Characterization of the aroma compounds in crystal malt

Crystal malt, the most popular type of specialty malt used in beer brewing, plays a vital role in forming complex flavor and color. Nevertheless, crystal malt is only defined based on the malting process, and there is not any standard to evaluate its quality. In the current study, the volatile aroma constituents of commercial crystal malt samples were analyzed with headspace solid-phase microextraction combined with gas chromatography-mass spectrometry, in order to explore the characteristic aroma compounds of crystal malt. The average concentration of volatile aroma compounds in 10 crystal malt samples is 587 µg L^-1 , ranging from 347 to 1265 µg L^-1 . A total of 38 aroma compounds were identified, 47% of which were existed in all the 10 samples. Based on principal component analysis and odor activity value, isobutyraldehyde, 2-methylbutanal, furfural, 2-acetyl-1H-pyrrole, oct-1-en-3-ol, 4-methyl-2-phenyl-2-pentenal, and (2E)-2-isopropyl-5-methyl-2-hexenal could be considered the characteristic aroma compounds of crystal malt. The results of this present study would help to establish a standard to assess the quality traits of crystal malt sample.

Identification of potential odorant markers to monitor the aroma formation in kilned specialty malts

Specialty malts are strategic ingredients regarding their contribution to colour and flavour of beer. Malts with the same colour may present distinct flavour characteristics and intensities. Contradictorily, colour is the benchmark in practical quality control. To investigate the correlation between colour and flavour of kilned barley specialty malts, odorants of commercial products of pale ale (5-9 EBC), Vienna (6-10 EBC), Munich (11-35 EBC) and melanoidin malts (80-90 EBC) were screened via solvent-assisted flavour evaporation (SAFE) and compared via comparative aroma extract dilution analysis (cAEDA). Subsequently, selected odorants were quantified using solid-phase microextraction (SPME). A total of 34 odorants were detected, of which 12 exhibited a concentration increase as the coloration increased, whereas 4 suggested the influence of temperature and modification degree on aroma formation. Such odorants are thus elected as potential markers for monitoring the influence of process variations on the formation of aroma in commercial kilned specialty malts.

Uncovering aroma boundary compositions of barley malts by untargeted and targeted flavoromics with HS-SPME-GC-MS/olfactometry

In this study, HS-SPME/GC-MS based untargeted and targeted flavoromics combing with olfactometry were employed to uncover aroma boundary compositions of five types of commercial barley malts with a wide range of Lovibond (L), including kilned base malts (1.8 L and 3.5 L) and roasted caramel malts (10 L, 60 L, and 120 L). Thirty-two compounds were identified as aroma-active with modified detection frequency (MF) > 50%. 3-Methylbutanal (malty), (2E)-nonenal (fatty, cardboard-like), and 2-furfural (burnt, bready) were recognized as the most influential odorants with MF > 70% in all the malts. After untargeted flavoromics, twenty-eight aromas were retained and quantitated. Furthermore, aroma boundary compositions inside/among malt groups were explored with PLS-DA. Eight aroma markers, 3-methylbutanal, 2-isopropyl-5-methyl-2-hexenal, (2E,4E)-Decadienal, 2-furfual, maltol, 2-acetylpyrrole, phenylacetaldehyde, and ethyl hexadecanoate were shortlisted for aroma boundary compositions regarding to the Lovibond of malts.

Aroma and color development during the production of specialty malts: A review

Specialty malts comprise a promising field for innovative approaches concerning their potential in terms of color, aroma, and taste influence on the composition of beer and other beverages. Nevertheless, poor reproducibility of aroma and taste is a recurrent struggle between maltsters, leaving color as a practical parameter for quality control. However, malts with similar coloration can present distinct aroma profiles, leaving open questions concerning key aroma compounds, their dynamic responses to malting process variations and to what extent they may vary in a certain color range. Key aroma volatiles have been identified in the matrix of barley malt, comprising a variety of products of non-enzymatic browning reactions (e.g., caramelization, pyrolysis, and Maillard reactions). Here, water plays a crucial role together with the intensity of the temperature regimes. Nevertheless, the final aroma profile of a malt product is the result of a balance between aroma formation and losses. Therefore, the correlation between color and aroma is of big complexity. That being the case, the present article questions if key aroma compounds responsible for the peculiar flavors of specialties have been defined by scientific literature and whether their production dynamics is unveiled. In this manner, this work proposes an overview of the aroma compounds present in specialty malt products studied up to the current date. More specifically, the process production of specialty malts and its potential impact on the formation of aroma and taste is studied alongside the key aroma-active compounds, their correlation to color, and trending analytical techniques for aroma and color assessment.

Relationships between antioxidant activity, color, and flavor compounds of crystal malt extracts

Aqueous extracts were prepared from five barley crystal malts (color range 15-440 degrees EBC, European Brewing Convention units). Antioxidant activity was determined by using the 2,2'-azinobis(3-ethylbenothiazoline-6-sulfonic acid) (ABTS(*)(+)) radical cation scavenging method. Antioxidant activity increased with increasing color value although the rate of increase decreased with increasing color value. Color was measured in CIELAB space. Extracts of the 15, 23, and 72 degrees EBC malts followed the same dilution pathway as did the 148 degrees EBC sample at higher dilution levels, indicating that they could each be used to give the same color by appropriate dilution. The 440 degrees EBC sample followed a different dilution pathway, indicating that different compounds were responsible for color in this extract. Fifteen selected volatile compounds were monitored using gas chromatography/mass spectrometry (GC/MS). Levels of methylpropanal, 2-methylbutanal, and 3-methylbutanal were highest for the 72 degrees EBC sample. When odor threshold values of the selected compounds were taken into account, 3-methylbutanal was the most important contributor to flavor. Relationships between levels of the lipid oxidation products, hexanal and (E)-2-nonenal, and antioxidant activity were complex, and increasing antioxidant activity for samples in the range of 15-148 degrees EBC did not result in reduced levels of these lipid-derived compounds. When different colored malt extracts were diluted to give the same a* and b* values, calculated antioxidant activity and amounts of 3-methylbutanal, hexanal, and (E)-2-nonenal decreased with increasing degrees EBC value.

Thermal degradation of precursors and formation of flavour compounds during heating of cereal products. Part II. The formation and changes of volatile flavour compounds in thermally treated malt extracts at different temperature and pH1

The effect of temperature and pH on the formation and changes of volatile flavour compounds in thermally treated malt extracts was studied. The dependence of thermal treatment parameters on organoleptic properties of the extracts was stated. Alkaline pH of the medium was found to promote the formation of the compounds yielding a caramel odour. The most desirable organoleptic characteristics were obtained at pH 4.0-5.5 and temperature 140 degrees C. Thirty compounds typical for nonenzymatic browning were identified.