Drivers of choice for fluid milk versus plant-based alternatives: What are consumer perceptions of fluid milk?

Fluid milk consumption has declined for decades while consumption of nondairy alternatives has increased. A better understanding of why consumers purchase fluid milk or nondairy alternatives is needed to assist increased sales of milk or maintain sales without further decline. The objective of this study was to determine the extrinsic attributes that drive purchase within each product category. The second objective was to determine the personal values behind the purchase of each beverage type to give further understanding why particular attributes are important. An online conjoint survey was launched with 702 dairy consumers, 172 nondairy consumers, and 125 consumers of both beverages. Individual means-end chain interviews were conducted with fluid milk consumers (n = 75), plant-based alternative consumers (n = 68), and consumers of both beverages (n = 78). Fat content was the most important attribute for dairy milk followed by package size and label claims. Consumers of fluid milk preferred 1 or 2% fat content, gallon, or half-gallon packaging, conventionally pasteurized store-brand milk. Sugar level was the most important attribute for plant-based beverages, followed by plant source and package size. Almond milk was the most desirable plant source, and half-gallon packaging was the most preferred packaging. Means-end chain interviews results suggested that maintaining a balanced diet and healthy lifestyle was important to all consumer groups. Lactose free was an important attribute for plant-based alternative consumers and consumers of both dairy and nondairy. A distinguishing characteristic of those who only drank nondairy plant-based alternatives was that plant-based beverages contributed to a goal to consume less animal products, beliefs about animal mistreatment, and perceived lesser effect on the environment than fluid milk. Unique to fluid milk consumers was that fluid milk was perceived as a staple food item. These results suggest that the dairy industry should focus on the nutrition value of milk and educating consumers about misconceptions regarding dairy milk. Future beverage innovation should include the development of lactose-free milk that is also appealing to consumers in flavor.

Salty taste in dairy foods: can we reduce the salt?

Sodium can be found in many sources of the US diet. Dietary guidelines currently suggest a maximum intake of 2,300 mg of sodium (6g of sodium chloride) per day, whereas the average consumer intake is 3,600 mg of sodium (9 g of sodium chloride) per day. The main health concern with high consumption of sodium is hypertension. The objectives of this study were to identify the salty taste intensity of sodium chloride in water and various dairy food matrices, and to identify the just-noticeable difference in concentration at which consumers noticed a decrease in salty taste in these food products. Solutions and food products (water, cheese sauce, cottage cheese, and milk-based soup) were prepared with sodium chloride ranging in concentration from 0.008 to 0.06 M. Seventeen panelists evaluated the salty intensity of each product in triplicate using a magnitude estimation scale. In subsequent tests, panelists (n=50) evaluated salty intensity of these food products in separate sessions using an ascending force choice method to determine the just-noticeable difference. Consumer acceptance tests (n=75 consumers) were conducted with cottage cheeses with and without sodium reductions and under conditions with and without health benefits of sodium reduction. The magnitude estimation scale data were log-transformed, and all data were analyzed by ANOVA with Fisher's least significant difference for means separation. The linear proportion of the power function in the salty taste intensity curve for sodium chloride solutions and the 3 foods was between 0.03 and 0.20 M. Consumers were able to notice and correctly identify reductions in salt concentration of less than 20% in all products. When consumers were informed of sodium reduction and its health benefits before tasting cottage cheese with lower sodium (4-12%), overall liking scores for the lower sodium cottage cheeses were not different from higher sodium cottage cheeses. These results suggest that reducing sodium in cheese sauce, cottage cheese, and milk-based soups may be challenging and that exploration of sodium chloride alternatives in these foods is warranted. Appropriate product positioning or advertising may be beneficial to consumer acceptance of lower sodium types of products.

Comparison of two methods to explore consumer preferences for cottage cheese.

