The Expedition

Food for Thought: Protein Content Variation in Commercial Agaricus Bisporus Mushrooms

Hooria Bilal — 2024-09-04

Edible mushrooms have many nutritional benefits because they contain essential proteins and vitamins. However, various factors can influence their protein content including growth environment, packaging, and processing conditions. We collected nine samples of Agaricus bisporus mushroom species from three stores across metro Vancouver and conducted ninhydrin testing to compare their protein contents. Ninhydrin is a chemical compound that produces varying shades of violet when in contact with primary amino acids. We compared the shades of violet obtained from our mushroom samples to determine their protein amounts. Statistical testing revealed that the three differently sourced and stored mushrooms used in this experiment had no significant difference in protein concentration. This discovery was confirmed by a one-factor ANOVA test that produced a p-value of 0.3847. This result is unexpected as previous literature suggests that there should be a statistical difference in protein content between the mushrooms. Further research into the protein content of mushrooms should be conducted and the investigation of different factors like packaging and storage should be prioritized.

Are Nut Ingredients Accurately Labeled on Granola Bars?

Nataly El-Bittar — 2024-09-04

Individuals with allergies can have serious health complications after consuming foods with certain allergens. It can be difficult to ensure that packaged food will be allergen-free and can be safely consumed. Peanut and tree nut (Almond, Brazil Nut, Cashew, Hazelnut, Macadamia, Pecan, Pistachio, Walnut) allergies are some of the main food-induced reasons of anaphylaxis. We sought to determine whether we could detect all tree nut ingredients as labeled on granola bar packaging and predicted that all (100%) of the granola bars will be accurately labelled. We used 5 types of granola bars and isolated DNA from them. We conducted a polymerase chain reaction to detect 8 types of nuts in our samples. We ran the samples on a gel and analyzed the presence of tree nuts. We successfully detected nut products as labeled on the granola bar packaging in 4/5 (80%) of the samples. However, one granola bar sample labeled as “contains almonds” and almond powder (positive control) were not detected by the primer set leading to 1/5 (20%) false negative in the granola bar samples. Granola bars contain ingredients as listed on their packaging, suggesting that they can be trusted by consumers. Based on our findings, people should be cautious as there may be cross-contamination between tree nut allergens and peanut-free products.

Meat Mislabelling in Sausages: A Detailed Exploration Using DNA Analysis Techniques for Product Verification

Daniel He — 2024-09-04

Accurate food labelling is crucial for both food safety and consumer awareness, especially for sausages which are a major protein source for people worldwide. Our study examined a total of 6 different sausage samples: 2 beef, 2 pork, and 2 chicken. Meat primers used for the multiplex PCR procedure were cattle (beef), pig (pork), chicken, sheep, goat, and horse. We hypothesized that 1 out of 6 of the sausage samples would contain undeclared meat species based on the rates of sausage meat contamination in previous Canadian studies (Naaum et al., 2018; Shehata et al., 2019). Our results concluded that at least 16.67% of the 18 sausage samples contained undeclared meat species. Contamination was only found in pork sausage samples which additionally had horse, chicken and cattle DNA detected. While we expected to find a reduced rate of mislabelling compared to a decade ago, the detection of horse meat suggests that new sources of contamination may be emerging. Overall, these findings indicate that the prevalence of undeclared meat species in sausage products persists in the food industry given the health, cultural, and transparency issues involved.

Permeability of Free-Range and Caged Eggs in Different Solution Types

Chloe Law — 2024-09-04

In our research, we sought to assess the osmosis rate of free-range and caged eggs in water (control), salt solution, and sugar solution. For de-shelling, a dozen of free-range and caged eggs were soaked in vinegar for two days and washed with warm water. All the de-shelled eggs were then submerged in water before placing them in their respective treatment groups. Weight measurements were taken before and after treatments as indicators to assess the osmosis rate of eggs. We hypothesized that the greater presence of monounsaturated fatty acids in free-range eggs will result in higher membrane permeability in comparison to caged eggs. In our results, we found both free-range and caged eggs absorbed water and gained mass when submerged in water. We also discovered that both sugar and salt treatments withdrew water from the egg which resulted in decreased egg mass in free-range and caged eggs. We discussed the osmosis rate of free-range and caged egg membranes in response to the same concentration of hypertonic environment of various substances. Overall, our results showed a higher rate of osmosis in caged eggs compared to free-range eggs in different treatment environments. The membrane permeability variations can enhance our knowledge about the transport mechanism of the membrane and the nutritional properties of eggs. This understanding can offer significant perspectives on food safety and human health.

