What is Coffee Crema? Things you need to know. There have been numerous studies on how external elements affect a customer’s impression or experience of a cup of coffee. We know, for example, that the information consumers acquire prior to consuming a product has an impact on their expectations and, as a result, on how they perceive the product’s quality (Siegrist and Cousin, 2009; Lange et al., 2002). Sa’enz-Navajas et al. (2013) found that a consumer’s level of expertise influences their quality judgments.
Furthermore, when it comes to beverages, the material of the cup or glass that a customer uses has a significant impact on how they perceive and rate that beverage (Schifferstein, 2009; Wan et al., 2015). According to studies, the way food packaging is constructed can influence a variety of aspects of the eating experience (Schifferstein et al., 2013). For all of these reasons, it’s no surprise that crema affects the overall espresso flavor experience.
Main Contents
Crema’s Influence on Visual Perception
Researchers looked at the impact of crema amount on consumer impressions in a recent study by Labbe et al. (2016). Consumers rated products in three ways in this study: (1) visually, with researchers assessing the expectations generated by visual cues, (2) in a “blind” condition, with all visual cues suppressed and researchers assessing in-mouth perception, and (3) by taste and sight, with consumers evaluating the coffee in a standard manner. Researchers were able to isolate the expectations consumers had based on a product’s visual appearance from their overall product perception using these different settings.
Expectations did not have the same effect on hedonic and sensory qualities, according to the study. Although the presence of crema raised quality expectations (a hedonic indication), the quantity of crema had no effect on the predicted quality (Fig. 1.1). The researchers also discovered that while they could see and taste the product normally, the perceived quality was higher than when they were blind in the mouth. This suggests that visual cues influenced the in-mouth experience in a beneficial way.
When we look at the research more closely, we can observe that smoothness (a sensory indicator) was highly linked to crema quantity, because coffees with crema were predicted to be smoother (visual condition) than coffees without crema (Fig. 1.2). In fact, as the amount of crema increased, so did the perceived smoothness in the mouth, which was most likely attributable to the physical texture features of crema. Overall smoothness was evaluated higher when customers could see and taste it rather than when they were blind in the mouth.
Crema is a key part of the espresso coffee experience, according to the study. In fact, the lack of crema reduced perceived quality and sensory qualities by lowering expectations for quality, overall taste, bitterness, and smoothness.
The Effect of Crema on Aroma Production
The perception of volatiles through the olfactory system is referred to as aroma (see also Chapter 18). There are two mechanisms for volatile organic molecules to reach the olfactory epithelium in the upper section of the nose. When odor-active substances enter through the nose, this is known as orthonasal stimulation. When people smell coffee, the scent molecules go along this path. Retronasal stimulation happens when odor-active components enter through the internal nares, which are located within the mouth, after tasting the coffee. The mechanism that influences orthonasal fragrance perception will be discussed in the following section.
The Nespresso system was employed in one study to look at the effect of crema thickness and stability on scent release over the cup. They compared crema amounts (Barron et al., 2012) and stabilities (Dold et al., 2011) to coffee without crema. Despite the fact that it has long been assumed that crema functions as a lid to keep odors from escaping (Petracco, 2005), the experiments revealed a far more sophisticated mechanism.
The investigation traced fragrance molecules with varied volatilities above the cup as a function of time using MS methods. The existence of crema generally caused an above-the-cup volatile concentration that was much higher than that reported in liquid coffee without crema within the first 2.5 minutes after the start of extraction (Figs. 1.3 and 1.4).
In fact, when the narrow lamella at the foam surface ruptures, the bubbles collapse, and entrapped gas, primarily high volatile aromas, is released. The main source of this bubble rupture is thought to be the thinning of the films due to evaporation (Dold et al., 2011; Weaire and Hutzler, 1999), but other events outlined in Section 2 may also play a role. Furthermore, as the liquid evaporates, the low-volatile smells in the liquid also evaporate into the air. When there is no crema present, however, all fragrance release (including high and low volatiles) is solely driven by evaporation from the liquid to the gas phase.
