An Instrumental and Sensory Characterization of V-Type Starch-Aroma Compound Inclusion Complexes
Restricted (Penn State Only)
- Author:
- Goza, Jennifer
- Graduate Program:
- Food Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 28, 2022
- Committee Members:
- Robert Roberts, Program Head/Chair
John Hayes, Major Field Member
Helene Hopfer, Chair & Dissertation Advisor
Travis Masterson, Outside Unit & Field Member
Ann-Marie Torregrossa, Special Member
Greg Ziegler, Major Field Member
Josephine Wee, Major Field Member - Keywords:
- starch-aroma inclusion complexes
starch
aroma compound
TCATA
flavor perception
salivary amylase activity
Headspace-GCMS
chewing gum
sensory science
aroma compound release
flavor encapsulation system - Abstract:
- Flavor is an integrated perception arising from taste, aroma, and chemical touch, important to food quality and consumer preference. Aroma compounds are volatiles released from the food matrix upon chewing and are perceived in the olfactory receptors in the nasal cavity. The stability of aroma compounds in food matrices is influenced by their chemical reactivity, the environment, and the macromolecular components of food matrices. For crops such as hops flowers whose primary commercial function is adding flavor and body to beer, their specific aroma compounds can be partially lost during postharvest processing techniques such as drying and lower the value of the final product. In food products, aroma compounds are often thermally unstable, migrate or diffuse out of the food due to their high volatility, and are often limited in their direct use in food applications due to their hydrophobicity. As a result, aroma molecule release from the food matrix and their interactions with the saliva and oral cavity environment prior to perception is not well understood. One way to overcome these limitations is encapsulation, where aroma compounds are entrapped in another material to limit or slow down the loss due to volatilization and/or to protect them from degradation. Complexation is a type of encapsulation where a larger “host” molecule provides a cavity or channel for a smaller “guest” compound to reside. Encapsulation systems based on starch inclusion complexes (ICs) are possible due to the structure of the amylose component of starch. Individual amylose helices cluster together to form “V-type” orthorhombic crystals. The linear glucose chains of amylose can be manipulated to form left-handed helices containing 6,7, or 8 glucose units per turn, known as V6, V7, or V8-type starch. Individual V-type starch helices feature a hydrophilic surface and a hydrophobic inner channel and are able to form inclusion complexes with a variety of compounds, including aroma compounds. The success of complexation depends on the molecular parameters of both guest and host, such as the size of the aroma compound and the diameter of the helices. The hydrophobicity of aroma compounds also impacts complexation. The efficacy of these V-type starches as encapsulation systems, studied in vitro using high temperatures, alkali treatments, and enzymatic hydrolysis with 𝛼-amylase, demonstrate that starch-aroma compound ICs show prolonged guest compound release compared to non-complexed guest molecules. However, it is unclear whether this prolonged in vitro release translates to prolonged flavor perception when used in a food application as flavor perception of such starch-aroma compound inclusion complexes has not been studied. Additionally, the impact of saliva composition on temporal flavor perception from these starch-aroma compound ICs is unknown, and the mechanisms driving aroma compound release is unclear. While the use of V-type starches as a protective material has been applied in different applications, such as a ripening modifier using ethylene gas release, its efficacy as a size-specific adsorbent trap for hydrophobic volatiles under dynamic headspace (HS) conditions has not been explored. The overall aim of this dissertation was to characterize the temporal aroma compound release behavior and flavor perception of starch-aroma compound ICs; and to explore the ability of V-type starches to adsorb hops volatiles under dynamic conditions. I hypothesized the following: V-type starch ICs in chewing gum will show prolonged flavor release; individuals will experience different flavor perception due to variations in saliva composition; different simulated saliva conditions will impact aroma compound release; and that empty V-type starch “helices” can adsorb hop aroma compounds. First, mint and citrus chewing gums with and without ICs were characterized for their sensory properties using Temporal Check-All-That-Apply (TCATA) and segmented Check-All-That-Apply (CATA). For the mint chewing gum study, fifty-six participants evaluated both a chewing gum