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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Characterizations of oil-in-water (O/W) emulsions containing different types of milk fats prepared using rhamnolipids as emulsifiers : [a thesis presented in partial fulfillment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Auckland, New Zealand] EMBARGOED UNTIL 1 MARCH 2011

Lin, Lu January 2009 (has links)
Emulsions containing three different types of milk fat fractions (MF13, MF27 and MF42) and anhydrous milk fat (AMF) were prepared at oil to water (O/W) ratios of 1:9, 3:7, 5:5 and 7:3 using rhamnolipids as emulsifiers. The prepared emulsions were analyzed for their storage stability and properties (colour, particle size, zeta potential and rheology). The effects of various factors (freezing/thawing, heating, pH, salts and ionic strength) on the stability of emulsions were also investigated. All emulsions prepared with an O/W ratio of 7:3, regardless of the type of milk fat, rendered a highly condensed, semi solid and cream-like substance whereas other emulsions containing less oil were in a liquid form. Among the four different O/W ratios tested, the highest emulsion stability during the storage of 12 weeks was observed from the emulsions containing 1:9 O/W ratios, due to a combine effect of smaller emulsion particle size and lower collision frequency between droplets. Interestingly, the emulsions with 7:3 O/W ratios were found to be more stable than the ones with 5:5 O/W ratios. This might be due to the limited movements of closely-packed emulsion droplets induced by the high oil concentration of 7:3 O/W ratios. The emulsion stability was significantly affected by low pH, especially at lower than pH 4, due to the loss of electrostatic repulsions between droplets leading to droplet coalescence and also possibly due to hydrolysis of rhamnolipid molecules. The presence of salts (NaCl, KCl and CaCl2) also rendered the emulsion unstable. The degree of instability was gradually increased with increasing salt concentrations. CaCl2 had the most significant effect even at a very low concentration. The viscosity of emulsions increased with increasing oil concentration but was not affected by the types of milk fats. Emulsions with 3:7, 5:5 and 7:3 O/W ratios exhibited non-Newtonian and shear thinning flow behaviour. At 7:3 O/W ratios, MF13 exhibited gel-like properties whereas both MF42 and AMF emulsions became more solid-like at higher frequency.
102

Studies on interactions of milk proteins with flavour compounds : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand

Kühn, Janina January 2007 (has links)
Milk proteins are known to bind volatile flavour compounds to varying extents, depending on the nature of the protein and flavour compound. Processing conditions, such as temperature and pH, are also known to have an influence on the interactions between milk proteins and flavour compounds. These interactions cause a great challenge for flavour scientists because they influence the perceived aroma profile of food products significantly, in particular in low-fat food products. The objectives of this research were to develop a headspace solid-phase microextraction (SPME) method followed by gas chromatography with flame ionisation detection (GC-FID) for the investigation of protein-flavour interactions, and to determine binding parameters of the hydrophobic flavour compound, 2-nonanone, to individual milk proteins - namely, β-lactoglobulin (β-lg), α-lactalbumin (α-la), bovine serum albumin (BSA), αs1-casein, and β-casein -, whey protein isolate (WPI), and sodium caseinate. Secondly, it was the aim to compare the binding of the structurally similar flavour compounds - 2-nonanone, 1-nonanal, and trans-2-nonenal – to WPI in aqueous solution, and to investigate the effect of heat and high pressure treatment, and pH on the extent of protein-flavour binding. The final objective was to investigate the in vivo release of the reversibly bound flavour compound, 2-nonanone, from WPI and sodium caseinate using proton transfer-reaction mass spectrometry (PTR-MS), and to understand the effect of viscosity on flavour release in vivo. The binding of the model flavour compound 2-nonanone to individual milk proteins, WPI, and sodium caseinate in aqueous solutions was investigated, using headspace SPME followed by GC-FID. The 2-nonanone binding capacities decreased in the order: BSA > β-lg > α-la > αs1-casein > β-casein, and the binding to WPI was stronger than the binding to sodium caseinate. All proteins appeared to have one binding site for 2-nonanone, except for BSA which possessed two classes of binding sites. The influence of heat treatment, high pressure processing and pH of the protein solutions on the binding of 2-nonanone, 1-nonanal, and trans-2-nonenal to WPI was determined. The binding of these compounds to WPI decreased in the order: trans-2-nonenal > 1-nonanal > 2-nonanone. The binding of 2-nonanone appears to involve hydrophobic interactions only, whereas the aldehydes, in particular trans-2-nonenal, also react through covalent binding. Upon both heat and high pressure denaturation, the binding of 2-nonanone to WPI decreased, the binding of 1-nonanal remained unchanged, while the binding of trans-2-nonenal increased. The binding affinity of the flavour compounds and WPI increased with increasing pH, which is likely to result from pH dependent conformational changes of whey proteins. The in vivo flavour (2-nonanone) release from solutions of WPI and sodium caseinate was investigated using proton-transfer-reaction mass spectrometry. During consumption, 2-nonanone was partly released from WPI, whereas there was no significant release from sodium caseinate. Even after swallowing of the samples, a substantial amount of flavour was detected in the breath, suggesting that the milk proteins interact with the mucosa in the mouth and throat, resulting in a further release of flavour from mucosa-bound proteins. An increase in viscosity of the protein solutions by the addition of carboxymethylcellulose enhanced the release of 2-nonanone from WPI, and resulted in 2-nonanone release from sodium caseinate. This may be due to a thicker coating of the mucosa with the sample solution after swallowing due to the higher viscosity, resulting in additional release of protein-bound flavour. These findings contribute to the knowledge of the interactions that occur between flavour compounds and proteins, which is required to improve food flavouring and to make protein based foods, e.g., low-fat dairy products, sensorily more acceptable to the consumer. The results also emphasize a careful choice of food processing conditions, such as temperature, high pressure or pH to obtain a desirable flavour profile.
103

