R.L. Bradley

Moisture and Total Solids Analysis

Moisture assays can be one of the most important analyses performed on a food product and yet one of the most difficult from which to obtain accurate and precise data, for reasons described in this chapter. The first sections of this chapter describe both direct and indirect methods for moisture content analysis: instrumentation, principles, procedures, applications, cautions, advantages, and disadvantages. The choice of moisture analysis method is often determined by the expected moisture content, nature of other food constituents (e.g., highly volatile, heat sensitive), equipment available, speed necessary, accuracy and precision required, and intended purpose (e.g., regulatory or in-plant quality control). Latter parts of this chapter describe water activity measurement, since it parallels the measurement of total moisture as an important stability and quality factor. Determining both the water content and the water activity of a food provides a complete moisture analysis. Also included in the chapter is a major section on moisture sorption isotherms. With an understanding of the techniques described in this chapter, one can apply appropriate moisture analyses to a wide variety of food products.

Identification and control of processing variables that affect the quality and safety of fluid milk

The objective of this study was to increase quality and safety of fluid milk by eliminating postpasteurization contamination as measured by extended shelf life. Milk shelf life was defined as the number of days for standard plate count to reach 20,000 CFU/ml in milk stored at 7 degrees C. Sequential analysis of the fluid milk processing system indicated filling machine and pasteurizer were significant sources of postpasteurization contamination. Aseptically sampled milk from the pasteurizer outlet indicated a maximum shelf life of more than 30 days could be achieved. The pasteurizer can be a source of contamination when inadequately cleaned or maintained. The filling machine was a significant source of contamination. Shelf life of milk in 236-ml containers was reduced 20 days compared with milk sampled before the filling machine. Carton-forming mandrels, filling heads, and airborne microorganisms were sources of contamination within the filling machine. Eliminating sources of postpasteurization contamination and proper cleaning followed by sanitizing with chlorine significantly increased milk shelf life in paperboard containers to 20.4 days from an initial shelf life of 9 days. Changing the sanitizing agent to peroxyacetic acid significantly increased milk shelf life to 33.9 days. Enclosing the filling chamber and adding sterile laminar flowing air significantly improved microbiological quality of air inside the chamber and reduced variance among milk shelf life samples.

Raising marketable yellow perch on a polychlorinated biphenyl contaminated diet: a feasibility study for the perch aquaculture industry.

The objective was to determine the feasibility of feeding yellow perch a PCB-contaminated diet without adversely affecting their rate of growth and without exceeding 5 ppm in the fillet. To determine the extent to which the fillet (skeletal muscle and skin) accumulates PCB, assessment was made of the whole body elimination and tissue distribution of a single PCB isomer [14C] 2,5,2′,5′-tetrachlorobiphenyl (4-CB) in fingerling and adult perch exposed to a single oral dose of 0.8 μg of [14C] 4-CB. Elimination and distribution of 4-CB was determined at regular intervals for five weeks after dosing. Fingerlings were found to eliminate 4-CB more rapidly than adults but the tissue distribution pattern of 4-CB residues not eliminated was similar in the two age groups. The carcass and viscera contained about 85% of 4-CB residues in the whole fish and 15% in the fillet. For chronic exposure to PCB-contaminated diets, perch fingerlings were reared under standardized aquaculture conditions that provided an optimal rate of growth. They were fed for 32 weeks either a control diet containing 0.2 ppm PCB or an experimental diet formulated from alewife meal that contained 1.8 ppm PCB. The data showed that growth of perch on the two diets was similar and that PCB concentrations in harvested fillets was less than 0.7 ppm. The significance of these findings is that the perch aquaculture industry may be able to feed lower cost PCB-contaminated diets and still harvest yellow perch fillets that meet U.S. Food and Drug Administration guidelines of 5 ppm for human food.

Efficacy of Sanitizers Using Unsoiled Spiral-Wound Polysulfone Ultrafiltration Membranes1

Sanitizing ultrafiltration and reverse osmosis systems poses unique problems for the dairy industry. Ultrafiltration and reverse osmosis membranes must be held wet and microorganisms remaining within the system could multiply under these conditions unless the holding solution is sufficiently microstatic. Two polysulfone ultrafiltration membranes as obtained from the manufacturer were used to evaluate cleaners and sanitizers. Because these membranes had not been used for processing there were no soil removal problems to interfere with sanitization. The ultrafiltration system was sanitized by recycling solutions for 10 min, and the unit containing sanitizer left idle 16 h. Stainless steel surfaces were examined by swabbing the next morning to check hygiene. Antibac B (50 ppm available chlorine), H2O2 (0.2%, v/v) and an acid anionic surfactant (pH 2.5) were evaluated as sanitizers. None proved satisfactory based on microbiological criteria. Also, there was a loss in available chlorine from Antibac B solutions when held overnight in the retentate housing. These same problems were evident when sanitizers were circulated after cleaning solutions. Permeate flux, when used as a criterion for system cleanliness, indicated adequate cleaning and sanitization. Inability to contact all areas of membranes may be a problem in satisfactory sanitization of an ultrafiltration system.