Comparative Analysis of Protein Content in Animal-based Chicken, Plant-based Chicken, and Tofu: An Experimental Study

Anson W. — 2024-09-04

This study aimed to compare and analyze the protein content in plant-based meat and animal-based meat. For this experiment, we selected three protein sources, including animal-based chicken nuggets, plant-based nuggets, and plant-based tofu, for the analysis. The research sought to determine whether plant-based meat alternatives would have similar or lower protein content than animal based chicken nuggets. In order to conduct the experiment, we first took three samples from each of our protein sources, and all samples were left in the dryer for 2 days to extract all the moisture. The samples were then ground into a fine powder, and water and ninhydrin were added before being placed in a water bath at 90 degrees Celsius for 20 minutes. The resulting colour change was recorded, and RGB values were extracted for the analysis. The study findings suggest no significant difference in protein content between the different samples.

What’s In Your Pet’s Food? A Study of Protein Contamination in Raw Pet Food Products

Bobby Athwal — 2024-09-04

Contamination of raw pet food products with unspecified animal DNA can jeopardize pet safety and waver the customer’s trust in its quality. While raw pet food diets are becoming more popular with pet owners, research and control over protein contamination is below par. Our team took 5 raw meat products (beef, chicken, kangaroo, pork, and sheep) from the local pet food manufacturer, hypothesized to be contaminated. The sample DNA was amplified and quantified using DNA isolation, PCR and gel electrophoresis, and gels were analyzed to determine contamination or lack thereof. We found that beef and chicken products were not contaminated with any of the tested primers’ DNA (beef, chicken, goat, horse, pork, sheep), but kangaroo, pork, and sheep samples showed contamination with bands that had a size predictive of beef DNA (274bp). The kangaroo meat contamination is suspected to be caused by a region of similarity between beef and kangaroo mitochondrial D-loop cytochrome B sequences, which could have led to a false positive. Further research should be done into kangaroo, sheep, and pork raw meat products to get a better understanding of the extent of protein contamination.

The Instance of Mussel Mislabeling Among Richmond and Vancouver Markets of Native M. trossulus, Invasive M.galloprovincialis and M.edulis, and their Hybrids

Alisha Dostie — 2024-09-04

Seafood fraud is a prevalent issue globally, and Canada is no exception with one of the highest rates of mislabelling in the world. This poses significant challenges to traceability, sustainability, and consumer protection. Among the commonly consumed types of mussels, the Blue Mussel (genus Mytilus) is particularly susceptible to mislabeling as a result of its morphological indistinguishability between multiple species, as well as its frequent hybridization. In this study, nine mussel samples, all believed to be M.galloprovincialis, were collected from three seafood markets in the Vancouver and Richmond area and were identified using PCR and gel electrophoresis. The banding patterns were compared to the expected banding patterns for each species of Mytilus to determine if the samples were labeled correctly or not. The results revealed that 11% of the mussel samples were mislabeled, or 1 out of the 9 mussels collected.

Effectiveness of Commercial and Homemade Cleaning Products on Preventing White Bread Microbial Growth

Eric Guo — 2024-09-04

Commercial cleaning agents are regularly used in disinfecting or general cleaning in many households. Two of the most common cleaning products, Lysol and Clorox, were tested against a homemade product made of a simple mixture of baking soda, dish soap, and white vinegar. Their effectiveness was studied by observing the amount of microbial growth on preservative-free white bread over a period of 12 days. The control group with only water showed the highest amount of mold growth. Besides the control, bread that was sprayed with Clorox product showed the most amount of mold growth, followed by Lysol. The homemade mixture was observed to have the lowest microbial growth out of all treatments. The p-value for ANOVA statistical analysis was p=0.1199. This research provides insight to consumers for better understanding of which products to purchase with the goal of best disinfecting results in mind.