Modeling heat transfer in butter products : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph. D.) in Bioprocess Engineering, Institute of Technology and Engineering, Massey University, Palmerston North, New Zealand

Nahid, Amsha January 2007 (has links)
Butter keeping quality and pallet physical stability during transport and storage are dependent on the temperature distribution through the product. Understanding these temperature changes are of vital importance for the dairy industry with regard to butter manufacture, storage and shipping. Three dimensional mathematical models of heat transfer were developed to predict thawing and freezing in butter products. These models require accurate thermophysical data as an input. Specific heat capacity and enthalpy of butter with different composition was measured using Differential Scanning Calorimetry. The specific heat capacity of butter differs for cooling and heating operations due to significant supercooling and delayed crystallization of the fat fraction of butter at temperatures well below the equilibrium phase change temperature during cooling. This reduces the heat capacity for cooling relative to that for heating. Thawing of individual blocks of butter was accurately predicted by the conduction only model (no mass transfer limitations) with equilibrium thermal properties giving accurate predictions when the butter was completely frozen before thawing. For partially frozen butter the conduction model with the measured temperature dependent specific heat capacity data for unfrozen butter including melting of some of the fat fraction gave accurate predictions. For freezing it was observed that water in the butter supercools many degrees below its initial freezing point before freezing due to its water in oil structure. Experiments suggested that during freezing release of latent heat observed as a temperature rebound is controlled as much by the rate of crystallisation of water in each of the water droplets as by the rate of heat transfer. A conduction only model including water crystallization kinetics based on the Avrami Model predicted freezing in butter successfully. Simple models with equilibrium thermal properties and nucleation only kinetics (based on homogenous nucleation theory) or the sensible heat only model (no release of latent heat) gave poor predictions. The models for individual blocks were extended to predict heat transfer in butter pallets. A butter pallet contains product, packaging material and the air entrapped between the packaging and butter cartons. Measurements were made for freezing and thawing of full and half pallets at a commercial storage facility and in the University laboratory. Thawing and freezing in wrapped tightly stacked pallets was predicted accurately by the conduction only model with effective thermal properties (incorporating butter, packaging and air) estimated by the parallel model. For unwrapped tightly stacked or loosely stacked pallets there is potential for air flow between the adjacent cartons of butter. An alternative approach was developed which consisted of modeling the pallet on block by block basis using effective heat transfer coefficients for each surface. Different heat transfer coefficients were used on different faces of the blocks depending on the location of the block in the pallet. This approach gave good predictions for both unwrapped tightly stacked and loosely stacked pallets using the estimated effective heat transfer coefficients from the measured data. Further experimental and/or modelling work is required in order to develop guidelines for estimating effective heat transfer coefficient values for internal block face for industrial scenarios.
104