Fast Generation of Functional Subtype Astrocytes from Human Pluripotent Stem Cells

Summary Differentiation of astrocytes from human pluripotent stem cells (hPSCs) is a tedious and variable process. This hampers the study of hPSC-generated astrocytes in disease processes and drug development. By using CRISPR/Cas9-mediated inducible expression of NFIA or NFIA plus SOX9 in hPSCs, we developed a method to efficiently generate astrocytes in 4–7 weeks. The astrocytic identity of the induced cells was verified by their characteristic molecular and functional properties as well as after transplantation. Furthermore, we developed a strategy to generate region-specific astrocyte subtypes by combining differentiation of regional progenitors and transgenic induction of astrocytes. This simple and efficient method offers a new opportunity to study the fundamental biology of human astrocytes and their roles in disease processes.

Use of a Fertile Egg Injection Technique to Assess Toxicity of Chlorinated Compounds Found in Drinking Water1

Screening of contaminants found in drinking water and those used to render water potable showed none to be extremely toxic. Other contaminants varied in toxicity from practically non-toxic to highly toxic. Sanitizers used in the food industry, sodium hypochlorite and iodophor, while presenting slight to moderate toxicity in undiluted concentrations, showed insignificant toxicity at use levels.

Mutations in GFAP Disrupt the Distribution and Function of Organelles in Human Astrocytes

SUMMARY How mutations in glial fibrillary acidic protein (GFAP) cause Alexander disease (AxD) remains elusive. We generated iPSCs from two AxD patients and corrected the GFAP mutations to examine the effects of mutant GFAP on human astrocytes. AxD astrocytes displayed GFAP aggregates, recapitulating the pathological hallmark of AxD. RNA sequencing implicated the endoplasmic reticulum, vesicle regulation, and cellular metabolism. Corroborating this analysis, we observed enlarged and heterogeneous morphology coupled with perinuclear localization of endoplasmic reticulum and lysosomes in AxD astrocytes. Functionally, AxD astrocytes showed impaired extracellular ATP release, which is responsible for attenuated calcium wave propagation. These results reveal that AxD-causing mutations in GFAP disrupt intracellular vesicle regulation and impair astrocyte secretion, resulting in astrocyte dysfunction and AxD pathogenesis.

A 100-Year Review: A century of dairy processing advancements—Pasteurization, cleaning and sanitation, and sanitary equipment design

Over the past century, advancements within the mainstream dairy foods processing industry have acted in complement with other dairy-affiliated industries to produce a human food that has few rivals with regard to safety, nutrition, and sustainability. These advancements, such as milk pasteurization, may appear commonplace in the context of a modern dairy processing plant, but some consideration of how these advancements came into being serve as a basis for considering what advancements will come to bear on the next century of processing advancements. In the year 1917, depending on where one resided, most milk was presented to the consumer through privately owned dairy animals, small local or regional dairy farms, or small urban commercial dairies with minimal, or at best nascent, processing capabilities. In 1917, much of the retail milk in the United States was packaged and sold in returnable quart-sized clear glass bottles fitted with caps of various design and composition. Some reports suggest that the cost of that quart of milk was approximately 9 cents-an estimated

A 100-Year Review: Milestones in the development of frozen desserts

2.00 in 2017 US dollars. Comparing that 1917 quart of milk to a quart of milk in 2017 suggests several differences in microbiological, compositional, and nutritional value as well as flavor characteristics. Although a more comprehensive timeline of significant processing advancements is noted in the AppendixTable A1 to this paper, we have selected 3 advancements to highlight; namely, the development of milk pasteurization, cleaning and sanitizing technologies, and sanitary specifications for processing equipment. Finally, we provide some insights into the future of milk processing and suggest areas where technological advancements may need continued or strengthened attention and development as a means of securing milk as a food of high safety and value for the next century to come.

Determination of Ice Crystal Size Distributions in Frozen Desserts

Ice cream has come a long way since the first snow cone was made. Innovations in a variety of areas over the past century have led to the development of highly sophisticated, automated manufacturing plants that churn out pint after pint of ice cream. Significant advances in fields such as mechanical refrigeration, chilling and freezing technologies, cleaning and sanitation, packaging, and ingredient functionality have shaped the industry. Advances in our understanding of the science of ice cream, particularly related to understanding the complex structures that need to be controlled to create a desirable product, have also enhanced product quality and shelf stability. Although significant advances have been made, there remain numerous opportunities for further advancement both scientifically and technologically.