Analysis of Tuna Species for Identification of Proper Labeling Practices in Tuna-Containing Products

Bhupesh Jassal — 2024-09-04

Numerous tuna-containing products were procured and tested via DNA isolation,
polymerase chain reaction, and gel electrophoresis respectively. This was done in order
to determine whether the labeled species of tuna is the species actually present in the
product. Included among these samples were raw tuna, canned tuna, and tuna from a
fast-food restaurant franchise for a total of five samples. These products were tested for
DNA pertaining to the following species of tuna: Bluefin, Yellowfin, Albacore, Bigeye,
and Skipjack. Our results yielded few conclusions as many of the products did not
produce legible banding patterns on agarose gels after electrophoresis. This was
probably due to metal contamination of the canned tuna samples. The fast-food tuna,
which also returned inconclusive banding patterns, was in turn tested for DNA
pertaining to livestock, including pig, cattle, goat, sheep, and chicken. All returned
inconclusive results. However, the two raw tuna samples were identified as Yellowfin
tuna and Ahi tuna (similar to Yellowfin and Bigeye tuna); both were labeled correctly.

A Comparison of the Fat Content Between Organic and Inorganic Processed Snack Food

Natalie Ma — 2024-09-04

Consumers look to organic food options as healthier alternatives to their favourite snacks. However, there is not much evidence that suggests that organic foods are in fact healthier than their inorganic counterparts, especially regarding the amount of fat in these foods. The objective of this study was to compare the fat content between organic and inorganic cookies and granola bars. This was investigated by using acetone-based solvent extraction to measure the fat content in Savor Organic Chocolate Vanilla Sandwich cookies, inorganic Oreo cookies, Annie’s Organic Dipped Chocolate Chip granola bars, and inorganic Quakers Dipps Chocolatey Chip granola bars. Based on the nutrition labels of these foods, we hypothesized that the organic varieties of the cookies and granola bars would have higher fat contents than the inorganic varieties. Yet, our study found no significant difference in the amount of fat between the organic Savor cookies and the inorganic Oreo cookies (p = 0.155), and the organic Annie’s granola bars and inorganic Quakers granola bars (p = 0.148). These results suggest that fat may not need to be a consideration for shoppers who look to buy organic foods as ‘healthier’ options.

Comparison of the Effectiveness of Lactaid Regular versus Lactaid Extra Strength versus Life Regular in Breaking down Lactose

Leah Campbell — 2024-09-04

This study aimed to determine the effectiveness of different lactase supplements in breaking down lactose. The hypothesis was that fast-acting lactase supplements would have a higher reaction rate than regular lactase supplements, assuming the same concentration of lactase. Three different lactase supplements were tested, including two from Lactaid® and one from Life, with the same lactase concentration of 18,000 food chemical codex (FCC). Glucose concentrations were measured over 20 minutes using a glucose meter to determine the rate of lactose breakdown. No observable differences were found between the measured glucose concentrations across all three lactase supplement brands, suggesting that the labels on lactase supplements can be misleading. This study provides insights into the efficacy of different lactase supplements, which can improve the quality of life for those with lactose intolerance.

The Effect of Glucose Concentration on Tetrahymena Thermophila Growth Rate

Gamen Gill — 2024-09-04

Tetrahymena Thermophila is a unicellular eukaryote with a doubling time of approximately 2 hours, making it ideal to study population growth. In the presence of nutrients, namely glucose, its growth rate can be further increased. The objective of our study was to determine how differing glucose concentrations would have an impact on the growth rate of T. Thermophila, using treatment concentrations of glucose at 0.2%, 1%, 3%, and 5%. We hypothesized that with increasing glucose concentration, growth rate would increase, with peak growth at 3% glucose. In this study, we placed T. Thermophila in media with varying glucose concentrations, and did trials at 3, 21, 24, and 27 hours, with cells kept incubated at 35℃ to promote optimal growth. Cell density was then determined using a haemocytometer. We found that the average population growth rate increased slightly from 0.2% glucose to 1%, before it significantly increased at 3% where it displayed the maximum growth rate, and then sharply declined at 5% glucose. Using a one-way ANOVA test, it was revealed that our results were not statistically significant (p=0.0768) therefore we were unable to reject our null hypothesis that there was no significant difference between increasing glucose concentrations on mean growth rate.

