Dairy Products and Health: Recent Insights

Milk, cheese, yogurt, and other dairy products have long been known to provide good nutrition. Major healthful contributors to the diets of many people include the protein, minerals, vitamins, and fatty acids present in milk. Recent studies have shown that consumption of dairy products appears to be beneficial in muscle building, lowering blood pressure and low-density lipoprotein cholesterol, and preventing tooth decay, diabetes, cancer, and obesity. Additional benefits might be provided by organic milk and by probiotic microorganisms using milk products as a vehicle. New research on dairy products and nutrition will improve our understanding of the connections between these products, the bioactive compounds in them, and their effects on the human body.

Mandatory labels, taxes and market forces: An empirical evaluation of fat policies

The public-health community views mandatory Front-of-Pack (FOP) nutrition labels and nutritional taxes as promising tools to control the growth of food-related chronic diseases. This paper uses household scanner data to propose an ex-ante evaluation and comparison of these two policy options for the fromage blanc and dessert yogurt market. In most markets, labelling is voluntary and firms display fat labels only on the FOP of low-fat products to target consumers who do not want to eat fat. We here separately identify consumer preferences for fat and for FOP fat labels by exploiting an exogenous difference in legal labelling requirements between these two product categories. Estimates of demand curves are combined with a supply model of oligopolistic price competition to simulate policies. We find that a feasible ad valorem fat tax dominates a mandatory FOP-label policy from an economic perspective, but both are equally effective in reducing average fat purchases.

Cross-cultural acceptance of a traditional yoghurt-like product made from fermented cereal

BACKGROUND

Akpan is a traditional ready-to-drink fermented yoghurt-like cereal beverage consumed in urban and rural areas in Benin. With the aim of adapting the product to new local and export markets, this work maps African and European consumer preferences for different types of Akpan.

RESULTS

A sensory profile of Akpan was created and consumer tests were conducted with 103 consumers of African origin and 74 consumers of European origin. Consumer acceptance was significantly correlated with fermented odour (r = -0.94) and milky taste (r = 0.92-0.97) attributes. Cluster analysis revealed different behaviour by African and European consumers with respect to acceptability of Akpan; European consumers did not like the sour taste and African consumers liked an intense sweet milky taste.

CONCLUSION

This study provides information on how Akpan, and other fermented yoghurt-type cereal products, could be adapted to African and European consumer preferences.

Synthesis of novel haptens and development of an enzyme-linked immunosorbent assay for quantification of histamine in foods

Novel haptens were designed and synthesized to prepare antibodies against free histamine, but none resulted in producing suitable antibodies for developing an enzyme-linked immunosorbent assay (ELISA). However, an antiserum was obtained having high specificity and affinity to p-nitrobenzoylated histamine (NPHA), which can be easily formed from reaction between histamine and p-nitrobenzoic acid N-hydroxysuccinimide ester (PNBA-OSu) under mild conditions. Based on rabbit polyclonal antibodies, a competitive indirect ELISA (ciELISA) for histamine determination in foods was developed. After ciELISA and derivatization optimization, the assay showed good sensitivity, with limits of detection of 1.8 mg/kg, 93.6 μg/L, and 93.6 μg/kg in fish, red wine, and yoghurt, respectively, with negligible cross-reactivity with related biogenic amines and amino acids. Average recovery of histamine in fortified food samples ranged from 80.9% to 110.1% with coefficients of variation below 16.3%. Good correlation between the ciELISA and liquid chromatography-tandem mass spectrometry was obtained for spiked food samples.

Antioxidant activity and protein-polyphenol interactions in a pomegranate (Punica granatum L.) yogurt

Pomegranate juice (PGJ) is rich in phenolics which are potent antioxidants but also prone to interact with proteins. A yogurt rich in PGJ (40%) made from arils was elaborated (PGY) to determine the antioxidant activity and to estimate the phenolics-proteins interaction during 28 days of cold storage. Juice, yogurts, and protein-free permeates were analyzed for phenolic composition. Yogurt fermentation modified the anthocyanin profile of the initial PGJ, especially the content in cyanidin-3-O-glucoside. During storage, individual anthocyanin content in PGY decreased but it did not modify yogurt color. The analysis of permeates revealed that the degree of phenol-protein interaction depends on the type of phenolic, ellagic acid and dephinidin-3,5-O-diglucoside being the least bound phenolic compounds. The presence of PGJ in yogurt enhanced radical scavenging performance, whereas all the observed ferric reducing power ability of PGY was strictly due to the PGJ present. The 84.73% of total anthocyanins remained bound to proteins at the first day of storage and 90.06% after 28 days of cold storage, revealing the high affinity of anthocyanins for milk proteins.

Characterization of recombinant Zea mays transglutaminase expressed in Pichia pastoris and its impact on full and non-fat yoghurts

BACKGROUND

Transglutaminases catalyze post-translational modification of proteins by ε-(γ-glutamyl) links and covalent amide bonds. Research on properties and applications of plant transglutaminases is less developed than in animals and micro-organisms. In a previous study, optimized Zea mays transglutaminase was purified from recombinant Pichia pastoris strain. The main objective of the present study was to characterize this enzyme and assess its effect on the properties of yoghurt.

