Memory Influences Judgement of Food Quality

In what is believed to be a first, New Zealand scientists have demonstrated that humans can remember differences in the texture of food.

A team at public research institute, HortResearch, led by scientist Dr Roger Harker, has shown that humans’ ability to judge the quality of food relies of the memories of past eating experiences.

“To measure quality, it has to be something that’s in people’s minds. They have to be able judge differences across days. And therefore, there is quite a big component of memory involved in that,” says Dr Harker.

To test the hypothesis, the participants in the study — 14 members of the HortResearch staff who were not directly involved in fruit quality or fruit handling research — were asked to try and discern the differences in the texture of apples over one-day intervals and then one-minute intervals.

Over two weeks, the 14 staff were presented with 252 Royal Gala apples, each with a different level of firmness. Before each apple was given to the participants, the fruit had had its hardness assessed using a scientific instrument. Therefore, the scientists were able to relate the values from the instruments to the perceptions of the study participants.

In the daily tests, participants were able to detect the smallest difference in hardness, showing that they could rely on memory to discern a difference in texture. “Clearly there are some subtle differences in textures that can be detected by people, but not by current instrumental measurements,” the scientists write in the report in the journal Food Quality and Preference. “However, for large differences in texture, instrumental and sensory methods may be equally effective at discriminating between treatments.”

However, most participants had difficulty perceiving significant differences from the minute-interval tests. This difficulty in the shorter test also appears to support to the scientists’ argument, showing that the quick succession of apples caused difficulties with short-term memory, and that people need to rely on the ‘engram’ or constructed memory that they have of the texture of fruit.

The practical application of the study is that growers will now be able to consider whether consumers are likely to accept differences in texture that could result from a change in the way the apple is grown and stored.

“Such relationships are important for fruit scientists and industries forced to use instrumental measurements to evaluate and regulate for quality”” Dr Harker said in HortResearch’s newsletter Hothouse. “So, while machines and people may be equally effective at discriminating larger differences in texture, some more subtle differences can be detected only by people.”

And soon, apple eaters may be able to add flesh color to their memory bank. HortResearch’s latest newsletter also reports that in future, apples might come with flesh colors varying from red to pink to purple to gold and green. To develop these apples with different colored flesh, HortResearch scientist Dr Richard Volz and the pipfruit breeding team are mining the institute’s pipfruit germplasm collection.

“We first have to develop these new colors as separate breeding lines, only using the best selections to breed for new cultivars,” he told Hothouse. “To date we have over 13,000 seedlings in red, gold and green flesh breeding lines but we are most advanced with red flesh, with over 25 sources.”

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