LAGER-TYPE BEER MADE FROM EXTRUDED MALT; SENSORY AND CHEMICAL ANALYSES

A lager-type beer was brewed from a mixture of partially dried green malt and extruded green malt (9:1). Small flavour differences were observed in the beer made from the extruded malt when compared with two other types of beer, namely standard lager and beer made from 100% green malt which was partially dried. More than 90 flavour components were described upon sniffing of the GC eluate. Most of them were present in trace amounts which did not allow their identity to be established. However, in all beer samples several unidentified components were described as giving a “roasted”, “burnt”, “bread crust” or “biscuit” odour. These odour characteristics probably derive from the alkylpyrazines present. Positively identified pyrazines were only found in the “extruded” beer, namely methylpyrazine and 2,5 (and/or-2,6)-dimethylpyrazine. However, when the beer was tasted, no characteristics associated with a roasted or burnt flavour were registered. Among the identified flavour components esters and alcohols were abundantly represented.     

A MICROBIOLOGICAL EVALUATION OF BARLEY MALT PRODUCTION

The development of the microflora of barley malt was examined by direct and dilution plating. At all stages of the malting process mesophilic bacteria predominated. Viable counts of bacteria on green malt were 85–600 times greater than on the original barley, but fell to less than one-half of the original level with kilning. Corresponding increases in yeast and, especially, mould counts during malting were smaller. The yeast-like mould Geotrichum candidum was prominent in green malt. Although counts of yeasts and most moulds were considerably reduced by kilning, Mucor spp. proliferated during kilning.     

Dissimilarity scaling and INDSCAL analysis in the study of flavour differences between normal pHu and DFD beef

Overall dissimilarity measurement of paired stimuli followed by Individual Differences Scaling (INDSCAL) analysis was used to study flavour perception in a set of beef extracts. The experiment was designed to determine whether pH contributed to flavour difference between beef of “normal” ultimate pH (pHu5.8) and “dark-cutting” (DFD) beef (pHu6.2). Assessors distinguished the flavour of “normal” pHu and DFD beef both by a combination of pH and titratable acidity, and a second dimension independent of pH. The chemicals added to adjust pH independently of the original muscle composition contributed a third flavour dimension. Substantial assessor variation was observed in the relative weight given to the three flavour dimensions, and this is discussed in relation to the task of judging overall dissimilarity.     

DIMETHYL TRISULPHIDE,ITS MECHANISM OF FORMATION IN HOP OIL AND EFFECT ON BEER FLAVOUR

The precursor of dimethyl trisulphide (DMTS) in hops is destroyed by sulphur dioxide during kilning, but then re-forms slowly during storage. A redox mechanism is suggested and S-methyl-cysteine sulphoxide is postulated as the DMTS-precursor. The effect of DMTS on beer flavour is described. The flavour threshold value for DMTS in a commercial beer has been found to be 0·10μg/litre.     

EFFECT OF KILNING ON MALT STARCH AND ON THE DEXTRIN CONTENT OF RESULTING WORTS AND BEERS

Examination of starches separated from green malt and from kilned malts of colour ranging between 3 and 23 shows that only small amounts of “new” carbohydrate linkages are formed in the starches during kilning, though the colour changes from white to buff and the amount of contaminating protein increases. Nevertheless, standard enzymic treatments show that the higher the colour value of the malt, the less susceptible it is to attack by amylases, and the larger is the content of non-fermentable, non-dialysable dextrin. Although the amount of non-dialysable dextrin rises as the colour value of the malt increases, dextrin content of the derived wort is not directly related to the enzymic activity of the malt. Thus, the non-fermentable dextrin of wort from malt of colour 3 is little higher than that of wort from green malt, despite the considerably higher diastatic power of the latter. Head retention values of draught and bottled beers from the green malt and kilned malts of colours 3, 6 and 13 show no correlation with dextrin content.     