Nucleation and growth of alpha lactose monohydrate : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Process Engineering at Massey University

Mcleod, Jeremy January 2007 (has links)
Lactose represents approximately one third of the total solids in bovine milk. In the dairy industry, lactose is recovered from whey and whey permeates using a crystallisation process that involves both evaporation and a cooling stage. A good understanding of the lactose crystallisation kinetics enables both these processes to be operated at conditions that maximise the yield and minimise capital and processing costs. This study has looked at the nucleation and growth kinetics of the lactose crystallisation process. A model has been produced that can accurately predict the changing concentration profile as lactose is removed, via growth, from an industrial solution. This model incorporated the available literature information and expanded on it where required. The primary nucleation of alpha lactose monohydrate was investigated on the laboratory scale. The work identified the changing relationship, which occurs with increasing supersaturation, as lactose nucleation moves from being dominated by the heterogeneous mechanism to the homogenous mechanism. The absolute supersaturation at which the mechanism changes was found not to be affected by the solution temperature and agitation rate; however the presence of impurities lowered the supersaturation required for homogeneous nucleation. The effect of mixing on the primary nucleation rate was studied in a Rushton turbine agitated vessel and through a Venturi. Increasing the agitation rate increased the frequency of activated molecular collisions but the critical nucleus size remained constant. A strong correlation was found, for both mixing systems, between the nucleation rate and the frequency of vortex shedding.
105

Phenolic characterization and bioactivity of microwave-assisted extracts from edible house crickets (Acheta domesticus)

Maria C Nino Bernal (11553292) 13 October 2021 (has links)
<p>Entomophagy, which is the habit of eating insects, has become relevant in the past few years as it could potentially help reduce current and future food insecurity, due to the highly nutritious and sustainable characteristics of edible insects. In addition to the nutritional content of insects, research on the potential bioactive components of insect extracts has also gained popularity. In this study, extracts from house cricket (<i>Acheta domesticus</i>) from two farms and their corresponding feeds were obtained using a microwave-assisted extraction. Further phenolic characterization led to the identification and quantification of 4-hydroxybenzoic acid, <i>p</i>-coumaric acid, ferulic acid and syringic acid as major phenolic compounds in both <i>A. domesticus </i>extracts as well as both feed extracts. Additionally, <i>in vitro</i> antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl radical cation (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical assays. In both <i>in vitro</i> assays, <i>A. domesticus</i> extracts showed higher antioxidant activity compared to the feeds. Antibacterial activity against <i>E. coli</i> and <i>L. innocua</i> was also evaluated using the microwell method. The <i>A. domesticus </i>extracts showed a selective inhibition (p<0.05) towards the gram-positive bacteria <i>L. innocua </i>between a period of 4 to 8 h. This inhibition is thought to have occurred as a result of the presence of phenolic acids and antimicrobial peptides, while the feed extracts did not exhibit any inhibitory activity towards any of the bacteria. The finding of the same phenolic acids in <i>A. domesticus</i> and their corresponding feed could imply the capacity of <i>A. domesticus</i> to absorb and sequester dietary phenolics that may provide additional health benefits when the insect is consumed, unveiling new benefits of entomophagy. </p>
106

