Astringency and its sub-qualities: a review of astringency mechanisms and methods for measuring saliva lubrication.

Astringency is an important mouthfeel attribute that influences the sensory experiences of many food and beverage products. While salivary lubricity loss and increased oral friction were previously believed to be the only astringency mechanisms, recent research has demonstrated that nontactile oral receptors can trigger astringency by responding to astringents without mechanical stimulation. Various human factors have also been identified that affect individual responses to astringents. This article presents a critical review of the key research milestones contributing to the current understanding of astringency mechanisms and the instrumental approaches used to quantify perceived astringency intensity. Although various chemical assays or physical measures mimic in-mouth processes involved in astringent mouthfeel, this review highlights how one chemical or physical approach can only provide a single measure of astringency determined by a specific mechanism. Subsequently, using a single measurement to predict astringency perception is overly idealistic. Astringency has not been quantified beyond the loss of saliva lubrication; therefore, nontactile receptor-based responses must also be explored. An important question remains about whether astringency is a single perception or involves distinct sub-qualities such as pucker, drying, and roughness. Although these sub-quality lexicons have been frequently cited, most studies currently view astringency as a single perception rather than dividing it into sub-qualities and investigating the potentially independent mechanisms of each. Addressing these knowledge gaps should be an important priority for future research.

Sensory properties of Australian bunya nuts.

Bunya nuts are the seeds of Araucaria bidwillii, a conifer native to South-East Queensland, Australia. They are one of the 19 species of Araucaria family found around the world, with the nuts from South America being the most commonly consumed. They are traditionally eaten boiled or roasted. This study aims to profile the sensory properties of bunya nuts with chestnut as a comparator. Since chestnuts do not come from a conifer tree, it is expected that there will be differences. Different methods of preparation are also expected to change the sensory attributes. Representative samples were collected from a variety of locations in South-East Queensland, prepared and presented to a panel of 14 experienced tasters applying conventional sensory descriptive profiling. During training, the panel developed a lexicon of 23 sensory attributes together with definitions and reference. Profiles of the boiled and roasted bunya nuts revealed higher scores for hardness on the first bite than chestnuts and, when chewed, became more crumbly, dry, and grainy. They had a savory aroma and flavor, and roasted samples exhibited a roasted aroma. Bunya nut samples were less sweet than chestnut samples. Differences in the sensory properties due to method of preparation were also observed. Boiled bunya nuts were softer and moister, with lower scores for crumbly and grainy. This research is foundational in providing technical information on the sensory profile of this important Indigenous Australian nut and provides a strong basis to support novel food sector opportunities for the bunya nut as a reemerging food source not only in Australia, but also South America. PRACTICAL APPLICATION: There is an increase demand for local, sustainable, and natural foods. Bunya nuts are native to Australia and are part of the Araucaria family, which includes 19 species that can be found around the world. To the best of our knowledge there is no study characterizing Araucaria nuts in terms of sensory attributes. This study builds a lexicon for bunya nuts and compares to chestnuts. It also shows how different preparation methods affect its sensory attributes, as well as possible future uses in product development. The outcomes might provide information to support studies on Araucaria nuts in other countries.

Ring Shear Tester as an in-vitro testing tool to study oral processing of comminuted potato chips.

Oral processing of solid foods is an extremely dynamic and complicated activity that involves multiple processes in tandem such as comminution, mixing, dilution, hydration and enzymatic breakdown that gradually transform the food from a morsel or a bite to a bolus that is ready for swallowing. It is hypothesised that just after "first bite" and initial particle reduction and hydration of solid brittle foods, the response to deformation of food particles is analogous to studies on the flowability and cohesion of wetted powders, which are effectively characterised using a Ring Shear Tester (RST). We examine this hypothesis and determine whether the RST measures properties of solid snack foods (potato chips or crisps, PCs) that are relevant to their dynamic sensory response, which includes capturing the effect of hydration on comminuted PCs. The RST is found to differentiate PCs obtained from different manufacturing sources (e.g. baked versus fried), and its measurements of cohesion and friction can be considered in context of the structure and composition of the PCs as well as oral processing. Remarkably, RST measurements for this small set of PC samples correlate with several sensory attributes that arise during mastication, which includes Sharpness and Ease of Clearance. This study highlights the potential of the RST as a new tool for oral processing research.