Characterization particulate matter from several Chinese cooking dishes and implications in health effects.

Cooking fume produced by oil and food at a high temperature releases large amount of fine particulate matter (PM) which have a potential hazard to human health. This chamber study investigated particle emission characteristics originated from using four types of oil (soybean oil, olive oil, peanut oil and lard) and different kinds of food materials (meat and vegetable). The corresponding emission factors (EFs) of number, mass, surface area and volume for particles were discussed. Temporal variation of size-fractionated particle concentration showed that olive oil produced the highest number PM concentration for the entire cooking process. Multiple path particle dosimetry (MPPD) model was performed to predict deposition in the human respiratory tract. Results showed that the pulmonary airway deposition fraction was the largest. It was also found that particles produced from olive oil led to the highest deposition. We strongly recommend minimizing the moisture content of ingredients before cooking and giving priority to the use of peanut oil instead of olive oil to reduce human exposure to PM.

Changes in food quality and characterization under thermal accumulation conditions during Chinese cooking.

Chinese cooking is the primary treatment method for table food in China. The process is complex and large-scale, which is important to the macroeconomy and national nutrition and health. First, this article puts forward the concept of thermal accumulation for Chinese cooking by taking pork tenderloin fried at different oil temperatures, explaining changes in moisture content, hardness, and color with different thermal accumulation conditions, and measuring kinetic parameters. The variations of L* and b* obtained by the experimental results belong to the first-order reaction kinetic model, while the changes in water content and shear force belong to the zero-order reaction kinetic model. Simultaneously, the superheat value is used as a thermal accumulation indicator, combined with sensory evaluation to determine that the Z value of the human sensory overheating of pork tenderloin is 99°C, and O s,max (Z = 99°C, the reference temperature is 110°C) is 5.86 min.

Emission and capture characteristics of Chinese cooking-related fine particles.

Cooking can emit high concentrations of particles and gaseous pollutants. Cooking has contributed to the major source of indoor air pollutants, especially for particle pollutants in residential buildings. Many studies already analyzed the emission characteristics of Chinese cooking-related UFPs and PM2.5, while less for the fine particle size distributions. Currently, the fine particle emission characteristics of Chinese cooking need to be further investigated, since the mass size distribution of Chinese cooking is dominated by fine particles. This study determined the emission characteristics of PM1 and fine particles from three Chinese cooking methods. The capture efficiencies of particles were also measured by a modified indirect approach, including the impact of particle decay. The results showed that stir-fried vegetable and pan-fried meat dishes generated more fine particles at 0.542-1.5 µm. Besides, pan-fried and deep-fried meat dishes produce a higher generation of PM1. The fine particles (0.542-10 µm) number-based and volume-based size distributions of six dishes both presented a monodisperse behavior. The cooking methods are not a sensitive factor to the volume frequency of fine particle ranging from 0.542 to 10 µm. The averaged volume median and mode diameter for six typical Chinese dishes are 2.5 µm and 3.3 µm, respectively. The Sauter and DeBroukere mean diameter is 4.7 µm and 5.6 µm, respectively. The decay of fine particles increases with the particle diameter. The impact of particle decay on capture efficiency for 2-3 µm particles is about 5%. The capture efficiencies of pan-fried and deep-fried meat dishes are lower than that of vegetable dishes. In contrast, the capture efficiency for stir-fried meat dishes is higher than that of vegetable dishes. The capture efficiency for PM1 and 0.542-5 µm particles from six typical Chinese dishes were 60-90% on the IEC recommended exhaust flowrate.

Indoor sources strongly contribute to exposure of Chinese urban residents to PM2.5 and NO2.

Ambient fine particulate matter (diameters <2.5 µm; PM2.5) and nitrogen dioxide (NO2) pollution are responsible for substantial health burdens in China, contributing to a considerable proportion of global mortality. Simultaneously, the proportion of indoor smoking and cooking-induced PM2.5 and NO2 pollution lacks robust exposure assessment findings. Rapid poverty alleviation and urbanization affect the proportion of indoor vs outdoor sources of PM2.5 and NO2 exposures in China. The current understanding of air pollution and health lacks an understanding of source-specific air pollution exposure. Thus, we developed a model to estimate human exposure to pollutants originating indoors and outdoors. We found indoor sources strongly contribute to total PM2.5 and NO2 exposure in urban China and are comparable to outdoor sources. Cooking contributes 28.6 µg m-3 PM2.5 and 10.8 µg m-3 NO2 on average to the air people breathe, and so did smoking contributing 14.2 µg m-3 PM2.5 and 0.6 µg m-3 NO2, respectively. The results give us a clearer understanding of exposure to PM2.5 and NO2 from indoor and outdoor sources. Pollutant control policies on ambient exposure levels without addressing indoor air pollution in China are insufficient given our estimated exposure levels.

Vertically-resolved indoor measurements of air pollution during Chinese cooking.