Relating consumer preferences to sensory attributes of instant coffee

The sensory profiles of 11 instant coffees including pure coffees (PC), coffee blends (CB) and a chicory instant drink (CID), commercially available in South Africa, were described and quantified. These were then related to consumer preferences (n=199) for the instant coffees using preference mapping. Based on consumer preferences, four consumer groups were identified, “pure coffee lovers” (23%), “coffee blend drinkers” (30%), “general coffee drinkers” (37%) and “not serious coffee drinkers” (10%). The “pure coffee lovers” prefer the more astringent, bitter, roasted, nutty and full-bodied flavour of the pure coffee samples. The less intense coffee flavour character, but higher sweetness and root flavour, typical of chicory blended instant coffee, were attributes that were preferred by the “coffee blend lovers”. The “general coffee drinkers” seem to consume coffee out of habit and are less concerned about the specific sensory properties of the coffee.     

Use of healthier fats in biscuits (olive and sunflower oil): changing sensory features and their relation with consumers' liking

The aim of this study was to evaluate consumer acceptability of biscuits when saturated fat was replaced by olive or sunflower oil and to determine the sensory characteristics responsible for changes in acceptability. Ninety seven consumers evaluated the acceptability of six biscuit samples varying in the fat source (dairy shortening, olive oil and sunflower oil) and fat content (10.6% and 15.6%). Using a Check All That Apply question (CATA), consumers also evaluated sensory properties of biscuits. Results indicated that the replacement of saturated fat (dairy shortening) by vegetable oils had an effect on biscuit acceptability which depended on biscuit fat content. According to biscuits' acceptability data, three different clusters of consumers were identified. By using a multiple factor analysis, the relationship among sensory CATA data and acceptability of each cluster explained the different acceptability patterns of consumers. For most of consumers acceptability was related to attributes “crispy”, “easy to chew” and “biscuit flavour” which, for one group were perceived in shortening biscuits and, for another in both olive and shortening biscuits. However, for the third group of consumers, acceptability was only related to flavour attributes like “roasted flavour” or “biscuit flavour” that were perceived in vegetable oil biscuits which were the preferred biscuits while, shortening biscuits were disliked and perceived as having an “off flavour”.     

ACTIVITIES OF VARIOUS PEPTIDASES IN BARLEY,GREEN MALT AND MALT

The three groups of malt peptidases (carboxypeptidases, “naphthylamidases” and (amino) peptidases acting on Leu-Tyr and Ala-Gly) are present in unmalted barley; the activities are low and of a similar order of magnitude. On germination the activities of the different carboxypeptidases increase from 10- to 20-fold; the “naphthylamidases” increase only 2-fold, and the peptidase activities increase from 3- to 6-fold. None of these enzymes is inactivated during kilning to any significant extent. There are considerable differences between the carboxypeptidase activities of malts derived from different varieties of barley and the activities are correlated with α-amylase activity.     

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

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.     

THE FLAVOUR OF BEER—A REVIEW*

Following a general consideration of the chemical nature of compounds which provide sensations of taste or of odour, the flavour components of beer are discussed in some detail. Methods suitable for determining individual flavour compounds are indicated in relation to organoleptic assessment by a selective panel of testers. The concept of “flavour index” (flavour threshold of a component divided by the concentration of that component in beer) is introduced: substances with a low flavour index require close control in the production of beer.     

DIMETHYL SULPHIDE AS A FEATURE OF LAGER FLAVOUR

Dimethyl sulphide is a normal flavour component of many lagers, particularly Continental lagers, but is not present in ales in sufficient quantity to affect flavour. The kilning stage of malting determines the extent to which a precursor capable of being converted to dimethyl sulphide by yeast will be present in wort. Worts prepared from Continental malts appear to contain more of this precursor than worts from British malts and the derived beers thus contain more dimethyl sulphide. Amounts of dimethyl sulphide formed from the precursor during fermentation depend on the strain of yeast employed, whilst the amounts retained in solution depend on physical factors such as temperature and rate of evolution of carbon dioxide.     