Effect of Temperature on Glucose Concentration in the Enzymatic Activity of Lactase in Lactose

Katy Hemphil — 2024-09-04

This project was conducted to see the change in enzymatic activity of lactase in the presence of lactose in different temperatures. Our question is: How does the change in temperature impact the glucose concentration as a result of the enzymatic activity of lactase in the presence of lactose? Glucose concentrations were found using OneTouch Ultra 2® blood glucose meter to check the enzymatic activity of lactase. We utilized ANOVA, also known as Analysis of Variance, to check if there were any significant differences in the glucose concentrations between the four different temperature groups of 20°C, 40°C, 60°C, and 80°C. The Lactaid® Extra Strength pills were used as source lactase. At the end, we found there was a significant difference of enzymatic activity between the temperatures. The optimal temperature for the enzymatic activity of lactase was found to be 60°C, and the reactions were too slow to be recorded at lower temperatures. In the future, we can use different brands of lactase, concentration of lactose, and temperatures. This research can help inform our understanding of lactase activity in vivo, the use of lactase in the food industry, including lactose-free products, and in medical applications in treating lactose intolerance.

The Effect of Temperature on Banana Ripening and Ethylene Concentration

Jihee Lee — 2024-09-04

Bananas are a climacteric fruit, so once they are harvested, they enter a “climate phase” where they continue to ripen. Many people can also attest to purchasing green bananas at the supermarket, and waiting for it to ripen over time so it becomes sweet enough to consume. From this universally shared experience, the ripening of the bananas was studied to see temperature as a controllable measure, by adding three banana replicates in three different temperature conditions, of 4ºC, 25ºC, and 40ºC for 5 days. The bananas were monitored and observations were recorded once a day over the duration of the experiment with visual ripeness and mass documentations. Other environmental conditions were controlled by wrapping and storing each banana in plastic wrap to minimise ripening prior to the experiment, and keeping the bananas in incubators of constant temperatures. It was found that bananas at 25ºC were qualitatively closest to the ideal “ripe” yellow colour and bananas at 40ºC had the greatest decrease in weight (ie. released the most amount of ethylene gas) by the end of the 5 days.

Chicken Breast Contamination Removal Efficiency with Different Cutting Boards Materials and Cleaners

Banghua Xu — 2024-09-04

Cutting boards are common tools in the kitchen. Previous studies have shown that different kinds of materials/surfaces have different levels of cleaning difficulties, and different cleaning methods also vary in cleaning efficiency. Here we want to study whether there will be meat contamination after cutting chicken breasts on different materials, including wood, plastic and iron, after applying different cleaning methods, including liquid cleaner, solid cleaner and water. Here we show that only the materials of cutting boards affect the number of meat residuals. Among all three tested, iron cutting boards have the lowest meat residuals. No statistically significant differences were found among different cleaning methods. Our study provides an insight that plastic or wood cutting boards that are commonly used in the home kitchen and restaurant might be a source of cross-contamination.

Investigating the Presence of Contamination in Beef and Chicken from Fast-Food Restaurants, Grocery Stores, and Fine-Dining Restaurants

Nabee Begh — 2024-09-04

The growing and major issue associated with mislabelling and contamination in the meat industry has resulted in a significant threat to food safety. This lack of transparency in the production of meat and packaging of meat administered to consumers has resulted in negligence and poor food safety practices which has contributed to the sale of contaminated meat to consumers due to sellers having to follow less protocols and thus are able to increase their profits more by deceiving others. Our research centralized on examining beef, and chicken meat samples from a grocery store, a fine-dining restaurant, and a fast-food restaurant. We isolated DNA of nine animal species and then added a multiplex PCR and finally analyzed our PCR
results using gel electrophoresis. By comparing fragment sizes, we determined the authenticity of the samples. Our findings showed that meat from both the fast-food restaurant and grocery store sources showed signs of contamination with goat meat, more specifically for grocery store beef sample #1, beef sample #2, and fast-food beef sample #3, while no contamination was detected from meat obtained from the fine-dining restaurant source. It is also worth mentioning that grocery store beef sample #1 and grocery store beef sample #2 had some chicken contamination. Therefore, our study suggests that fine-dining restaurants have a lower incidence of meat contamination than fast-food restaurants and grocery stores, possibly due to better hygienic practices by employees. It is also worth mentioning that this was a single study with a small sample size.

