Hierarchical Multi-Task Learning for Healthy Drink Classification

Recent advances in deep convolutional neural networks have enabled convenient diet tracking exploiting photos captured with smartphone cameras. However, most of the current diet tracking apps focus on recognizing solid foods while omitting drinks despite their negative impacts on our health when consumed without moderation. After an extensive analysis of drink images, we found that such an absence is due to the following challenges that conventional convolutional neural networks trained under the single-task learning framework cannot easily handle. First, drinks are amorphous. Second, visual cues of the drinks are often occluded and distorted by their container properties. Third, ingredients are inconspicuous because they often blend into the drink. In this work, we present a healthy drink classifier trained under a hierarchical multi-task learning framework composed of a shared residual network with hierarchically shared convolutional layers between similar tasks and task-specific fully-connected layers. The proposed structure includes two main tasks, namely sugar level classification and alcoholic drink recognition, and six auxiliary tasks, such as classification and recognition of drink name, drink type, branding logo, container transparency, container shape, and container material. We also curated a drink dataset, Drinkl01, composed of 101 different drinks including 11,445 images overall. Our experimental results demonstrate improved classification precision compared to single-task learning and baseline multi-task learning approaches.