Crema stabilization begins to have a vital influence on the release pattern after the initial release of aromas. The coffee releases the greatest amount of smells into the headspace when the crema stability is low. At the same time, crema volume is inversely associated to the release of low volatiles, which is most likely due to the crema acting as a “cover” that keeps odors from escaping.
Parenti et al. (2014), who investigated different espresso preparations, verified the idea that the crema layer works as a way to liberate fragrances above the cup when the crema layer is unstable. When the fragrance quantity was assessed above the cup, this study found an inverse link between crema quantity and stability.
Finally, when considering the effect of crema on scent release, we must examine a variety of methods. This should include: (1) how low crema stability (high bubble rupture) enhances the release of high volatile aromas, which are abundant in the gas phase of foam bubbles; (2) how high crema stability retains high volatiles because the crema acts as a barrier that entraps the aromas; and (3) how crema collapse allows for diffusion and the subsequent release of low-volatile aromas.
For all of these reasons, while creating new espresso brewing methods, crema and aroma releases are frequently prioritized. The Caffe’ Firenze, for example, uses pressurized air to generate espresso coffee with a longer-lasting froth layer (Masella et al., 2015). The decreased volatility of scent molecules above the cup is attributed to this foam layer. As a result, prior studies indicating that crema stability has a significant impact in scent release are confirmed (Dold et al., 2011).
Crema production has also been employed to improve the sensory elements of soluble coffee by researchers. For example, with soluble coffees with pressurized internal gas, one study focused on scent release above the cup for producing crema (Yu et al., 2012). This research, however, cannot be related to the previously established mechanisms of fragrance emission. This is due to the fact that the coffee preparation method is based on gas integration in the soluble extract rather than extraction technology.
Centrifusion, a newer method used by Nespresso in its VertuoLine system, relies on spinning for extraction rather than pressure to drive water through the coffee bed. The system produces crema in this case by combining gas expansion and mechanical formation.
The investigations mentioned above are all based on analytical methodologies that were used to measure or uncover the mechanism of the cup fragrance release indicated above. There are currently no sensory or consumer data that demonstrate the effect of crema on the perceived above-cup scent, to our knowledge. Various research, on the other hand, has looked at sensory perception in the mouth.
Crema’s Effect on In-Mouth Perception
There is research on how coffee tastes in the mouth (Charles et al., 2015; Barron et al., 2012; Labbe et al., 2016) Only Barron and Labbe have focused on cremation to our knowledge. Researchers frequently employ a technique known as temporal dominance of sensation (TDS).
Pineau et al., 2009; Le Re’ve’rend et al., 2008; Pineau et al., 2012; Pineau and Schlich, 2015) used this methodology to track the temporal evolution of sensory perception during product tasting.
Barron et al. (2012) focused on the consumption of a dark roasted powerful espresso with a different amount of crema. The TDS was conducted on seven sips, allowing the entire cup to be consumed. The panelists had to select the dominating in-mouth perceptual feature from a list of 11 options for each sip: carbon, roasted, cereal, fruity, sweet, bitter, acidic, liquid, thick, gritty, and smooth.
The roasted dominance grows with increased crema quantity and remains dominant throughout the cup’s consumption, as seen in Fig. 1.5. A low crema quantity, or no crema, on the other hand, resulted in carbon dominance and bitterness.
The same study used nose-space analysis to validate these findings, which is a method for investigating scent release in vivo using mass spectrometry to evaluate exhaled air during intake (Barron et al., 2012).
The study found that a larger crema quantity resulted in higher overall intensity. By combining the TDS and nose-space data, we may deduce that smells trapped in the crema can be detected by sensory perception and recorded in the nose space during consumption.
However, because variances across panelists can be significant, obtaining results using nose-space analysis can be difficult. With developments in analytical methodologies for nasal space analysis, researchers may be able to acquire better results in the future. By combining time of flight to MS, some investigations have indicated analytical improvement in increasing sample discrimination (Romano et al., 2014).
Outlook
Crema is much more than meets the eye. While the belief that a good crema must be dark brown and a certain thickness is not erroneous, it does not fully use the crema’s potential in the coffee experience. Although the taste of espresso coffee is the most significant component in customer choice, consumers also value the texture and mouthfeel of the beverage.