In the past 2 decades, total sales of cottage cheese have declined 17% despite increases in sales for low-fat cottage cheese. There are no recent published studies investigating consumer preferences for cottage cheese. This study was conducted to identify and define sensory characteristics of commercial cottage cheese and to compare 2 approaches for characterizing consumer preferences: traditional preference mapping and a new composite qualitative approach, qualitative multivariate analysis (QMA). A sensory language was identified to document the sensory properties (visual, flavor, and texture) of cottage cheeses. Twenty-six commercial cottage cheeses with variable fat contents (4, 2, 1, and 0% fat) were evaluated by trained panelists using the sensory language. Eight representative cottage cheeses were selected for consumer acceptance testing (n = 110) and QMA with consumer home usage testing (n = 12), followed by internal and external preference mapping to identify key drivers. Principal component analysis of descriptive data indicated that cottage cheeses were primarily differentiated by cooked, milkfat, diacetyl, and acetaldehyde flavors and salty taste, and by firmness, smoothness, tackiness, curd size, and adhesiveness texture attributes. Similar drivers of liking (diacetyl and milkfat flavors, smooth texture, and mouthcoating) were identified by both consumer research techniques. However, the QMA technique identified controversial distinctions among the cottage cheeses and the influence of brand and pricing. These results can be used by processors to promote cottage cheese sales.

Mapping differences in consumer perception of sharp cheddar cheese in the United States.

There is tremendous variability in flavor profiles of sharp or aged U.S. cheddar cheese due to varied practices among commercial facilities and the lack of legal definitions for these terms. This study explored U.S. consumer perception and liking of commercial sharp or aged cheddar cheese profiles. Flavor profiles of 29 representative sharp cheddar cheeses were documented by descriptive sensory analysis with a trained panel. A total of 9 representative cheddar cheeses were selected and evaluated by consumers in 3 regional locations: east coast (Raleigh, N.C.; n = 150), midwest (Champaign, Ill.; n = 75), and west coast (Pullman, Wash.; n = 100). Consumers assessed the cheeses for overall liking and other consumer liking attributes. External preference mapping revealed 5 distinct consumer segments. The segment membership distribution between east coast and midwest consumers was similar while the west coast distribution was distinct (P < 0.05). A larger proportion of west coast consumers were present in segment 3, which consisted of consumers with specific likes for cheeses characterized by intense flavors of free fatty acid, brothy, and nutty flavors and salty and sour tastes. Consumer preferences in other segments differed from segment 3 due to their liking of at least 1 sensory attribute generally associated with young or mild cheddar cheese flavor. Key drivers of liking for these segments included whey flavor for segments 1 and 4 and milkfat flavor for segment 5. Segment 2 consumers liked most of the cheeses tested except those with dominant whey flavor. A sharp or aged cheddar cheese label means different things to different consumers and liking profiles are not defined by consumer location.

Consumer preferences for mild cheddar cheese flavors.

Flavor is an important factor in consumer selection of cheeses. Mild Cheddar cheese is the classification used to describe Cheddar cheese that is not aged extensively and has a "mild" flavor. However, there is no legal definition or age limit for Cheddar cheese to be labeled mild, medium, or sharp, nor are the flavor profiles or flavor expectations of these cheeses specifically defined. The objectives of this study were to document the distinct flavor profiles among commercially labeled mild Cheddar cheeses, and to characterize if consumer preferences existed for specific mild Cheddar cheese flavors or flavor profiles. Flavor descriptive sensory profiles of a representative array of commercial Cheddar cheeses labeled as mild (n= 22) were determined using a trained sensory panel and an established cheese flavor sensory language. Nine representative Cheddar cheeses were selected for consumer testing. Consumers (n= 215) assessed the cheeses for overall liking and other consumer liking attributes. Internal preference mapping, cluster analysis, and discriminant analysis were conducted. Mild Cheddar cheeses were diverse in flavor with many displaying flavors typically associated with more age. Four distinct consumer clusters were identified. The key drivers of liking for mild Cheddar cheese were: color, cooked/milky, whey and brothy flavors, and sour taste. Consumers have distinct flavor and color preferences for mild Cheddar cheese. These results can help manufacturers understand consumer preferences for mild Cheddar cheese.