CHARACTERIZATION OF DRY-AGED MEAT FLAVOR PRECURSORS AND LIBERATION MECHANISM THROUGH A METABOLOMICS APPROACH

Derico Setyabrata (11791949) 20 December 2021 (has links)
<p>Within the last decade, the popularity and interest in dry-aging have constantly increased among both consumers and producers. Dry-aging is a natural value-adding process where meat is exposed to a controlled refrigerated environment without any protective barrier during the aging process. This process leads to the development of unique flavors in the final meat product. Although the prevalence of this process is increasing, there are inconsistent reports regarding the impacts of dry-aging on meat sensory attributes, especially on the flavor aspect. Given that flavor generation is dependent on the composition and availability of flavor precursors, the presence or absence of these precursors may contribute to the inconsistency observed. Thus the main objective of the research described here was to characterize the flavor precursors in dry-aged meat and elucidate potential factors or mechanisms favoring to their production.</p> <p> To achieve this objective, metabolomics analysis was conducted in conjunction with various chemical analyses (free amino acids, fatty acids, sugar content and volatile analysis), microbiome profiling and meat quality analysis (tenderness, water holding capacity, color stability, oxidative stability, microbial attributes and sensory analysis) to identify the essential flavor precursors and their production process. In addition, similar analyses were conducted using multiple meat sources (grass-fed beef loins, cull cow beef loins and pork loins) aged by wet-aging (WA), conventional dry-aging (DA), dry-aging in bag (DWA) and UV-light dry-aging (UDA) to elucidate the impact of the different aging treatments on meat quality, sensory attributes and flavor precursor availability.</p> <p>Regardless of the meat source, the results demonstrated that dry-aging altered the meat flavor precursor compositions, primarily by increasing the presence of protein-derived precursors (e.g., free amino acids and dipeptides), especially glutamine and glutamate compounds. Additionally, nucleotide and carbohydrate-derived compounds such as adenosine and reducing sugars were greatly increased after the dry-aging process. While the fatty acid profile was minimally affected, metabolomics analysis revealed a decrease in sterol and terpenoid lipids following dry-aging, which could potentially reduce off-flavors development in the meat. Other compounds such as vitamin B and vitamin C were also detected in the dry-aged product, which potentially could contribute to the flavor development.</p> <p>Analysis of the liberation mechanisms demonstrated that dehydration played a role in increasing the concentration of the flavor precursors in the dry-aged product, potentially promoting greater (e.g., Maillard reaction) during cooking. Furthermore, microorganisms might be responsible for further increasing the availability of flavor precursors in dry-aged meat, especially free amino acids, along with the dehydration process. Microbiome profiling found that <i>Pseudomonas</i> spp. are the most prominent bacterial species in microbial communities found on dry-aged meat which could affect the precursor release in dry-aged meat. Metabolomics analysis also indicated increased glutathione metabolism during dry-aging, which could lead to the liberation of glutamine-related compounds. The analysis also identified other compounds such as porphyrin rings (iron-related) and shikimic acid (bacterial metabolism), providing further examples of how metabolomics can identify dry-aged flavor precursors and reveal other potential mechanisms related to flavor development mechanisms.</p> <p>These outcomes demonstrate that dry-aging alters meat flavor precursor composition, mainly by increasing the availability of protein-, nucleotide- and carbohydrate-derived compounds. Such results indicate that the Maillard reaction is likely be the main mechanism in flavor generation in dry-aged meat. The current results provided more insights into the dry-aging flavor development, especially highlighting important flavor precursor such as glutamate and glutamine containing products, likely to contribute to the dry-aged flavor. Future study to identify the impact of different microorganism (especially mold and yeast) on dry-aging flavor development would be of interest. Additionally, impact of different cooking process should also be studies to maximize the dry-aged flavor potential from the product.</p>
107