There’s a lot more to crema than meets the eye. Although the assumption that a good crema must be dark brown and of a specific thickness is not incorrect, it does not fully leverage the potential of crema in the coffee experience. Although the flavor of espresso coffee is the most important factor in consumer preference, the texture and mouthfeel aspects are also important.
Mouthfeel qualities can be divided into components relating to viscosity (thick), substances (rich), resistance to the tongue (round), after-sensation (lingering), coating of the oral cavity (mouth-coating), and feeling on soft tissue, according to Navarini et al. (2004b) (smooth).
Varying coffee procedures are said to produce different concentrations, and a mouthfeel vocabulary should be used to characterize these various beverages. Crema has been demonstrated to increase the olfactory qualities of the coffee, as well as build anticipation for the consumption of espresso coffee, in addition to its aesthetic appearance and texturization.
Despite the extensive understanding of coffee composition and foam production in beer, milk froth, and effervescent beverages, little is known about coffee crema formation and durability. The results so far have mostly been descriptive, with little proof of the systems’ proportional importance in espresso coffee. There is some understanding of the components that play a vital role in the creation and stability of crema.
Foams, on the other hand, are well-known for being extremely difficult to analyze due to their dynamics and many phenomena happening on the foam at the same time. As a result, the majority of study on this topic is focused on model systems, which employ one or two components to provide a more systematic approach to understanding creation and stability. Many diverse compounds are present in real food systems, resulting in a huge rise in complexity.
Espresso is, without a doubt, a complicated polyphasic liquid made up of (1) an emulsion of oil droplets, (2) a suspension of solid particles, and (3) the effervescence of gas bubbles that eventually form a foam (Illy and Viani, 2005).
To better comprehend espresso crema at varied lengths and time scales, a multidisciplinary approach using the most modern and extremely advanced analytical tools is required. This necessitates more thorough and focused research into coffee foam and the factors that influence its creation and stability. Only when the chemical compounds and their production and destabilization mechanisms are properly known can they be used as triggers to change the crema.
Developing ways to improve espresso crema, which may involve blending, roasting, grinding, tempering, and extraction characteristics such as water quality, requires combining the consumer impression of crema with a molecular and physical approach. This unique technique necessitates taking into account the espresso coffee in its whole.
According to Navarini et al. (2004b), mouthfeel attributes may be classified into components pertaining to viscosity (thick), substance content (rich), tongue resistance (round), after-sensation (lingering), oral cavity coating (mouth-coating), and soft tissue feeling (smooth).
Different coffee processes yield varying concentrations, and a mouthfeel vocabulary should be employed to describe these diverse drinks. Crema has been shown to enhance the coffee’s aromatic properties and to create anticipation for its intake, in addition to its visual look and texturization.
Despite significant knowledge of coffee composition and foam generation in beer, milk froth, and effervescent drinks, little is known about the development and endurance of coffee crema. Thus far, the findings have been primarily descriptive, with little evidence for the systems’ relative role in espresso coffee.
There is a basic awareness of the components necessary for the formation and stability of crema. On the other hand, foams are well-known for being incredibly difficult to examine owing to their dynamics and the multitude of events occurring simultaneously on the foam. As a consequence, the bulk of research on this subject is concentrated on model systems, which involve just one or two components and so give a more methodical approach to studying formation and stability. Numerous different chemicals exist in natural food systems, resulting in a significant increase in complexity.
Espresso is unquestionably a complex polyphasic liquid composed of (1) an emulsion of oil droplets, (2) a suspension of solid particles, and (3) the effervescence of gas bubbles that finally create a foam (Illy and Viani, 2005).
To get a deeper understanding of espresso crema throughout a range of durations and time periods, a multidisciplinary approach using the most sophisticated analytical techniques is necessary. This demands further in-depth and targeted study on coffee foam and the elements affecting its formation and stability. Only until the chemical components, as well as their synthesis and destabilization processes, are fully understood can they be employed as triggers to alter the cremation.
To develop methods for improving espresso crema, which may include blending, roasting, grinding, tempering, and extraction qualities like as water quality, it is necessary to combine the consumer perception of crema with a molecular and physical approach. This one-of-a-kind approach demands considering the espresso coffee in its whole.
