Visual Inspection of Cafeteria Waste by Quarter Servings Rivals the Accuracy of Weighing

Abstract

ObjectiveWeighing plate waste is the gold standard measure of determining what is eaten in school cafeterias, but it is costly and time consuming. Four common methods of analyzing tray waste – percentage estimates, quarter serving estimates, top-down photographs, and angled photographs – are compared to determine their accuracy.Theory, Prior Research, RationaleNo prior research has compared all of the leading plate waste estimation methods to determine which is most accurate and efficient to use in large scale operations.Study Design, Setting, Participants, and InterventionTray waste from 233 K-12 lunchroom trays in Lansing, New York were measured in each of 5 different ways: weighing, percentage estimates, quarter serving estimates, top-down photographs, and angled photographs.Outcome, Measures and AnalysisEstimation accuracy compared with weighing.ResultsBoth methods of photography tended to underestimate the amount of wasted food by approximately 12%. Percentage estimation showed a bias of 6% but had the lowest retest reliability. Quarter serving estimation (0, 25, 50, 75, or 100%) most accurately approximated actual weight (-3.2%). This is largely because most items are either in total, uneaten or only have 1to 2 bites (25%) out of them.Conclusions and ImplicationsThe new USDA focus on reducing plate waste will make plate waste analysis important on a large-scale basis. This research suggests that using the quarter serving estimate method can be used quickly, widely, and inexpensively to approximate how much has been eaten when weighing is not possible.FundingNone. ObjectiveWeighing plate waste is the gold standard measure of determining what is eaten in school cafeterias, but it is costly and time consuming. Four common methods of analyzing tray waste – percentage estimates, quarter serving estimates, top-down photographs, and angled photographs – are compared to determine their accuracy. Weighing plate waste is the gold standard measure of determining what is eaten in school cafeterias, but it is costly and time consuming. Four common methods of analyzing tray waste – percentage estimates, quarter serving estimates, top-down photographs, and angled photographs – are compared to determine their accuracy. Theory, Prior Research, RationaleNo prior research has compared all of the leading plate waste estimation methods to determine which is most accurate and efficient to use in large scale operations. No prior research has compared all of the leading plate waste estimation methods to determine which is most accurate and efficient to use in large scale operations. Study Design, Setting, Participants, and InterventionTray waste from 233 K-12 lunchroom trays in Lansing, New York were measured in each of 5 different ways: weighing, percentage estimates, quarter serving estimates, top-down photographs, and angled photographs. Tray waste from 233 K-12 lunchroom trays in Lansing, New York were measured in each of 5 different ways: weighing, percentage estimates, quarter serving estimates, top-down photographs, and angled photographs. Outcome, Measures and AnalysisEstimation accuracy compared with weighing. Estimation accuracy compared with weighing. ResultsBoth methods of photography tended to underestimate the amount of wasted food by approximately 12%. Percentage estimation showed a bias of 6% but had the lowest retest reliability. Quarter serving estimation (0, 25, 50, 75, or 100%) most accurately approximated actual weight (-3.2%). This is largely because most items are either in total, uneaten or only have 1to 2 bites (25%) out of them. Both methods of photography tended to underestimate the amount of wasted food by approximately 12%. Percentage estimation showed a bias of 6% but had the lowest retest reliability. Quarter serving estimation (0, 25, 50, 75, or 100%) most accurately approximated actual weight (-3.2%). This is largely because most items are either in total, uneaten or only have 1to 2 bites (25%) out of them. Conclusions and ImplicationsThe new USDA focus on reducing plate waste will make plate waste analysis important on a large-scale basis. This research suggests that using the quarter serving estimate method can be used quickly, widely, and inexpensively to approximate how much has been eaten when weighing is not possible. The new USDA focus on reducing plate waste will make plate waste analysis important on a large-scale basis. This research suggests that using the quarter serving estimate method can be used quickly, widely, and inexpensively to approximate how much has been eaten when weighing is not possible.