Fungi Spread Affected By Distance From Hand Dryer

Kat Duangkham — 2024-09-04

Hand dryers are commonly installed and used in public washrooms as an alternative to paper towel dispensers, often with the intention of being more environmentally friendly. However, they also have the potential to widely distribute fungi around the washroom environment, which may deposit onto surfaces and get carried from place to place. Using a bread model, this study investigated whether distance from a hand dryer affects the amount of fungi dispersed onto a surface while the hand dryer is running. Various species of mould growth, including Penicillium expansum and Aspergillus flavus, were observed amongst the bread slices. The percent coverage of mould growth on bread slices was tracked over an observational period of 11 days, and an average growth rate for each treatment distance from the hand dryer (n = 4) was calculated. A one-way ANOVA was performed, and determined that differences in growth rate between varied distances from the hand dryer were statistically insignificant (p = 0.1216). There is no difference in the amount of fungi dispersed onto a surface with different distances away from the hand dryer.

The Effects of Thermal Stress Response on Oxygen Production of Chlamydomonas Reinhardtii

Amir Habibi — 2024-09-04

Chlamydomonas reinhardtii is a unicellular photosynthetic alga that is vital for ensuring the health and stability of aquatic ecosystems, specifically that of salmon populations. Temperature is well understood as an environmental factor that influences the ability of algae and plants to photosynthesize. In this study, we aimed to investigate the effect temperature plays on oxygen production in C. reinhardtii, as an indicator of how potential climate change could impact oxygen levels and the health of salmon populations in the future. The optimal temperature range for C. reinhardtii is between 20°C and 32°C. Cultures of C. reinhardtii were incubated at three temperature treatments of 4°C, 20°C, and 35°C for an acclimation period of 30 minutes and an exposure time of 75 minutes. Initial and final temperature and oxygen measurements were recorded, and results reflected no significant difference in oxygen levels between the controls and treatment vials at different temperatures. The statistical analysis using a One-way ANOVA provided a p-value significantly greater than 0.05, therefore we failed to reject our null hypothesis that thermal stress would have no mean effect on oxygen production levels in C. reinhardtii.

Salinity and pH of Nearby Freshwater Puddles and Snow were Unaltered After Roads Have Been De-Iced

Jeon Joseph — 2024-09-04

Road salt has been widely used as a deicing agent during winter, but concerns have been raised about its potential impacts on freshwater ecosystems. Road salts can negatively impact freshwater ecosystems by increasing the salinity levels, which can harm or kill aquatic organisms and alter the composition of the food chain. Additionally, road salts can also affect the water quality and decrease biodiversity in the affected areas. In this study, we investigated the effects of road salt on nearby freshwater puddles to determine if road salting influences the salinity and pH of nearby puddles. We hypothesised that de-icing roads by means of salting would increase the salt concentrations in nearby puddles significantly. We measured pH and salinity immediately after deicing measures were implemented. We sampled water from puddles of 5 different locations of varying distances near main roads that were visibly salted. Contrary to our hypothesis, our results did not show a significant correlation between salinity levels and distance from the road. The measured pH levels were also not significantly correlated with distance from the road.

Effect of Small Intestine pH on The Enzymatic Activity of Lactase in Breaking Down Lactose

Parveen Gill — 2024-09-04

This study aimed to evaluate the enzymatic activity of β-galactosidase (lactase) at different pHs, quantified by reaction rate constants of lactose hydrolysis. Lactose, composed of galactose and glucose, is a fundamental nutrient and primary ingredient in fermentative procedures (Adam et al., 2005). The experiment monitored the glucose levels at various time intervals during lactose hydrolysis reactions to investigate the impact of pH on lactase enzyme activity. Lactaid® Extra Strength pills containing lactase were mixed with 50 mmol/L lactose. We recorded glucose concentrations every 5 minutes for 15 minutes at ~37.5°C to determine lactose hydrolysis reaction rates with enzyme catalysis at pH 5, 6, 7, and 8. Reaction rate graphs were produced to assess the degradation of lactose under varying pH conditions, and rate laws were derived to describe the reactions. The mean rate constant for lactose hydrolysis at pHs 5, 6, 7 and 8 were respectively k = 0.1619 min-1, k = 0.0975 min-1, k = 0.1037 min-1 and k = 0.1804 min-1. The findings demonstrated that reaction kinetics were greater at pH 5 and 8, unlike what we expected. From this, we can conclude that pH does significantly impact lactase activity.