PROCESSED MEAT CHARACTERISTICS BETWEEN COMMERCIAL DUROC SIRED AND HERITAGE BREED LARGE BLACK PIGS

Yufei Guo (11798366) 20 December 2021 (has links)
<p>The United States is ranked third for global pork production as well as first in pork exports according to the USDA Economic Research Service in 2019. The majority of the commercial pork production in the United States applies some form of confinement system with environmentally adapted facilities. However, with information and easy media access to the US consumers, news and reports on different farming practices and potential issues in the animal industry have come under the spotlight. Consumers are becoming more interested in knowing what goes on behind the scenes of the commercial animal industry and where and how their food is produced. Whether it is due to personal beliefs, ethical concerns, novelty-seeking, eating experience, or choice of lifestyle, consumers are demanding diversity in their meat purchasing options. Although the commercial pork industry has shifted to fewer and larger farms in the last 40 years, small specialty farms such as heritage breed pork are on the rise to form a niche market. Large Black pig is a pasture-raised heritage breed originating in England, and it remains one of the rarest British pig breeds. Due to differences in husbandry, pasture-raised Large Black pigs consume a relatively high forage diet compared to corn-based diet used in commercial swine production. Although heritage pork has been lauded to have unique and superior quality, enhanced eating experience, and is often sold at a premium price, there are very little data on pork quality of Large Black pig compared to Duroc-sired breeds which are commonly used in commercial pork production. The purpose of this study is to fill the dearth and investigate differences in pork processing characteristics between commercial Duroc-sired and Large Black genetic lines fed high forage or commercial diets.</p><p> The study contained a total of 50 pigs: 25 Duroc-sired (DS) and 25 Large Black sired (LB) pigs. After all the pigs were weighed, the pigs were randomly assigned with heavy and light weights as blocks to two dietary treatments: Fiber (FIB) and Control (CON); and the feeding trial lasted a total of 126 days. There were 14 Large Black pigs fed fiber diet (LB FIB); 11 Large Black pigs fed control diet (LB CON); 14 Duroc-sired pigs fed fiber diet (DS FIB) and 11 Duroc-sired pigs fed control diet (DS CON). Pigs were fed either a control Corn-Soybean Meal-DDGS based diet or a high fiber diet with wheat middlings and dehydrated alfalfa meal replacing corn and soybean meal in the control diet. Diets were fed over six 21 days phases with fibrous ingredient levels increasing from 8.5 to 30 percent of the diet with sequential dietary phase from 1 to 6. Pigs were harvested at a common age with some variations in body weight between genetics (DS 125 ± 2.23 kg, LB 99 ± 2.28 kg; <i>P</i> < 0.001). Individual batches of 80% lean : 20% fat sausage patties with seasoning (136g per patty) were made from the shoulder of each pork carcass. PVC packaging was applied to each batch of sausage patties. Fat smear was noted on day 0 with a fat smear scale of 1 (excessive far smearing) to 8 (clear fat particle definition). Color parameters that include lightness (L*), redness (a*), yellowness (b*), and lipid oxidation (2-Thiobarbituric acid reactive substances, TBARS) due to retail display effect were measured at days 0, 3, and 7 by placing packaged sausage patties under the retail display lighting. Boneless bellies were removed and weighed (fresh weight) from each pig and measurements for belly thickness, length, and firmness were recorded. Fresh bellies were injected to 110% fresh weight, thermally processed (62°C), and cooled (1°C internal temperature). Cooked weight was obtained before slicing. Belly processing yield was calculated as a percentage using (cooked weight / fresh weight) x 100. Adobe Photoshop was used to perform visual image analysis for bacon slice length (SL; cm), slice area (SA; cm<sup>2</sup>), and slice lean area (LA; %), one 0.64 cm bacon slice was obtained from 25, 50, and 75% distance respectively from the blade end of each cooked bellies for the analysis. RStudio (1.2.1335) was used to analyze data with breed and diet as fixed effects and least square means separated at (<i>P</i> < 0.05).</p><p> Results showed that only diet was significant for patty fat smear (<i>P </i>= 0.0104), CON patties had better particle definition than FIB patties. Difference for patty color L* (<i>P </i>= 0.0051), a* (<i>P </i>< 0.0001) and b* (<i>P </i>< 0.0001) were found for days of retail display. Breed was significant in L* (<i>P </i>< 0.0001) and a* (<i>P </i>< 0.0001) with DS patties being lighter and less red than LB patties. Days under retail display (<i>P </i>< 0.0001) and breed x diet interaction (<i>P </i>= 0.0014) were found in lipid oxidation. DS CON had the least amount of lipid oxidation throughout retail display time. Breed and diet were significant for both belly thickness and length. LB (<i>P </i>= 0.0263) and CON (<i>P </i>< 0.0001) bellies were thicker than DS and FIB bellies respectively. DS (<i>P </i>< 0.0001) and CON (<i>P </i>= 0.0045) bellies were longer than LB and FIB bellies respectively. A breed x diet interaction (<i>P </i>= 0.0527) was observed in belly firmness and LB CON had the firmest bellies. Processing yield was found to be greater in DS bellies (<i>P </i>= 0.0014) than LB bellies. Breed effect had a tendency (<i>P </i>= 0.065) on SL, DS slices were longer. CON had greater SA (<i>P </i>< 0.0048) than FIB slices. DS slices had significantly higher LA (<i>P </i>< 0.0001) than LB slices.</p> The study provided novel insights into the differences in processing characteristics between the DS and LB genetic lines as well as the effect of diet on each breed. Results such as thicker and firmer belly, lower LA in LB were expected since LB is a minor swine breed that has not undergone intense genetic selection for percent lean meat. Overall, each breed had a better product when fed their accustomed diet (FIB for LB, CON for DS) such as less lipid oxidation in sausage patties for DS CON compared to LB CON. Although LB fits into the niche market of heritage breed pork, future studies in management systems, processing methods, and genetic improvement should be considered to improve product quality to better meet modern consumer demands.
108

