Netizens have questioned the safety of the box lunches with extra-long guarantee periods supplied on high-speed trains, though scientific test have proved the food is safe to eat. A passenger, surnamed Su, from Hefei of Anhui province, purchased a box lunch on a bullet train from Shanghai to Hangzhou on Oct 3 and noticed it had a guarantee period of six months. He posted pictures online and said: \"On railways in other countries, the meal produced in the morning will be thrown away at noon for the sake of food safety.\" An investigation carried out by Shanghai Morning Post last week found two such box lunches produced a month ago. One of the lunches had a guarantee of 90 days and the other six months. Sold at around 30 yuan ($4.7) each, the box lunches contained rice, beef, potatoes, eggs and carrots, and the labels stated that no additives had been used. The paper sent the two samples to a laboratory in Shanghai for testing. The results of the tests showed that the food had not deteriorated and there were no illegal additives. A spokesperson with the Shanghai Railway Bureau, who insisted on anonymity, explained that they offered such box lunches with long guarantee periods only on long-distance trains. \"Some trains leave today and return (to Shanghai) the next day. We are afraid the safety of food purchased in places outside Shanghai (for the return trip) is unsafe,\" the spokesperson said, adding fresh box lunches are supplied on short-distance trains. Two companies provide the box lunches to bullet trains departing from Shanghai. Shen Shixiu, a manager with one of the two companies, told Shanghai Morning Post that they had production licenses from the authorities and had been producing box lunches for six years. Nevertheless, both companies refused to explain the technologies used to preserve the food and declined requests to visit their production lines. Zhang Yu, who tried one of the box lunches a few weeks ago, said she will not buy another bullet train lunch box, not because of safety concerns, but because she thinks they are not worth the money. \"I\'m not worried about the quality,\" she said. \"But for 30 yuan, we deserve something better.\" Dong Jinshi, executive vice-president of the International Food Packaging Association, a Hong Kong-based non-government organization, told China Daily on Sunday that with the current technology it is possible to guarantee a six-month-long period for food storage. \"Preserving these types of box lunches is like canned food, and canned food can normally be preserved for more than a year,\" he said. But Dong said food manufacturers have a responsibility to provide consumers with an explanation of how they prevent the food from deteriorating. \"If they cannot issue evidence to clear themselves, there will be suspicions of trickery or fraud,\" he said.