Something’s Fishy: Investigating Tuna Mislabelling Across the Pacific Northwest

Rabiah Dhaliwal — 2024-09-04

Seafood fraud poses a significant problem due to mislabelling having serious health, ethical, economic, and environmental implications. Despite this, it is commonly used as a method to reduce costs and to meet consumer demand. To investigate this issue in the Pacific Northwest, we tested seven unique samples of tuna, sourced from grocery stores and restaurants, for mislabelling. Three replicates each of four fresh samples (one albacore, one Atlantic bluefin, two yellowfin/ahi) and three canned samples (all skipjack) were tested using DNA extraction, PCR, and gel electrophoresis. The results were inconclusive, possibly due to a combination of factors including complications with the gel used, the small sample size, and the presence of metals and preservatives in the canned samples. We recommend future studies replicate the presented experimental design with primers specific to commonly substituted species for each tuna sample. Usage of a larger sample size would potentially result in a statistically meaningful calculation of mislabelled tuna prevalence.

Determining the Optimal Temperature for Pleurotus ostreatus Mycelium Growth

Paniz Ghavimi — 2024-09-04

Pleurotus ostreatus, a widely cultivated mushroom, possesses various economic, nutritional, and environmental values and has been extensively used in the medical field in antioxidants and antitumors. The mycelium, a root-like structure of the mushroom, grows by creating a network of thread-like branching fibres, also known as hyphae, and is mainly composed of chitin, proteins, and cellulose. This study aimed to investigate the optimal temperature for mycelium growth of P. ostreatus between 20℃, 25℃, and 30℃ in agar medium. Circular gills from oyster mushrooms were incubated in these three different temperatures, and the diameter of mycelium expansion was tracked and measured over the span of two weeks. The results indicated that 25℃ was the most optimal temperature for Pleurotus ostreatus mycelium network growth for this experiment. However, several challenges and sources of error were faced throughout the study, such as potential contamination, moisture loss, and light sensitivity, which may have impacted the results. Future studies should consider preventing these sources of error to improve the accuracy of their results. By understanding the most suitable temperature for mycelium growth, their mass production for nutritional or medical uses will be more successful.

Mung Bean Germination Under Select Wavelengths

Rashmi Hundal — 2024-09-04

Mung beans (Vigna radiata) are an inexpensive, sustainable, and essential source of nutrients. Developing optimal methods in germination, such as determining light wavelengths that produce the healthiest seedlings, likely will correlate to protein content and metabolites, and overall a more nutritious bean. This is necessary as many impoverished areas across the world lack accessibility to nutrient-dense ingredients such as animal meat. This experiment had three mung bean groups limited to either red (λ= 680 nm), blue (λ= 410 nm), green (λ= 520 nm), and white light wavelengths. One treatment consisted of a no light control group. The mung beans were germinated under these various light conditions to determine if there would be a significant difference in their final radicle length after one week of light exposure. Statistical analysis showed that there was no significance between the red, blue, green, or white light treatment groups in terms of radicle length. The no light control group displayed significantly greater amounts of radicle growth (p<0.0001).

Keywords: mung beans; germination; wavelengths; radicle growth

When Combined with Household Aluminum Foil, Do Common Cooking Additives Pose Health Risks to the General Public?

Isabel Lucky — 2024-09-04

This study aims to investigate the impact of aluminum foil when exposed to solutions of varying pH (pH = 0 to 14), especially since aluminum leaching can pose serious health concerns. We hypothesized that as the pH of the solution decreases (i.e. solution is more acidic), the average decomposition of aluminum foil into the solution increases after being submerged for 4 days. To test the hypothesis, pieces of aluminum foil were submerged in different common household cooking additives of varying pH: lemon juice (acidic; average pH of 2.45), white vinegar (acidic; average pH of 2.80), water (neutral; average pH of 7.58), and baking soda (alkaline/basic; average pH of 8.78). The selected solutions reflected typical culinary conditions and did not undergo dilution. Results of single-factor ANOVA and Kruskal-Wallis were statistically significant (i.e. p < .05); Tukey-Kramer Honestly Significant Difference (HSD) showed that the acids facilitated the statistical significance. To attain those results, we incorporated procedural changes to our original methodology. Our study ultimately revealed that acidic solutions increased the amount of aluminum foil degradation, thus increasing the risk of aluminum leaching.