M.S. - Food Science

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https://hdl.handle.net/10125/2061

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    NUTRITIONAL AND PHYTOCHEMICAL COMPOSITION OF PROCESSED HAWAIIAN SEAWEED
    (2024) Xie, Dongjun; Ho, Kacie; Food Science
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    PEA PROTEIN ISOLATE-GREEN TEA CATECHIN PICKERING PARTICLES FOR OIL-IN-WATER (O/W) EMULSION STABILITY
    (2023) Vital de Sousa Junior, Wanderley; Ho, Kacie; Food Science
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    Oscillating Magnetic Field (OMF) And Pulsed Electric Field (PEF)-assisted Supercooling For The Improved Shelf Life Of Fresh Salmon Fillets
    (University of Hawaii at Manoa, 2022) Tang, Jinwen; Jun, Soojin; Food Science
    In recent years, global fish and seafood markets have continued to expand, and seafood demand and transaction volumes have also increased yearly. Due to increasing demands for protein-rich fish products, countries such as China, India, and Indonesia have high consumption of fresh fish products. Meanwhile, salmon, a type of seafood with a broad market volume and potential, has significant shares in terms of revenue in the North American seafood market. As a result, consumers' inclination toward healthy lifestyles and changing dietary habits drive the demand for fish products.However, seafood is extremely perishable partly due to the presence of amino acids, which can decompose into biogenic amines and ammonia. Seafood is also rich in polyunsaturated fatty acids (PUFA), which is easily oxidized and leads to unpleasant odor, taste, nutrient loss, and color changes. Therefore, proper food processing techniques should be employed to maintain the quality of salmon and extend storage time. Freezing is the most common process for the long-term preservation of food. Immobilization of liquid water by lowering the storage temperature can reduce the quality deterioration rate. Freezing temperatures below 0°C also prevent the growth of microorganisms in the food that cause food spoilage and foodborne illness. However, during the freezing process, the initial freezing step forms ice crystals that damage food structures and reduce food quality. Therefore, there is a great need to preserve food without freezing damage. Supercooling is a new food processing technology that keeps food below the initial freezing temperature without forming ice crystals. It provides a longer shelf life for the food while maintaining the quality of the food. In the supercooling protocol developed by Dr. Jun’s lab, ice nucleation during freezing is prevented by the pulsed electric field (PEF) and oscillating magnetic field (OMF). The fundamental is that electric and magnetic fields have potential interference and rotation effects on water molecules present in the food, ultimately associated with the inhibited aggregation of water molecules. As a result of this, I investigated the effects of supercooling technology based on PEF and OMF on the preservation of salmon to extend salmon's storage time while maintain the freshness. Thiobarbituric acid reactive substances (TBARS) values represent quantitative oxidative changes in meat and meat products during storage. Malondialdehyde (MDA) is one of the most commonly used markers of lipid oxidation secondary products. The color index of frozen and refrigerated samples differed significantly (P<0.05) from the original state. Color differences of frozen, refrigerated, and supercooled samples were 4.2, 5.8 and 2.9, respectively. In addition, the TBARS value of the supercooled sample was about 0.96 MDA/kg, which was close to 1.06 MDA/kg of the frozen/thawed sample, but the value of the refrigerated sample was 2.13 MDA/kg. Meanwhile, the drip loss for the refrigerated samples reached as high as 4% and 2.5%, while the supercooled sample was as low as 0.9%, which was not frozen/thawed or damaged by ice, resulting in little change in drip loss. For the microbial enumeration experiments, after 10 days of experimentation, the microbial counts of all samples increased, the microbial counts of supercooled samples, refrigerated sample, and frozen/thawed samples were 5.4, 6.4, and 5.9 log CFU/ml, respectively. After the experiment of PEF and OMF-assisted supercooling treatment of salmon, our result showed that supercooling treatment could increase the storage time of salmon without quality degradation.
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    Effects Of Supercooling-assisted Freezing On Physical And Structural Properties Of Agar Gel And Tofu
    (University of Hawaii at Manoa, 2022) Wang, Yijing; Jun, Soojin; Food Science
    Supercooling is the process of lowering the temperature of the product below its typical freezing point without forming ice crystals. Compared with well-known long-term preservation methods such as freezing, supercooling can slow down changes in food qualities and also shorten the processing time, reduce energy consumption, and potentially carbon emissions. During the supercooling process, the combined electric field and magnetic field treatments could enhance the mobility of water molecules while at freezing temperature ranges. Pulsed electric fields (PEF) have been reported to reorient and realign water molecules because of the electric dipole present in water molecules. Oscillating magnetic fields (OMF) vibrate water molecules due to water diamagnetism, preventing ice crystal nucleation. The purpose of this study was to evaluate the effect of the supercooling pretreatment before freezing on the physical and structural properties of solid model foods.In this experiment, agar gels (2% agar powder & 10% maltodextrin) and firm tofu were treated using four different methods: freezing at -18℃ for 24 hours, freezing at -18℃ for 24 hours with 6 hours of supercooling pre-treatment, freezing at -80℃ for 24 hours, and freezing at -80℃ for 24 hours after 6 hours of supercooling pre-treatment. The supercooling temperature of agar gel is about -6℃, and firm tofu was supercooled about -2℃. Before treatments, all samples were stored in a refrigerator at 4℃. Their syneresis and texture were measured after thawing for 24 hours. Microscopic observation and micro-CT scanning of the samples were committed at the same time. The results showed that compared with control samples, samples after supercooling treatment showed low syneresis, and the peak force was close to fresh samples. By analyzing the structure of the samples treated under different storage conditions, it was found that the ice crystal of the samples stored at -80°C were finer and denser than that of the samples stored at -18°C. This study proved that the supercooling pretreatment before freezing is beneficial in reducing the damage of ice crystals in the internal structure of the sample and can maintain post thawing physical properties as close to fresh samples. The experimental results of agar gels and firm tofu can serve as a foundation for the supercooling and freezing experiments of more complicated food materials in future studies.
