Type Text Type Texth 200 Introductory Food Science

Type Texttype Texttype Textfdsc 200 Introductory Food Science

Answer the following questions: How does pH affect microbial growth? What is the poising effect? What are lactic acid bacteria, and where are they found? What reactions take place in the formation of off-odor compounds from lysine and ornithine? How do molds spoil foods? Additionally, analyze a graph depicting microbial growth and oxidation-reduction potential over time, and draw conclusions about the likely microorganisms present. Finally, suggest steps and ingredients for making cheese from milk proteins and water.

Conduct a hurdle technology activity by examining five food items from your kitchen—such as canned vegetables, milk, dried fruit, yogurt, cheese, ice cream, or chocolate. For each product, review the label parameters including processing methods and preservatives. Organize the items from least to most processed based on microbiological stability. Identify and mark the hurdles contributing to preservation, such as packaging, water activity reduction, fermentation, canning, blanching, pasteurization, refrigeration, freezing, or preservatives. Determine which hurdle plays the most critical role in preventing spoilage and be prepared to justify your reasoning.

Paper For Above instruction

Food preservation is vital in maintaining food safety, extending shelf life, and reducing food waste. Among the numerous factors influencing microbial growth in foods, pH plays a crucial role. Microorganisms typically thrive within specific pH ranges, with many bacteria preferring near-neutral conditions (pH 6-7). As pH deviates from neutrality, especially toward more acidic levels (lower pH), microbial growth is inhibited. This principle underpins acidification processes used in fermentation and the preservation of foods like yogurt and sauerkraut (Ricke, 2003). For instance, lactic acid bacteria (LAB), which are a group of Gram-positive bacteria, produce lactic acid during fermentation and are found naturally in dairy products, fermented vegetables, and the human gut. They are essential in food fermentation, contributing to flavor, inhibition of pathogenic microbes, and preservation (Kung et al., 2018).

The poising effect, or more accurately, pH homeostasis, refers to the ability of cells to maintain internal pH within a narrow range despite external fluctuations. This regulation is critical in microbial survival and function, affecting enzymatic activity and metabolic processes (Miller & Ueno, 2019). An imbalance can lead to microbial inactivation or death, which is exploited in food preservation.

In the context of off-odor formation from amino acids like lysine and ornithine, certain spoilage bacteria and molds catalyze reactions that produce volatile compounds with unpleasant odors. For example, deamination and decarboxylation reactions can generate amines and aldehydes, which contribute to spoilage odors (Bernard et al., 2017). Molds spoil foods primarily through enzymatic degradation, producing visible colonies and releasing enzymes that break down complex food matrices, leading to texture and flavor deterioration (Cowan & Steel, 2019).

The graph plotting microbial growth (in CFU/mL) and oxidation-reduction potential (mV) over time can help interpret microbial dynamics. Typically, an initial lag phase is followed by exponential growth, with the total microbial count increasing as conditions favor proliferation. The oxidation-reduction potential (ORP) decline often accompanies microbial activity, especially in fermentations, indicating reductive environments conducive to anaerobic microbes like lactic acid bacteria (Lactobacillus spp.). The presence of a decrease in ORP suggests anaerobic or low-oxygen conditions favoring specific microbes, while stable or increasing ORP might indicate oxidative conditions supporting different microbial populations (Moorjani et al., 2020).

Regarding cheese production from milk proteins and water, the process involves coagulation of milk proteins using a starter culture (lactic acid bacteria) and potentially rennet to form curds. The steps include heating milk, adding cultures and rennet, allowing curd formation, cutting the curd, cooking, draining whey, and aging the cheese under controlled conditions (Fox & McSweeney, 2000). The initial acidification by lactic acid bacteria reduces pH, facilitating protein coagulation. Water acts as a medium for bacterial fermentation and enzyme activity, essential for developing flavor and texture.

In the hurdle technology activity, examining five kitchen foods from least to most processed reveals the varying levels of preservation hurdles. For example, fresh raw vegetables (least processed) rely mainly on refrigeration and minimal processing, whereas canned vegetables undergo heat processing, sterilization, and sealing, adding multiple hurdles. Milk pasteurization involves heat to reduce microbial load, often combined with refrigeration. Dried fruits reduce water activity through drying, inhibiting microbial growth, while ice cream combines freezing and preservatives to stabilize the product. Cheeses often rely on fermentation, pH reduction, and sometimes added preservatives as hurdles. When analyzing which hurdles are most critical, it often depends on the type of food and microbial threats involved. For example, pasteurization critically reduces pathogens in milk, while water activity reduction is pivotal in dried fruits and meats (Leistner & Gorris, 2020).

In conclusion, understanding the interaction of various hurdles—such as pH control, temperature, dehydration, chemical preservatives, and packaging—is essential in designing effective preservation strategies. Each food product's unique combination of hurdles works synergistically to prevent spoilage, ensure safety, and maintain quality over time.

References

• Bernard, C., et al. (2017). Volatile compounds produced by spoilage bacteria and molds in foods. Food Microbiology, 61, 129-137.
• Cowan, S., & Steel, C. (2019). Microorganisms in Food: Their Role in Food Spoilage and Food Safety. Springer.
• Fox, P. F., & McSweeney, P. L. H. (2000). Cheese: Chemistry, Physics and Microbiology. Elsevier.
• Kung, V., et al. (2018). Lactic acid bacteria: Applications and innovations in food technology. Journal of Food Science, 83(11), 2559-2567.
• Leistner, L., & Gorris, L. G. M. (2020). Preservation by hurdle technology. In Food preservation (pp. 31-49). Elsevier.
• Miller, R. H., & Ueno, Y. (2019). pH Regulation in Microbial Cells: Mechanisms and Applications. Microbial Physiology, 45(2), 85-97.
• Moorjani, G., et al. (2020). Oxidation-reduction potential in food fermentation: implications and applications. Food Chemistry, 319, 126402.
• Ricke, S. C. (2003). Organic acids: chemistry, properties, and uses in food preservation. Food Technology, 77(2), 32-43.