Sources of umami taste in Cheddar and Swiss cheeses.

Umami plays an important role in the flavor of many cheese varieties. The purpose of this study was to identify the compound(s) responsible for umami taste in Cheddar and Swiss cheeses. Four Cheddar and 4 Swiss cheeses (two with low umami intensity and two with high umami intensity from each type) were selected using a trained sensory panel. Monosodium glutamate (MSG), disodium 5'-inosine monophosphate (IMP), disodium 5'-guanosine monophosphate (GMP), sodium chloride, lactic acid, propionic acid, and succinic acid were quantified in the cheeses instrumentally. Taste thresholds (best estimate thresholds, BETs) were determined for each compound in water. Subsequently, a trained descriptive sensory analysis panel evaluated each compound in odor-free water across threshold concentrations to confirm that the thresholds were based on umami and not some other stimuli. Model system studies with trained panelists were then conducted with each compound individually or all compounds together. Comparison of analytical data and sensory thresholds indicated that IMP and GMP thresholds were 100-fold higher than their concentrations in cheese. All other compounds contributed some umami taste within their concentration range in umami cheeses. Sensory analysis of model cheeses revealed that glutamic acid played the largest role in umami taste of both Cheddar and Swiss cheeses while succinic and propionic acids contributed to umami taste in Swiss cheeses. Knowledge of the key compounds associated with umami taste in cheeses will aid in the identification of procedures to enhance formation of this taste in cheese.

Validation of a green fluorescent protein-labeled strain of Vibrio vulnificus for use in the evaluation of postharvest strategies for handling of raw oysters.

In this paper we describe a biological indicator which can be used to study the behavior of Vibrio vulnificus, an important molluscan shellfish-associated human pathogen. A V. vulnificus ATCC 27562 derivative that expresses green fluorescent protein (GFP) and kanamycin resistance was constructed using conjugation. Strain validation was performed by comparing the GFP-expressing strain (Vv-GFP) and the wild-type strain (Vv-WT) with respect to growth characteristics, heat tolerance (45 degrees C), freeze-thaw tolerance (-20(o) and -80 degrees C), acid tolerance (pH 5.0, 4.0, and 3.5), cold storage tolerance (5 degrees C), cold adaptation (15 degrees C), and response to starvation. Levels of recovery were evaluated using nonselective medium (tryptic soy agar containing 2% NaCl) with and without sodium pyruvate. The indicator strain was subsequently used to evaluate the survival of V. vulnificus in oysters exposed to organic acids (citric and acetic acids) and various cooling regimens. In most cases, Vv-GFP was comparable to Vv-WT with respect to growth and survival upon exposure to various biological stressors; when differences between the GFP-expressing and parent strains occurred, they usually disappeared when sodium pyruvate was added to media. When V. vulnificus was inoculated into shellstock oysters, the counts dropped 2 log(10) after 11 to 12 days of refrigerated storage, regardless of the way in which the oysters were initially cooled. Steeper population declines after 12 days of refrigerated storage were observed for both iced and refrigerated products than for slowly cooled product and product held under conservative harvest conditions. By the end of the refrigeration storage study (22 days), the counts of Vv-GFP in iced and refrigerated oysters had reached the limit of detection (10(2) CFU/oyster), but slowly cooled oysters and oysters stored under conservative harvest conditions still contained approximately 10(3) and >10(4) CFU V. vulnificus/oyster by day 22, respectively. The Vv-GFP levels in the oyster meat remained stable for up to 24 h when the meat was exposed to acidic conditions at various pH values. Ease of detection and comparability to the wild-type parent make Vv-GFP a good candidate for use in studying the behavior of V. vulnificus upon exposure to sublethal stressors that might be encountered during postharvest handling of molluscan shellfish.

PilP, a pilus biogenesis lipoprotein in Neisseria gonorrhoeae, affects expression of PilQ as a high-molecular-mass multimer.

