety (SSS). Foods with high SSS may aid in body weight maintenance as a result of termination of consumption before metabolic satiety. No studies have investigated whether long-term exposure to a food might change SSS or how this affects food intake. OBJECTIVE The objective was to compare the effects of daily consumption of 3 energy-dense snack foods (hazelnuts, chocolate, and potato chips) for 12 wk on SSS and ad libitum intake during a tasting session. DESIGN One hundred eighteen participants took part in this randomized, controlled, parallel study with 4 arms: control group (no additional food) or ∼1100 kJ/d for each snack. SSS, food intake, and body composition were measured at baseline and at week 12. RESULTS Daily consumption of snacks for 12 wk resulted in a statistically significant reduction in SSS in all 3 snack groups (P = 0.015). However, no such changes were seen in the control group (P = 0.608). Ad libitum energy intake increased over the study during the tasting sessions for the snack food across all groups, including the control group (P = 0.039). Inverse associations were found between baseline SSS and BMI (P = 0.039), percentage body fat (P = 0.013), and fat mass (P = 0.004). CONCLUSION Habitual consumption of a high energy-dense snack food results in a decrease in SSS, which could lead to a higher energy intake of the snack. This trial was registered at www.anzctr.org.au as ACTRN12609000265279.

Examination of chemical irritation and textural influence on food preferences in two age cohorts using complex food systems

Abstract The changes to the chemical senses of taste and smell that accompany ageing are widely documented, and there has been some evidence that these changes may influence food preferences of the older consumer. However, little is known about the loss of function of the residual senses of texture and chemical irritant perception and how such losses influence food preferences. A consumer panel comprising a young (20–35 years) and an older (>65 years) age cohort was recruited and sensory tests were conducted to determine perceived intensity, preferences and the possibility of cross modal interaction between the sensory modalities of chemical irritation and texture. Liquid, semi-solid and solid food systems were studied to enable comparisons to be drawn. Older consumers were less capable of discriminating between chemical irritation and texture stimuli, indicating loss of sensory function, but there was indication that higher levels of chemical irritation were preferred among older consumers in some texture types.