PHYSICOCHEMICAL AND SENSORY EVALUATION OF INVASIVE SILVER CARP (Hypophthalmichthys molitrix) FISH NUGGETS

Joseph L King (8788295) 01 May 2020 (has links)
<p>Silver carp (<i>Hypophthalmichthys molitrix</i>)<b> </b>are an underutilized, invasive fish threatening native species throughout major water systems in the United States. The goal of this research was to use silver carp meat to create a value-added product, to analyze the changes in physicochemical structure and consumer liking over time, and to evaluate the benefits of adding soy, pea, and a combination of soy and pea protein isolates to the formulations. Fish nuggets were prepared from minced meat in four treatments consisting of 3% soy protein isolate (SPI), 3% pea protein isolate (PPI), a combination of 1.5% SPI and 1.5% PPI, and a control without plant protein isolate. Nuggets from each treatment were stored frozen for 1.5, 8.5, and 13.5 weeks. Proximate composition, pH, cook loss, textural hardness, expressible moisture, color, microbial counts and lipid oxidation were evaluated. Sensory acceptability was also evaluated for each frozen storage time period and treatment. A descriptive (QDA<sup>™</sup>) trained sensory panel was also conducted on all treatments independent of the storage testing. Results showed that lipid oxidation and textural hardness significantly (P < 0.05) increased with frozen storage time. PPI had significantly lower expressible moisture compared to the control at week 1.5, but there were no statistically significant differences between treatments at weeks 8.5 and 13.5. Similarly, formulations with PPI improved (p<0.05) cook loss for week 1.5, but not week 8.5 or 13.5. Overall, sensory acceptability did not change (P > 0.05), with the exception of decreased degree of liking scores for SPI aroma (p=0.03) and flavor (p=0.03)) during the frozen storage period; all degree of liking scores remained above 6.5 throughout analysis, indicating that consumers’ acceptability of the sample treatments over time despite the changes in physicochemical structure. The descriptive panel created an attribute lexicon for the aroma, flavor, and mouthfeel of the fish nuggets and did not find significant differences in intensities for those attributes between the treatments. Although there were measurable changes in oxidation, texture, expressible moisture, and cook loss over 13.5 weeks, these changes did not impact sensory acceptance. The addition of protein isolates improved water holding capacity initially but did not maintain those benefits over extended shelf life and had little impact on consumer liking during any time period. Overall, this study demonstrated that value-added products such as silver carp nuggets can be created using an otherwise under-utilized fish. The fish nuggets had high sensory acceptability, and the addition of protein isolates did not significantly improve their sensory characteristics; therefore, silver carp nuggets can be formulated without the need of additional protein additives .</p>
109