Studies of gonococcal pilus biogenesis are fundamental to understanding organelle structure/function relationships and identifying new approaches to controlling disease. This area of research is also relevant to elucidating the basic mechanisms of outer membrane translocation of macromolecules, which requires components highly related to those involved in type IV pilus expression. Previous studies have shown that products of several ancillary pil genes are required for organelle biogenesis but of these only PilQ, a member of the GspD protein family, is a component of the outer membrane. DNA sequencing of the region upstream of pilQ revealed the presence of two open reading frames (ORFs) whose deduced polypeptides shared significant identities with proteins required for pilus expression in Pseudomonas aeruginosa and Pseudomonas syringae, the genes for which are arrayed upstream of a gene encoding a PilQ homologue. Gonococcal mutants bearing transposon insertions in these ORFs were non-piliated and failed to express pilus-associated phenotypes, and the corresponding genes were designated PilO and pilP. The piliation defects in the mutants could not be ascribed to polarity on distal pilQ expression as shown by direct measurement of PilQ antigen in those backgrounds and the use of a novel technique to create tandem duplications in the gonococcus (Gc) genome. As predicted by the presence of a consensus lipoprotein signal sequence, PilP expressed in both Escherichia coli and Gc could be labelled with [3H]-palmitic acid. PilP- as well as PilQ- mutants shed PilC, a protein which facilitates pilus assembly and is implicated in epithelial cell adherence, in a soluble form. Combined with the finding that levels of multimerized PiIQ were greatly reduced in PilP- mutants, the results suggest that PilP is required for PilQ function and that PilQ and PilC may interact during the terminal stages of pilus biogenesis. The findings also support the hypothesis that the Gc PilQ multimer corresponds to a physiologically relevant form of the protein required for pilus biogenesis.

The product of the pilQ gene is essential for the biogenesis of type IV pili in Neisseria gonorrhoeae.

The product of the Neisseria gonorrhoeae omc gene possesses regions homologous to those found in members of a protein superfamily that are associated with the translocation of proteins and DNA-protein complexes across the outer membrane. Amongst its protein homologues, Omc has higher overall homology to PilQ, which is required for type IV pilus expression in Pseudomonas aeruginosa, and OrfE, which is required for sequence-specific DNA uptake by Haemophilus influenzae. The function of Omc, however, is unknown and gonococcal omc mutants have not been described. We constructed gonococcal mutants expressing truncated forms of the protein, and found that these mutants are severely defective for both pilus expression and competence for natural transformation. To be consistent with pre-existing pilus gene nomenclature, we have redesignated the gene pilQ instead of omc, and its product, PilQ instead of Omc. The MS11 gene was sequenced and found to differ from the DNA sequence reported for that of another gonococcal strain; these differences were associated with a repeated DNA element, suggesting a genetic basis for structural variation in PilQ. The results also show that PilQ- mutants are distinct from previously described gonococcal pilus-assembly mutants and P. aeruginosa PilQ- mutants by virtue of their expression of rare pilus filaments. Taking these data into account, PilQ is proposed to function in the terminal steps of organelle biogenesis by acting as a pilus channel or pore.

Structural features of fibronectin synthetic peptide FN-C/H II, responsible for cell adhesion, neurite extension, and heparan sulfate binding.

FN-C/H II (KNNQKSEPLIGRKKT), a heparin-binding peptide derived from the COOH-terminal heparin-binding domain of fibronectin, mediates cell adhesion for a variety of cell types and promotes neurite outgrowth. By systematic amino acid substitution of synthetic peptide analogues of FN-C/H II, the basic structural features necessary for activity have been identified in the COOH-terminal residues LIGRKK. This biologically "active" sequence has been located in several other heparin/heparan sulfate-binding proteins and may represent a potential binding motif for sulfated polyanions. NMR structural studies indicate that the COOH-terminal segment of FN-C/H II displays significant multiple-turn or helix-like character suggesting that the RKK sequence may lie on the same surface of the protein, as opposed to alternating in an extended chain motif.

