Jane K. Parker

Adding water to chocolate is known to cause a large increase in the concentration of Strecker aldehydes, which are key aroma compounds in cocoa. 3-Oxazolines may be precursors responsible for this; however, only a low concentration of 2-isobutyl-5-methyl-3-oxazoline was previously identified in chocolate. This study investigates the possibility that other types of 3-oxazolines are the relevant precursors present in cocoa. A range of novel 3-oxazolines were synthesized and characterized by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy. Using the synthesized compounds as references, four of these were identified by GC-MS for the first time in aroma extracts of cacao nibs, cocoa liquor, and chocolate, obtained by solvent-assisted flavor evaporation. This study may reveal a new focus for enhancing cocoa aroma and potentially other roasted food products as well.

Off-notes in plant-based sources of protein are mainly formed via the lipid oxidation of unsaturated fatty acids. During gas chromatography-olfactometry analysis of pea protein isolate, previously uncharacterized old soap odors were detected. These were found to arise from a family of α,β-unsaturated aldehydes formed from the aldol condensation of pentanal and hexanal during the protein extraction process. These compounds were synthesized, and it was confirmed that they are highly odor-active and contribute to the old soap odor in pea protein isolates at very low concentrations. Comparison with rice, soy, and hemp protein isolates showed that they all contained at least one such aldol condensate, whereas they were not detected in whey protein. We suggest that the main factor determining the formation of these compounds is the manufacturing process used to isolate and dry the pea protein biomass.

Spontaneous fermentation is currently used to produce lafun from cassava, leading to inconsistent product quality and decreased safety. Using starter cultures and optimising the selection of the raw materials can overcome this. This study evaluated the impact of various lactic acid bacteria (LAB) starters and varieties of cassava (bitter: IBA30527; vitamin A fortified bitter: IBA011371; and sweet: TMEB117) on the proximate, rheological, and volatile profiles of lafun. The varieties were fermented with four selected LAB (two strains of Weissella koreensis, Lactococcus lactis, and Leuconostoc mesenteroides). The use of fortified cassava showed higher potential to improve the quality of lafun. The combination of fortified cassava and Leuconostoc mesenteroides gave the highest nutritional value (ash: 4.37% cf. 1.33%; protein: 3.08% cf. 0.87%; and fibre: 7.43% cf. 1.43%). Fermenting the fortified cassava with Weissella koreensis-2 produced lafun gruel with the best viscoelastic properties, indicating an overall better product quality. The fortified cassava fermented with combined cultures of W. koreensis-1 and L. lactis resulted in a product with lower levels of carboxylic acids (cheesy) and lipid oxidation products (fried, rancid) but higher concentrations of carotenoid-derived compounds (fruity). The use of LAB in the controlled fermentation of fortified cassava could be a sustainable alternative to improve the physical, nutritional, and flavour properties of lafun.

The aim of this work was to identify volatiles that contribute to the aroma of cooked cheese, including the role of fat content in their development during cooking. Volatiles and odorants in cooked mature Cheddar were identified using a combination of SPME (solid‐phase microextraction)/GC–O (gas chromatography–olfactometry) and SPME/GC–MS (gas chromatography–mass spectrometry). A selection of the odorants was quantitated in six cheeses, uncooked and cooked, (mature Cheddar, high‐, medium‐, and low‐fat mild Cheddar, mozzarella, and Parmesan). Many compounds showed significant differences between cooked and uncooked cheese; Strecker aldehydes, pyrazines, and furanones were all significantly higher in cooked cheeses than in uncooked cheese, while ethyl esters (key odorants in uncooked cheese) were not detected in any of the cooked cheese. Principal component analysis demonstrated that fat concentration in mild Cheddar was positively correlated with the formation of potential odorants (the Strecker aldehydes, methanethiol, 2‐methylketones, and fatty acids) upon cooking. Potential lipid precursors for these compounds are discussed. Practical Application: This research can be used by the dairy industry to develop better cheeses, especially low‐ and reduced‐fat cheeses, for use in cooked applications such as toppings for pizzas and ready meals. Alternatively, this research describes key volatile compounds in cooked cheese that can be used by the flavoring industry to develop authentic cooked cheese flavorings.

This work examined the role of selected non-volatile compounds in cooked cheese flavour, both as tastants and as precursors of aroma generation in the Maillard reaction. The effect of cooking on the concentration of selected non-volatile compounds (organic acids, sugars, amino acids, γ-glutamyl dipeptides, and diketopiperazines) in six cheeses (mature Cheddar, mozzarella, Parmesan, and mild Cheddar (low, medium, and high fat)) was determined. Sugars, amino acids, and γ-glutamyl dipeptides were extracted and analysed by LC, whereas diketopiperazines were extracted by solid-phase extraction and analysed by GC-MS. Sugars, amino acids, and γ-glutamyl dipeptides decreased in concentration during cooking, whereas diketopiperazines and some organic acids increased in concentration. Diketopiperazines were above the taste threshold in some cooked cheeses and below the threshold in uncooked cheeses. The role of fat content in cooked cheese flavour is discussed. Furthermore, γ-glutamyl dipeptide concentration increased during 24 months of ageing in low, medium, and high-fat Cheddars, with similar levels of γ-glutamyl dipeptide detected in aged low and high-fat Cheddars. This work will give valuable insight for the dairy industry to inform the development of cheeses, especially low-fat variants, for use in cooked foods.

Mapping molecular structure to odor perception is a key challenge in olfaction. We used graph neural networks to generate a principal odor map (POM) that preserves perceptual relationships and enables odor quality prediction for previously uncharacterized odorants. The model was as reliable as a human in describing odor quality: On a prospective validation set of 400 out-of-sample odorants, the model-generated odor profile more closely matched the trained panel mean than did the median panelist. By applying simple, interpretable, theoretically rooted transformations, the POM outperformed chemoinformatic models on several other odor prediction tasks, indicating that the POM successfully encoded a generalized map of structure-odor relationships. This approach broadly enables odor prediction and paves the way toward digitizing odors.