INNOVATIVE COLD PLASMA-ASSISTED EXTRACTION FOR BIOACTIVE COMPOUNDS FROM AGRICULTURAL BYPRODUCTS

Yiwen Bao (8232060) 06 May 2020 (has links)
<p>Fruits play a necessary role in the human diet, and their cultivation is important to the prosperity of any country worldwide. However, fruit waste generated in large quantities in agricultural value chain is normally used to feed animals or directly disposed to landfill, ending up with low economic value and a heavy environmental burden. Agricultural waste that contains significant amounts of bioactive compounds can be utilized as byproducts and valorized through bioactives recovery. Conventional bioactive compounds extraction includes intensive uses of organic solvents and also has relatively low efficiency. Therefore, an environment-friendly alternative with higher extraction efficiency is needed. Cold plasma can convert gaseous medium to a highly reacting state with low energy cost, generating reactive species that are able to disrupt cell structures as well as modify material surfaces. This study has developed an innovative cold plasma-assisted extraction technology to enhance the recovery of bioactive compounds from fruit processing byproducts. The objectives of this study are to examine the effects of dielectric barrier discharge plasma on fruit pomaces, in terms of (i) surface microstructure and properties, (ii) extraction efficiency of their bioactive compounds, and (iii) bioactives composition and nutritional value of their extracts.</p><p>High voltage atmospheric cold plasmas (HVACP) generated with different working gases (air, argon, helium and nitrogen) were applied on tomato pomace (TP). In addition to creating ruptures on TP epidermal cells, HVACP treatments were found to decrease the water contact angles of tomato peels and accelerate the drying of tomato fruits, indicating the formation of more hydrophilic surfaces. Helium and nitrogen plasmas-treated TP showed increased PC extraction yields by 10%, and all HVACP-treated samples exhibited higher AA and changes in their phenolic compositions.</p><p>Grape pomace (GP) from red wine production was treated by helium-HVACP for different time periods (5, 10 and 15 min). Similar cell structure disruption and surface hydrophilicity enhancement were observed, and the effects became more significant as treatment extended. HVACP treatment also increased the total phenolic content in GP extracts, by 10.9−22.8%, which contained a higher anthocyanin concentration and showed an improved AA (16.7−34.7%). Furthermore, competitive effects of HVACP treatment on PC extractability enhancement and their degradation were observed.</p><p>The results of this study have proved that HVACP-assisted extraction successfully improved the extraction efficiency of bioactive compounds from fruit pomace and enhanced the nutritional quality of their extracts. This novel technology is a promising method for valorizing different agriculture byproducts into functional food ingredients and nutraceuticals with high nutritional values, which thus can bring significant economic benefits to the agricultural, food and nutraceutical industries.</p>
110

PREBIOTIC POTENTIAL OF A WIDE SELECTION OF TUBERS, GRAINS, AND PULSES IN COMPARISON TO FRUCTO-OLIGOSACCHARIDE

Ahmad Enosh Kazem (9760571) 11 December 2020 (has links)
<p>The most common food and supplement prebiotic fiber is inulin – most commonly extracted from chicory root. Fructo-oligosaccharide (FOS) is a smaller version of inulin, both containing mainly fructose units with β-1,2 linkages. FOS/inulin has been used, and studied, as a prebiotic for decades. The potential of alternative prebiotics intrinsic in whole foods, such as in tubers, grains, vegetables, and pulses – the world’s most common staple crops – are not as commonly recognized as prebiotics, though have this potential if fermentable in the gut. If such alternative sources of prebiotic ingredients could be established it would allow for cheaper, possibly more effective, and more diverse food product development options beyond FOS/inulin. </p> <p>This study demonstrates the potential of tubers, grains, and pulses as prebiotics in relation to their <i>in vitro</i> human fecal fermentation rate, short chain fatty acid (SCFA) production, and microbiota indicators of alpha diversity and impact on key bacterial genera. Fecal samples were obtained from three diverse healthy human donors and used as the initial bacterial inoculum to simulate conditions in the human gut (colon). Substrates (n=35), after undergoing an upper gastrointestinal tract simulated digestion, were fermented by each individual donors’ inoculum separately, and measurements after 6, 12, and 24 h of fermentation were made on gas production, SCFA metabolite production, and microbiome composition. </p> <p>The results of this study establish high fermentability and potential prebiotic effects of dietary fibers from tubers, grains, and pulses. Whole foods, ground and cooked the same way, produced dietary fibers that were largely insoluble, but surprisingly fermentable with high SCFA levels, mostly slow fermentation profiles indicating high tolerability, and mostly promoting diverse microbiota responses compared to FOS. Generally, whole food fibers had higher fermentability than similar isolated fibers. Overall, the processing steps, such as atmospheric or pressure cooking, tested in some pulses did not detract, or add to, the prebiotic abilities of the substrates. Each food fiber substrate had unique effects on the gut microbiota parameters tested. Gut microbiome compositional responses to the same substrate varied significantly among the three donors, but notably SCFA metabolite responses were similar among donors. </p>

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