containing starch-menthol IC and a control chewing gum containing free menthol. In the second study, one-hundred participants evaluated a sample and control citrus chewing gum in the same manner containing either starch-limonene ICs or free limonene. Participants evaluated the flavor perception of the attributes Minty, Cooling, Sweetness, Staleness, and Hardness for the mint chewing gums; and the attributes Citrus, Sour, Bitter, Sweet, Stale, and Cohesive for the citrus chewing gums. TCATA and CATA revealed differences in flavor perception resulting from differences in aroma delivery between the encapsulated and free flavor containing gums. This study demonstrated that TCATA was useful to study temporal perception of common aroma compounds in a chewing gum matrix. Further, a similarity between the TCATA curves for the primary sensory attributes for each study (i.e., Mint and Citrus) and instrumental aroma compound release curves, as measured by headspace concentration over time, was also observed. Second, the individual limonene chewing gum sensory results were further demarcated into three segments organized by participant salivary α-amylase activity (sAA) and salivary flow rate (sFR). Resulting Citrus, Sweet, and Bitter attribute curves of the chewing gum sample containing the inclusion complexes suggested that human flavor perception was impacted by participant salivary a-amylase activity (sAA) and salivary flow rate (sFR), highlighting the potential influence of these physiological factors on flavor perception of foods. The higher, sustained Citrus perception for individuals with high sAA and medium sFR may be explained by a higher rate of starch hydrolysis from high salivary a-amylase activity, and a lower saliva dilution effect due to a medium salivary flow rate. Compared to single attribute and dual-attribute time-intensity, TCATA is more suited to characterize flavor release systems as multiple flavor percepts can be simultaneously tracked which is beneficial especially when cross- and intra-modal perceptual interactions occur. Third, an instrumental approach was used to understand the impact of saliva composition on the temporal aroma compound release from the V-type starch ICs. Release of menthol, limonene, and menthone from V-type-aroma compound ICs was measured in the headspace above simulated saliva over a two-hour period. Different simulated saliva solutions were created by dissolving salivary proteins (a-amylase, mucin, combination of two proteins, none) in one of three buffer solutions of varying pH. Addition of salivary proteins (a-amylase and mucin) to the simulated saliva increased aroma compound headspace concentration, where the addition of mucin affected limonene HS concentrations more than the addition α-amylase, likely due to hydrophobic effects from mucin and a-amylase interactions. Menthone and menthol HS concentrations were more affected by the addition of a-amylase than mucin. The lower pH of the sodium acetate buffer possibly promoted mucin aggregation, which could have promoted higher limonene and menthol HS concentrations, but not menthone. Applying the Ritger-Peppas model to aroma compound release into the headspace from the starch-guest IC suspended in simulated saliva showed that the aroma compound and addition of salivary proteins had significant impact on the n coefficient. Complexation and hydrophobicity of the aroma compound impacts the flavor release curvature of the compound, as the most hydrophobic compound, limonene, is characterized by a steeper decay over time in contrast to menthol’s sustained headspace concentration. Last, the application of “empty” V-type starches as efficient absorbents of hops aroma compounds in a dynamic headspace sampling system was explored. I found that hydrophobic aroma compounds common in hops were adsorbed in the V6a-type starches only. The anhydrous V6a-type starch was able to trap detectable levels of myrcene, limonene, humulene, 𝛽-farnesene, pinene, and linalool, while V7-type, V8-type, and the waxy maize control did not trap hops volatiles. Hydrated V-type starch forms did not show any adsorption of hops volatiles. Repeated thermal desorption of V6a-type traps suggests that adsorbed hops volatiles are rather tightly associated with the starch, indicating a potential thermal stabilization of those labile compounds by the starch. Overall, using V-type starches as a flavor encapsulation system and as adsorbent traps both show potential. Further investigation is necessary to understand how and where complexation is occurring (e.g., inside the helices or between the helices) in order to optimize the preparation of the V-type starches and the approach to complexing more hydrophobic compounds. V-type starches could be also a useful tool to exploring how starch perception and digestion are linked.