Browsing by Author "Narayanan Nair, Mahesh, committee member"

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Open Access
Effects of antimicrobial treatments on food safety, quality and shelf-life of beef
(Colorado State University. Libraries, 2019) Swenson, Joanna Kristine, author; Belk, Keith E., advisor; Woerner, Dale R., advisor; Geornaras, Ifigenia, committee member; Narayanan Nair, Mahesh, committee member; Prenni, Jessica E., committee member
To view the abstract, please see the full text of the document.
Open Access
Sensory quality of cheddar cheese made with bulk starter and direct to vat starter culture
(Colorado State University. Libraries, 2024) Musetti, James, author; Stone, Martha, advisor; Bunning, Marisa, committee member; Narayanan Nair, Mahesh, committee member; Miller, Jeff, committee member; Romero, Dennis, committee member
The production of cheese in the world consumes around 35% of the total milk production and has increased on average by 4% per year over the past 30 years (Fox et al., 2017). Cheddar consumption had modestly and steadily increased in the past several years in the United States and has increased 2.22% from 9.87 pounds per capita to 10.09 pounds per capita (USDA ERS Dairy Data, n.d.). Over the past several decades modernization of cheddar production in the United States has enabled producers to increase throughput with fewer resources resulting in more efficient production and consistent quality. This includes the common practice of standardizing cheese making procedures on a strict timing basis and using reliable and consistent rate and extent of acidification through culture selection and dosage. One such advancement was the development of defined starter cultures produced in a frozen or lyophilized state to be applied directly to the vat as a direct to vat inoculant (DVI) by the cheesemaker. Previously lactic acid bacterial cultures, defined or natural, were propagated by the cheesemaker prior to cheese production by a preceding fermentation of milk or whey and used to inoculate the milk for cheddar production. The current research investigated if any differences in cheddar cheese biochemical and sensory characteristics exist among cheeses made with bulk starter and DVI technologies. Cheeses were produced using bulk starter culture technology, DVI technology, and DVI technology with pre-acidification then ripened for 90 days. The rate and extent of acidification in the process was analyzed with cheese composition, extent of the catabolism of protein and fat during ripening, and sensory characteristics of the cheese analyzed. MANOVA model analysis reported that the treatments had a significant effect on the cheesemaking process (p=0.00381). Coagulation time was the only response found to be statistically significant (p=0.00081) from the process, biochemical, and sensory responses after mixed model analysis was completed. The make data or milk batch was found to have a significant effect on the cheese production process (p=0.00036), biochemistry (p=0.04391), and sensory characteristics (p=0.00002) of the cheeses. Therefore, it can be concluded that there was no difference in cheddar proteolysis, lipolysis, and sensory characteristics in cheeses manufactured with bulk starter and DVI, and there was no difference in cheddar proteolysis, lipolysis, and sensory characteristics in cheeses manufactured with bulk starter and DVI culture preparations with recipe adjustment for coagulation. The null hypotheses cannot be rejected.
Open Access
The effect of trace mineral source on solubility, rumen fermentation characteristics, and trace mineral concentration in protozoa and bacteria of steers consuming a lactation dairy type diet
(Colorado State University. Libraries, 2024) Loh, Huey Yi, author; Engle, Terry, advisor; Narayanan Nair, Mahesh, committee member; Coleman, Stephen, committee member; Torres-Henderson, Camille, committee member
A series of experiments were conducted to investigate the influence of trace mineral (TM) source on TM solubility, rumen fermentation characteristics, and trace mineral concentration in protozoa and bacteria of steer consuming a lactation dairy-type diet. Experiments 3 and 4 were classified as experiments 1 and 2 in chapter 3 for publication purposes in academic journal. In the first experiment, hydroxychloride TM (HTM) and sulfate TM (STM) sources of Cu, Mn, and Zn (n = 4/element/source; N = 24) were incubated separately in water for 24 h. Initial pH was measured after adding the TM to the solution, then the tubes were incubated at 39°C with agitation. After a 24-h incubation, samples were filtered to obtain the filtrate for TM analysis, and final pH readings were taken. Initial pH of each solution was greater (P < 0.03) for HTM compared to STM for all elements. Final pH tended to be greater for Cu (P = 0.09) and Zn (P = 0.07) from HTM compared to STM. Water solubility of Cu, Mn, and Zn from STM was greater (P < 0.01) than HTM sources. These data indicate that TM source influences pH and solubility of Cu, Mn, and Zn in water. In Experiment 2, eight steers fitted with rumen cannula were blocked by body weight and randomly assigned to treatments consisting of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM sources (n = 4/treatment). Steers were individually fed a cracked corn-corn silage-based diet. Treatments were top-dressed daily. Rumen contents were collected at 0, 2, and 4 h post-feeding on d 1 and 14. On d 15, strained ruminal fluid (SRF) and particle-associated microorganisms (PAO) were obtained. Digesta from HTM-supplemented steers has a lesser (P < 0.01) Mn concentration than STM-supplemented steers on d 14 of the trial. Steers supplemented with STM had a greater (P = 0.0016) soluble Cu concentration in the rumen on d 14 than those fed HTM. Zinc was more tightly bound (P = 0.01) to the digesta in HTM-supplemented steers compared to STM on d 14. The data suggest that dietary TM source can affect rumen soluble Cu concentrations and binding strength of Zn to solid digesta. In Experiment 3, three cannulated steers were adapted to a diet formulated to meet the nutrient requirements for lactating dairy cows. Strained RF was obtained by straining rumen content through 2 layers of cheesecloth. Half of the remaining digesta was washed with McDougall's buffer and filtered through 2 layers of cheesecloth to obtain PAO. Both SRF and PAO were filtered again through 8 layers of cheesecloth. Strained RF was mixed with either McDougall's buffer (SRF) or PAO (SRF+PAO) at a ratio of 1:2 or 1:4 and incubated at 39°C for 12 h using the ground basal diet as the substrate. Digestibility of DM was greater (P < 0.05) in digestion tubes containing SRF and SRF+PAO at a 1:2 ratio. In Experiment 4, eight steers fitted with ruminal cannula were blocked by body weight and assigned to one of two treatment groups. Treatments consisted of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either 1) sulfate (STM) or 2) hydroxychloride (HTM) sources. Steers were housed in individual pens and fed the same diet as described in experiment 1. Dietary TM treatments were mixed with dried distillers grains and mixed in the diet by hand, immediately after basal diet delivery. Dietary treatments were fed for 14 d. On day 15, SRF+PAO was collected from each steer (STM-RF and HTM-RF) and used in a series of in vitro crossover experiments. In vitro substrates (S) used were the ground diets consumed by the animals on each treatment (STM-S and HTM-S). Incubations containing HTM-S had greater (P < 0.01) total VFA concentration and propionic acid molar proportions, but lesser (P < 0.01) acetic acid molar proportions than STM-S. Rumen fluid from steers supplemented with HTM had a greater (P < 0.03) total VFA than STM-RF at 24h post incubation. After 12 h post incubation, the molar proportion of propionic acid in HTM-RF was lesser (P = 0.04) than STM-RF. After simulated abomasal digestion, soluble Mn concentration in HTM-S was greater (P < 0.01) than STM-S. These data indicate that the source of trace minerals can influence in vitro rumen fermentation characteristics and Mn solubility under simulated abomasal conditions.