Chinese cooking features several unique processes, e.g., stir-frying and pan-frying, which represent important sources of household air pollution. However, factors affecting household air pollution and the vertical variations of indoor pollutants during Chinese cooking are less clear. Here, using low-cost sensors with high time resolutions, we measured concentrations of five gas species and particulate matter (PM) in three different sizes at multiple heights in a kitchen during eighteen different Chinese cooking events. We found indoor gas species were elevated by 21%-106% during cooking, compared to the background, and PMs were elevated by 44%-159%. Vertically, the pollutants concentrations were highly variable during cooking periods. Gas species generally showed a monotonic increase with height, while PMs changed more diversely depending on the cooking activity's intensity. Intense cooking, e.g., stir-frying, pan-frying, or cooking on high heat, tended to shoot PMs to the upper layers, while moderate ones left PMs within the breathing zone. Individuals with different heights would be subject to different levels of household air pollution exposure during cooking. The high vertical variability challenges the current indoor standard that presumes a uniform pollution level within the breathing zone and thus has important implications for public health and policy making.

Comparison of PM2.5 emission rates and source profiles for traditional Chinese cooking styles.

The number of restaurants is increasing rapidly in recent years, especially in urban cities with dense populations. Particulate matter emitted from commercial and residential cooking is a significant contributor to both indoor and outdoor aerosols. The PM2.5 emission rates and source profiles are impacted by many factors (cooking method, food type, oil type, fuel type, additives, cooking styles, cooking temperature, source surface area, pan, and ventilation) discussed in previous studies. To determine which cooking activities are most influential on PM2.5 emissions and work towards cleaner cooking, an experiment design based on multi-factor and level orthogonal tests was conducted in a laboratory that is specifically designed to resemble a professional restaurant kitchen. In this cooking test, four main parameters (the proportion of meat in ingredients, flavor, cooking technique, oil type) were chosen and five levels for each parameter were selected to build up 25 experimental dishes. Concentrations of PM2.5 emission rates, organic carbon/elemental carbon (OC/EC), water-soluble ions, elements, and main organic species (PAHs, n-alkanes, alkanoic acids, fatty acids, dicarboxylic acids, polysaccharides, and sterols) were investigated across 25 cooking tests. The statistical significance of the data was analyzed by analysis of variance (ANOVA) with ranges calculated to determine the influence orders of the 4 parameters. The PM2.5 emission rates of 25 experimental dishes ranged from 0.1 to 9.2 g/kg of ingredients. OC, EC, water-soluble ions (WSI), and elements accounted for 10.49-94.85%, 0-1.74%, 10.09-40.03%, and 0.04-3.93% of the total PM2.5, respectively. Fatty acids, dicarboxylic acids, n-alkanes, alkanoic acids, and sterols were the most abundant organic species and accounted for 2.32-93.04%, 0.84-60.36%, 0-45.05%, and 0-25.42% of total PM2.5, respectively. There was no significant difference between the 4 parameters on PM2.5 emission rates, while a significant difference was found in WSI, elements, n-alkanes, and dicarboxylic acids according to ANOVA. Cooking technique was found to be the most influential factor for PM2.5 source profiles, followed by the proportion of meat in ingredients and oil type which resulted in significant difference of 183.19, 185.14, and 115.08 g/kg of total PM2.5 for dicarboxylic acids, n-alkanes, and WSI, respectively. Strong correlations were found among PM2.5 and OC (r = 0.854), OC and sterols (r = 0.919), PAHs and n-alkanes (r = 0.850), alkanoic acids and fatty acids (r = 0.877), and many other species of PM2.5.

Role of Chinese cooking emissions on ambient air quality and human health.

Chinese-style cooking often involves volatilization of oils which can potentially produce a large number of pollutants, which have adverse impact on environment and human health. Therefore, we have reviewed 75 published studies associated with research topic among Mainland China, Hong Kong and Taiwan, involving studies on the roles of food ingredients and oil type, cooking style impacting on generated pollutants, and human health. The highest concentration occurred including: 1) when peat, wood, and raw coal were used in stoves; 2) olive oil was adopted; 3) cooking with high temperatures; and 4) without cleaning technology. We conclude that PM concentrations for cooking emissions were between 0.14 and 24.46mg/cm3. VOC concentrations varied from 0.35 to 3.41mg/m3. Barbeque produced the greatest mass concentrations compared to Sichuan cuisine, canteen and other restaurants. The PAHs concentration emitted from the exhaust stacks, dining area and kitchen ranged from 0.0175µg/m3 to 83µg/m3. The largest amount of gaseous pollutants emitted was recorded during incomplete combustion of fuel or when a low combustion efficiency (CO2/ (CO+CO2)<0.5) was observed. The variation range was 6.27-228.89mg/m3, 0.16-0.80mg/m3, 0.69-4.33mg/m3, 0.70-21.70mg/m3 for CO, CO2, NO2 and SO2 respectively. In regards to the toxicity and exposure, current findings concluded that both the dose and exposure time are significant factors to be considered. Scientific research in this area has been mainly driven by comparison among emissions from various ingredients and cooking techniques. There is still a need for more comprehensive studies to fully characterise the cooking emissions including their physical and chemical transformations which is crucial for accurate estimation of their impacts on the environment and human health.