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    Nutritional and Phytochemical Content of Underutilized Taro Cultivars From Hawai‘i
    (University of Hawaii at Manoa, 2021) Senga, Kento; Ho, Kacie; Food Science
    Taro (Colocasia esculenta) is a starchy root crop that is commonly found in most tropical climates around the world. In Hawai‘i, various taro cultivars exist, each with potentially unique nutritional and phytochemical profiles as a result of their pigmented coloration. However, not much is known about the nutrient and phytochemical properties of these cultivars. The primary purpose of this research is to identify the nutritional and phytochemical aspects in these underutilized taro cultivars from Hawai‘i. The nutrient (proximate and mineral), phytochemical (carotenoid, total phenolic, and total monomeric anthocyanin), and digestibility (bioavailability & bioaccessibility) content of two commercially underutilized taro, Mana Ulu & Pi‘iali‘i, were compared with a commercial variety, Maui Lehua. An immature (colloquially referred to as “Keiki”) Pi‘iali‘i corm was also utilized in this study and compared to the other three. Both raw and cooked forms, through steaming, were utilized in this experiment. Overall findings indicated variation in nutrient and phytochemical content across each taro cultivar. Notable distinctions include a higher carbohydrate content found in the Maui Lehua and Mana Ulu cultivars, 31.92% and 31.76% respectively, while Pi‘iali‘i and the Keiki exhibited a lower content of 16.34% and 15.68%, respectfully. Phytochemical identification determined beta-carotene and lutein as the primary carotenoid compounds across each cultivar. Loss of carotenoid content was observed in all cultivars during their transition from raw to cooked states. Following in vitro digestion, only beta-carotene was retained from the cooked Mana Ulu variety. Bioaccessibility testing indicated a digestive stability of 45.8% and a micellarization efficiency of 13.6% for beta-carotene. Values of total phenolic content reported 83.52, 76.04, 75.44, and 66.86 mg/100 g FW and total anthocyanin content of 10.02, 9.33, 7.32, and 6.93mg/100g FW for Maui Lehua, Mana Ulu, Pi‘iali‘i Keiki, and Pi‘iali‘i, respectively. Cooked taro had significant polyphenol losses with total phenolic contents of 20.55, 17.73, 22.61, 25.93mg/100g FW as well as total anthocyanin contents of 3.19, 2.16, 2.12, and 2.88 mg/100g FW for Maui Lehua, Mana Ulu, Pi‘iali‘i Keiki, and Pi‘iali‘i, respectively. This research can provide a significant insight into the utilization of nutrients in underutilized food crops that would otherwise be absent in conventional crop utilization. This can apply not only to taro cultivars in Hawai‘i but other food sources around the world that have different species varieties.
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    Enhanced viability of freeze-dried Lactobacillus acidophilus using supercooling pretreatment
    (University of Hawaii at Manoa, 2021) Wang, Yu; Jun, Soojin; Food Science
    Viability loss during the freezing process remains a big challenge for freeze-dried lactic acid bacteria. Oscillating magnetic field (OMF)-assisted supercooling pretreatment was studied and validated for the improving the viability of freeze-dried L. acidophilus. OMF-assisted supercooling decreased supercooling temperature to -7 °C without ice crystallization, while one of the reference groups without OMF assistance was frozen at -7 °C. Supercooling pretreatment increased surface layer protein (SLP) expression and improved cell viability. The SLP on supercooling pretreated cells was thicker than those without supercooling pretreated cells. Supercooling pretreatment significantly increased the viability of L. acidophilus after freeze-drying compared to those that did not undergo a pretreatment. The highest viability of 78% was observed after freeze-drying with supercooling pretreatment. SLP expression during pretreatment protected cells in the freezing process and helped maintain cell viability. These results suggested that OMF-assisted supercooling pretreatment enhanced the viability of freeze-dried L. acidophilus.
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    Biochemical changes in the development of alcoholic fermented products from taro (Colocasia esculenta)
    (University of Hawaii at Manoa, 1987) Cai, Tiande; Food Science
    Biochemical changes in the development of alcoholic fermented taro products were investigated under different fermentation conditions. The products were prepared by fermenting steamed taro grits with powdered commercial Chinese yeast ball (rice ball) . So