Flavour-encapsulation and flavour-release performances of a commercial yeast-based delivery system

Empty yeast cells are used as a thermo-stable delivery system for flavour encapsulation. The flavour encapsulation efficiency was assessed regarding flavour molecule properties. A model based on passive transfer demonstrated the selectivity of the external cell wall and the attractive role of the internal yeast plasma membrane (phospholipid bi-layer). Not all the molecules can penetrate inside the yeast. Selection is based on the hydrophobic properties. The efficiency of encapsulation is higher than 50% for flavour compound log P higher than 2.0.Flavour release mechanism from yeast cells was characterized using a series of analytical techniques and limonene was used as a model representing a hydrophobic flavour. Dry loaded cells immersed “in water” or “in oil” or “in water and then in oil” showed different behaviours regarding the release performances leading to the careful study of the encapsulation barrier properties. Water is needed for release to occur. The modelling of the drying of the cell wall was consistent with a huge kinetic hysteresis between water sorption and water desorption isotherms. This also explained the unexpected reduction of the cell wall permeability as a function of temperature and water loss. Among others, these conditions insure flavour protection during specific application in cooking processes. Furthermore, organoleptic tests showed higher scores than conventional spray dry powders in battered products and in instant noodles, as expected from the stability conditions investigated.     

四川风鸭呈味物质形成机理初探

本文对四川风鸭加工过程中的呈味物质进行了初步探讨,从而研究风鸭呈味物质的形成机理.结果表明:脂肪氧化和蛋白质分解是形成风鸭风味的主要途径,游离脂肪酸和游离氨基酸是构成风鸭风味的重要前体物质.四川风鸭主要呈味物质的形成在"腌制"到"风干6天"这段时期.四川风鸭呈弱酸性.风鸭的风味物质中,脂肪氧化产物主要以羰基类物质形式存在.油酸、棕榈酸、亚油酸、谷氨酸、天门冬氨酸、精氨酸是风鸭风味的主要呈味物质.     

DERIVATION OF A PROFILE METHOD FOR SENSORY ANALYSIS OF BEER FLAVOUR

Flavour assessment ultimately depends on sensory methods of analysis. Profile methods are considered to offer the best current solution to the problem of describing, and as far as possible quantifying, beer flavour. The sensory characteristics of flavour must be identified and described systematically and objectively, without prejudice due to preferences. A flavour ‘vocabulary’ is needed which is applicable to all types of beer. This involves selection of significant terms which have the same meaning for different people. Any system universally applicable to all types of beer must necessarily be complex, but such a “universal” system is essential for research. It also provides a “dictionary” from which terms can be selected for simpler profiles for quality control of particular products. The steps in the development of a profile system are described. Development has depended and will continue to depend on the collaboration of a large number of individuals and groups of people within the industry. Profile systems cannot be static but must continuously evolve.     

Effect of starter species on the content of some volatile aromatic compounds of kashkaval “Balkan” and kashkaval “Vitosha”

Four kinds of starter cultures created in this country were used for production of kashkaval “Vitosha” and kashkaval “Balkan”. In the process of ripening and storage of the products the changes of some aroma compounds taking part in flavour formation were followed besides acidity, pH and percentage of sodium chloride. Two of the aroma compounds, i.e. diacetyl and ethanol, were of outstanding importance for the quality of kashkaval “Vitosha”, whereas in respect to kashkaval “Balkan” such a relationship was not established. Inference was drawn that the product's flavour was dependent on starter culture and kind of milk.     

The application of multivariate mathematical-statistical methods to the solution of problems in nutrition theory,nutritional economics and food technology. Part 5. Cluster analysis as a tool for proofing sensory attributes

The task of the test program was the replacement of more subjective and time-consuming sensory methods by instrumental or chemical ones. In the case of meat flavour concentrates (MFC) and their burnt-bitter flavour the cluster analysis resulted in the following: –The test program was based on 20 samples produced by statistical plans (central composite design for 3 explanatory variables). Starting with 10 sensory and 40 instrumental methods the latter have been reduced to 10 methods considering the suppositions for application of the cluster analysis. –The 20 samples were tested on one side by a trained sensory panel for the intensity of the “burnt-bitter” flavour and parallely by the selected 10 instrumental values. This resulted in both cases in the differentiation into 3 clusters with significant differences. –For evaluation of MFC as to their “burnt-bitter” flavour it was shown that the sensory evaluation can be replaced or supported by analytical data successfully. Thus cluster analysis is a useful tool for this purpose delivering transparent results.