Influence of Antioxidant Addition and Processing Treatment on the Formation of Lipid Oxidation Compounds in Spray-dried Bovine Plasma Protein

The effects of antioxidant (tert‐butylhydroquinone, propyl gallate, butylated hydroxytoluene, and rosemary) addition, processing treatments, and storage time on the formation of lipid oxidation compounds in spray‐dried bovine plasma protein (BPP) were determined. Lipid oxidation is initiated by spray‐drying; formation of lipid oxidation compounds was highest in BPP processed using a gas‐fired spray‐drier. The most effective antioxidant in inhibiting the formation of hexanal and other lipid oxidation compounds was tert‐butylhydroquinone. Increased spray‐drier residence time and extended storage contributed to increases in lipid oxidation products. Use of effective antioxidants and selection of processing parameters to minimize lipid oxidation reactions can improve the flavor quality of spray‐dried BPP.     

Conjugated Linoleic Acid Content of Cheddar-type Cheeses as Affected by Processing

Samples were taken at 9 stages of processing, from raw milk to cheese aged for 6 mo. Fatty acid distributions, conjugated linoleic acid (CLA), moisture, protein, lipid contents, and titratable acidity were determined. CLA contents were highest after 3 mo, with one type of Cheddar (3.76 mg/g lipid) higher than the other two (3.44 and 3.47 mg/g lipid). Multiple linear regression showed all composition parameters were directly related to CLA content (mg/100 g sample). The content of oleic acid isomer C_18:1ω7 was also directly related to CLA content (mg/g lipid). Thus, content of CLA in Cheddar-type cheeses might be controlled by stage and conditions of processing. An understanding of the effects of processing on CLA formation in Cheddar-type cheeses will be beneficial in designing processing methods to enhance CLA contents.     

Sugars and Free Amino Acids in Stored Russet Burbank Potatoes Treated with CIPC and Alternative Sprout Inhibitors

Glucose, fructose, sucrose and free amino acids were measured in stored Russet Burbank potatoes treated with sprout inhibitors isopropyl-N-(3-chlorophenyl) carbamate (CIPC), 1,4-dimethylnaphthalene (DMN), cineole and salicylaldehyde. Storage effects on sugar and amino acid contents were dependent on the specific sprout inhibitor. Salicylaldehyde treatment (200 ppm) produced a rapid increase of reducing sugar content and a greater amount of free amino acids than other treatments. A smaller amount of tyrosine was found in DMN (40 ppm) treated tubers compared to all other treatments. After 16 wk at 7°C, all potatoes treated with inhibitors had 10.5–11.8 mg/g dry weight reducing sugar content which would be considered acceptable for French fry processing.     

Viability of Bifidobacteria Strains in Yogurt with Added Oat Beta-Glucan and Corn Starch during Cold Storage

Abstract: Probiotics must be consumed at a level of 10⁷ CFU/mL for successful colonization of the gut. In yogurts containing beneficial cultures, the survival of probiotic strains can quickly decline below this critical concentration during cold storage. We hypothesized that beta-glucan would increase the viability of bifidobacteria strains in yogurt during cold storage. Yogurts were produced containing 0.44% beta-glucan (concentrated or freeze-dried) extracted from whole oat flour and/or 1.33% modified corn starch, and bifidobacteria (B. breve or B. longum) at a concentration of at least 10⁹ CFU/mL. All yogurts were stored at 4 °C. Bifidobacteria and yogurt cultures, Streptococcus thermophilus and Lactobacillus delbureckii subsp. bulgaricus, were enumerated from undisturbed aliquots before fermentation, after fermentation, and once a week for 5 wk. S. thermophilus and L. bulgaricus maintained a concentration of at least 10⁸ CFU/mL in yogurts containing concentrated or freeze-dried beta-glucan regardless of starch addition, and in the control with no added beta-glucan or starch. Similarly, the probiotic, Bifidobacterium breve, survived above a therapeutic level in all treatments. The addition of beta-glucan prolonged the survival of Bifidobacterium longum at a concentration of at least 10⁷ CFU/mL by up to 2 wk on average beyond the control. Further, the inclusion of concentrated beta-glucan in yogurt improved survival of B. longum above 10⁷ CFU/mL by 1 wk longer than did freeze-dried beta-glucan. Study results suggest that beta-glucan has a protective effect on bifidobacteria in yogurt when stressed by low-temperature storage. Practical Application: This study suggests that beta-glucan (oat fiber) may improve bifidobacteria survival in yogurt during refrigerated storage.     

Preliminary screening of Bifidobacteria spp. and Pediococcus acidilactici in a Swiss cheese curd slurry model system: Impact on microbial viability and flavor characteristics

A Swiss cheese curd slurry model system was used as a preliminary screening method to determine the feasibility of the incorporation of probiotic bacteria (Bifidobacterium breve R0070, Bifidobacterium infantis R0033, Bifidobacterium longum R0175, and Pediococcus acidilactici R1001) into Swiss cheese. The cheese curd was inoculated with probiotic bacteria (8.0 log₁₀ cfu g⁻¹) and ripened anaerobically for 0, 7, and 10 days at 37 °C. Following ripening, counts of the probiotic bacteria increased to 9–10 log₁₀ cfu g⁻¹, with no significant difference in the viability of the four probiotic bacteria. Viable populations of Swiss cheese background microflora in the presence of each probiotic culture were comparable with the control. Ripening time, and to a lesser extent probiotic treatment had a significant effect on the content of several volatile flavor compounds. Similarly, ripening time contributed to a significant increase in the content of a majority of the free amino acids. The study demonstrated the feasibility of the incorporation of probiotic bacteria into Swiss cheese to produce a functional food.     

Conjugated Linoleic Acid and Fatty Acid Composition of Yogurt Produced from Milk of Cows Fed Soy Oil and Conjugated Linoleic Acid

ABSTRACT: Yogurt was processed from milk from Holstein cows whose diets were supplemented with soy oil (5%) and/or conjugated linoleic acids (CLA, 1%) to determine the effect of processing and dietary supplementation on CLA and fatty acid composition. Processing and storage for 7 d did not significantly affect CLA or fatty acid composition. CLA contents of milk and yogurt increased 2.8- and 2-fold by soy oil and CLA supplementation, respectively. Contents of saturated fatty acids decreased and trans -octadecenoic acids increased with the soy-oil-supplementation. The addition of CLA to soy-oil-supplemented diets did not significantly affect the CLA and fatty acid composition of the yogurt.     

Fibrillar size in native cellulose

Fibrillar size of native cellulose was studied in detail by electron microscopic and x-ray techniques. Samples included natural fibers of cotton and ramie as well as algal and bacterial celluloses. Results indicated smaller sizes for cotton and ramie than was previously reported in the literature and a possible difference in fibrillar sizes among celluloses.