Melanoma cell adhesion and spreading activities of a synthetic 124-residue triple-helical "mini-collagen".

A great variety of cells, such as melanoma cells, fibroblasts, platelets, keratinocytes, and epithelial cells, adhere to and migrate on specific regions within the triple-helical domains of types I, III, and IV collagen. The relative importance of collagen primary, secondary, and tertiary structures on these cellular activities has not been ascertained, as no general synthetic methodology exists to allow for the study of peptides incorporating biologically active sequences in triple-helical conformation. We have thus developed a novel, generally applicable solid-phase branching methodology for the synthesis of aligned, triple-helical collagen-model polypeptides (i.e. "mini-collagens"). Three nascent peptide chains are carboxyl-terminally linked through one N alpha-amino and two N epsilon-amino groups of Lys, while repeating Gly-Pro-Hyp triplets induce triple helicity. A homotrimeric triple-helical polypeptide (THP) of 124 amino acids, incorporating residues 1263-1277 of alpha 1 (IV) collagen, was synthesized. Highly metastatic mouse melanoma cells showed a profound preference for adhesion to this THP as compared with a single-stranded peptide (SSP) incorporating the same type IV collagen sequence or a branched peptide containing eight repeats of Gly-Pro-Hyp (designated GPP*). Specifically, 50% cell adhesion occurred at a THP concentration of 1.12 microM, while comparable levels of adhesion required [SSP] = 170 microM or [GPP*] > 100 microM. Melanoma cells also spread on the THP to a greater extent than on the SSP or GPP*. These results are the first direct demonstrations of the significance of triple helicity for cell adhesion to and spreading on a specific collagen sequence and support earlier conclusions of conformational dependency for cell adhesion to and migration on types I and IV collagen. In addition, the melanoma cell THP activities support the concept that tumor cell adhesion and spreading on type IV collagen involves multiple, distinct domains in triple-helical conformation. The triple-helical peptide synthetic protocol developed here will allow eventually for the study of both structure and biological activity of specific, glycosylated collagen sequences in homotrimeric and heterotrimeric forms.

A cell-surface heparan sulfate proteoglycan mediates neural cell adhesion and spreading on a defined sequence from the C-terminal cell and heparin binding domain of fibronectin, FN-C/H II.

FN-C/H II is a heparin binding synthetic peptide from the C-terminal cell and heparin binding domain of fibronectin (FN) that mediates neuronal cell adhesion, spreading, and neurite outgrowth. Cellular interactions with FN-C/H II are inhibited by soluble heparin, suggesting that a cell-surface proteoglycan may mediate interactions with FN-C/H II (Haugen et al., 1990). To test this hypothesis further, heparan sulfate (HS) or chondroitin sulfate (CS) was removed from the cell surface by enzyme treatment. Heparitinase but not chondroitinase treatment of cells inhibited rat B104 neuroblastoma cell adhesion and spreading on FN-C/H II. Additionally, heparitinase treatment decreased the spreading of cells on the 33/66 kDa fragments containing the C-terminal heparin binding domain of FN. Furthermore, antibodies generated against a mouse melanoma HS proteoglycan (HSPG) inhibited B104 cell adhesion to FN-C/H II and the 33/66 kDa FN fragments. 35S-HSPG isolated from B104 cells directly bound to FN-C/H II both in solid phase assays and by affinity chromatography, but failed to bind to a control peptide from this region, CS1. The binding of 35S-HSPG was predominantly mediated by the HS and not the core protein of the HSPG. SDS-PAGE of iodinated HSPG demonstrated a single 78 kDa core protein following heparitinase digestion, which migrated at 51 kDa under nonreducing conditions. Anti-HSPG antibodies recognized the 78 kDa core protein by immunoblotting, and stained the surface of rat B104 neuroblastoma cells and cells of the primary neonatal rat nervous system. These results identify a cell-surface HSPG that likely mediates neuronal cell binding interactions with FN-C/H II.

