Gulp: Adventures on the Alimentary Canal

In the opening chapter of Gulp, Roach explores the fundamental role that smell plays in taste perception through her encounters with professional sensory analyst Sue Langstaff. Roach begins by describing how Langstaff enjoys riding motorcycles for an atypical reason: to experience the rich array of smells that flow into her nose during travel. This anecdote establishes the central premise that tasting is primarily about smelling rather than what happens on the tongue.

Roach explains the science behind this phenomenon: Humans can only detect five basic tastes (sweet, bitter, salty, sour, and umami), but they can perceive an almost infinite number of smells. Between 80-90% of what people experience as flavor comes from olfaction, not taste buds. The process involves two types of smelling: orthonasal (through external nostrils) and retronasal (through internal passages when food is in the mouth). Professional evaluators like Langstaff excel not because they have more sensitive noses, but because they can identify and separate individual components within complex flavor profiles.

To demonstrate the challenges of flavor identification, Roach accompanied Langstaff to a beer tasting where Langstaff effortlessly identified specific notes while Roach struggled to recognize any distinct elements. Roach uses this to illustrate a key point: Humans are naturally better equipped for visual processing than olfactory analysis. She cites a famous study where wine students described the same white wine differently when it was artificially colored red, showing how visual cues can override actual sensory information.

The chapter concludes with Roach’s attempt to join an olive oil tasting panel at UC Davis, where she failed spectacularly at identifying oils and ranking their bitterness levels. Her failure contrasted sharply with industry professionals who performed exceptionally well—although, interestingly, these experts sometimes missed common aromas outside their specialty area. Through these experiences, Roach concludes that sensory evaluation is a learned skill requiring extensive practice and exposure.

Roach explores the pet food industry by visiting AFB International, a company that creates flavor coatings for dry pet food. She observes their testing facility where dogs and cats evaluate different kibble formulations. The chapter reveals the fundamental challenge facing pet food manufacturers: balancing what animals need nutritionally with what human consumers want in terms of convenience and cost.

Roach explains how dry pet food became popular during World War II, when tin rationing ended canned dog food production. While owners appreciated the convenience of dry food, the resulting cereal-based pellets lacked appeal for pets. This created the need for palatants—flavor coatings that make nutritionally complete but bland kibble more appetizing to animals.

The author examines the science of animal taste perception through conversations with AFB researchers Pat Moeller and Nancy Rawson. She learned that cats are obligate carnivores who often prefer monotonous diets, while dogs rely more heavily on smell than taste when choosing food. Cats cannot taste sweetness due to evolutionary adaptation, whereas rodents can become addicted to sugar. The chapter includes Roach’s experiment tasting pyrophosphate, a key palatant ingredient that appeals strongly to cats but tastes strange to humans.

At AFB’s testing facility, Roach observes preference tests comparing different kibble formulations. She notes the careful methodology required to account for individual animal behaviors and the challenge of creating products that smell appealing to pets without offending human owners. The research reveals that while decomposing protein compounds excite dogs, the scents must remain tolerable to humans who purchase and serve the food.

The chapter concludes with a discussion of organ meat’s nutritional superiority. Roach presents evidence from a 1970s study showing that some dog foods ranked higher nutritionally than common human protein sources like steak and hamburger. She notes that organs, which form the primary ingredients in many palatants, contain concentrated vitamins and minerals that muscle meat lacks. This leads to her observation that Americans export vast quantities of organ meat to other countries while consuming nutritionally inferior processed foods themselves.