Cell surface phosphatidylinositol-anchored heparan sulfate proteoglycan initiates mouse melanoma cell adhesion to a fibronectin-derived, heparin-binding synthetic peptide.

Cell surface heparan sulfate proteoglycan (HSPG) from metastatic mouse melanoma cells initiates cell adhesion to the synthetic peptide FN-C/H II, a heparin-binding peptide from the 33-kD A chain-derived fragment of fibronectin. Mouse melanoma cell adhesion to FN-C/H II was sensitive to soluble heparin and pretreatment of mouse melanoma cells with heparitinase. In contrast, cell adhesion to the fibronectin synthetic peptide CS1 is mediated through an alpha 4 beta 1 integrin and was resistant to heparin or heparitinase treatment. Mouse melanoma cell HSPG was metabolically labeled with [35S]sulfate and extracted with detergent. After HPLC-DEAE purification, 35S-HSPG eluted from a dissociative CL-4B column with a Kav approximately 0.45, while 35S-heparan sulfate (HS) chains eluted with a Kav approximately 0.62. The HSPG contained a major 63-kD core protein after heparitinase digestion. Polyclonal antibodies generated against HSPG purified from mouse melanoma cells grown in vivo also identified a 63-kD core protein. This HSPG is an integral plasma membrane component by virtue of its binding to Octyl Sepharose affinity columns and that anti-HSPG antibody staining exhibited a cell surface localization. The HSPG is anchored to the cell surface through phosphatidylinositol (PI) linkages, as evidenced in part by the ability of PI-specific phospholipase C to eliminate binding of the detergent-extracted HSPG to Octyl Sepharose. Furthermore, the mouse melanoma HSPG core protein could be metabolically labeled with 3H-ethanolamine. The involvement of mouse melanoma cell surface HSPG in cell adhesion to fibronectin was also demonstrated by the ability of anti-HSPG antibodies and anti-HSPG IgG Fab monomers to inhibit mouse melanoma cell adhesion to FN-C/H II. 35S-HSPG and 35S-HS bind to FN-C/H II affinity columns and require 0.25 M NaCl for elution. However, heparitinase-treated 125I-labeled HSPG failed to bind FN-C/H II, suggesting that HS, and not HSPG core protein, binds FN-C/H II. These data support the hypothesis that a phosphatidylinositol-anchored HSPG on mouse melanoma cells (MPIHP-63) initiates recognition to FN-C/H II, and implicate PI-associated signal transduction pathways in mediating melanoma cell adhesion to this defined ligand.

Comparison of serum CA 19-9 and CEA levels in a population at high risk for colorectal cancer.

The sera of 563 patients who underwent colonoscopy were assayed for glycolipid antigen CA 19-9 and CEA. These patients represented a broad spectrum of clinical diseases ranging from advanced metastatic cancer of the colon, pancreas, or stomach to those with negative colonoscopic examination. Sensitivity and specificity for CA 19-9 and CEA were calculated using the following clinical definitions. Malignant or pre-malignant disease was defined as colon, pancreatic or stomach carcinoma, stomach dysplasia, atypical adenomatous polyp, atypical villous adenoma, carcinoma in situ and carcinoma in an adenomatous polyp. When the normal group included patients with adenomatous polyp, hyperplastic adenoma, inflammatory disease and patients with no disease apparent, the sensitivity and specificity for CA 19-9 was 23% and 96%, and for CEA, 23% and 95%, respectively. When adenomatous polyp patients were placed in the malignant or pre-malignant disease group, the sensitivity and specificity for CA 19-9 was 8% and 96%, and for CEA, 11% and 95%, respectively. When comparing CA 19-9 and CEA in colorectal carcinoma, the percent positivity of the CEA assay was equal to, or better than, CA 19-9 in all Dukes' stages. In pancreatic carcinomas CA 19-9 showed better diagnostic performance than CEA.