RESULTS

The purified recombinant transglutaminase presented a Km of 3.98 µmol L(-1) and a Vmax of 2711 min(-1) by the fluorometric method. The enzyme was stable after incubation for 30 min below 50 °C and over a broad pH range of 5-8 at -20 °C for 12 h. The results showed that the crosslinking reaction catalyzed by this enzyme could effectively improve the properties of full and non-fat yoghurts. Also, the properties of non-fat yoghurt could be improved similar to the full-fat product by recombinant transglutaminase.

CONCLUSION

The application of recombinant transglutaminase in yoghurt indicated that this enzyme could be used as a substitute for microbial transglutaminase in the production of yoghurt, thus providing experimental evidence for the future application of plant transglutaminases in the food industry.

Investigation of the presence of β-hydroxy-β-methylbutyric acid and α-hydroxyisocaproic acid in bovine whole milk and fermented dairy products by a validated liquid chromatography-mass spectrometry method

A simple, rugged, quantitative, and confirmatory method based on liquid chromatography-mass spectrometry was developed and comprehensively validated for the analysis of the leucine metabolites β-hydroxy-β-methylbutyric acid (HMB) and α-hydroxyisocaproic acid (HICA) in bovine whole milk and yogurt. Mean accuracy (90-110% for HMB and 85-115% for HICA) and total precision (<10% RSD in most cases, except for <20% RSD for HMB at the limit of quantitation) at four concentration levels across three validation runs have been determined. Limits of quantitation for HMB and HICA in whole milk were 20 and 5 μg/L, respectively. Measured concentrations of HMB and HICA were <20-29 and 32-37 μg/L, respectively, in bovine whole milk and <5 and 3.0-15.2 mg/L, respectively, in yogurt. These concentrations are insufficient by large margins to deliver any musculoskeletal benefits, and fortification of milk and dairy products with HMB and/or HICA appears to be justified.

Reduction of the off-flavor volatile generated by the yogurt starter culture including Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in soymilk

Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus establish a symbiotic relationship in milk; however, S. thermophilus predominantly grows in soymilk. This study determined that excess diacetyl was notably generated mainly by S. thermophilus in soymilk, and this flavor compound created an unpleasant odor in fermented soymilk. The addition of l-valine to soymilk reduced the amount of diacetyl and increased the levels of acetoin during fermentation by S. thermophilus . In addition, it was found that the expression of the ilvC gene was repressed and that of the als and aldB genes was stimulated in S. thermophilus by l-valine. Sensory evaluations with the triangle difference test and a preference test showed that the soymilk fermented with l-valine was significantly preferred compared with that without l-valine. In this study, we successfully controlled the metabolic flux of S. thermophilus in soymilk and produced more favorable fermented soymilk without the use of genetically modified lactic acid bacteria strains.

Consumption of yogurts fortified in vitamin D and calcium reduces serum parathyroid hormone and markers of bone resorption: a double-blind randomized controlled trial in institutionalized elderly women

CONTEXT

Nutritional prevention of bone deterioration with fortified foods seems particularly suitable in institutionalized elderly women at risk of vitamin D deficiency, secondary hyperparathyroidism, increased bone resorption, and osteoporotic fracture.

OBJECTIVE

The objective was to evaluate whether fortification of yogurts with vitamin D and calcium exerts an additional lowering effect on serum PTH and bone resorption markers as compared with isocaloric and isoprotein dairy products in elderly women.

DESIGN

A randomized double-blind controlled-trial, 56-day intervention was conducted in institutionalized women (mean age 85.5 years) consuming 2 125-g servings of either vitamin D- and calcium-fortified yogurt (FY) at supplemental levels of 10 μg/d vitamin D₃ and 800 mg/d calcium or nonfortified control yogurt (CY) providing 280 mg/d calcium.

MAIN OUTCOMES

The endpoints were serum changes from baseline (day 0) to day 28 and day 56 in 25-hydroxyvitamin-D (25OHD), PTH, and bone resorption markers tartrate-resistant acid phosphatase isoform-5b (TRAP5b), the primary outcome, and carboxyl-terminal cross-linked telopeptide of type I collagen (CTX).

RESULTS

At day 56, serum 25OHD increased (mean ± SEM) by 25.3 ± 1.8 vs 5.2 ± 2.5 nmol/L in FY (n = 29) and CY (n = 27), respectively (P < .0001). The corresponding changes in PTH were -28.6% ± 7.2% vs -8.0% ± 4.3% (P = .0003); in TRAP5b, -21.9% ± 4.3% vs 3.0% ± 3.2% (P < .0001); and in CTX, -11.0% ± 9.7% vs -3.0% ± 4.1% (P = .0146), in FY and CY, respectively. At day 28, these differences were less pronounced but already significant for 25OHD, PTH, and TRAP5b.

CONCLUSIONS

This study in institutionalized elderly at high risk for osteoporotic fracture suggests that fortification of dairy products with vitamin D₃ and calcium provides a greater prevention of accelerated bone resorption as compared with nonfortified equivalent foods.

Caffeine increases liking and consumption of novel-flavored yogurt

RATIONALE

Caffeine has been shown to increase preference for beverages with which it is paired; however, it is not known if caffeine alters liking for foods with which it is paired indirectly.

OBJECTIVES

The purpose of the current experiment was to test the hypothesis that a caffeinated beverage paired with a novel-flavored yogurt will increase preference for that yogurt compared to one paired with placebo. We also tested the hypothesis that liking would increase more when caffeine was paired with high energy density yogurt.

METHODS

Men and women (n = 62) were randomized to receive a beverage containing placebo (PLA) or caffeine (CAF) and to consume a low (LED) or high energy density (HED), novel-flavored yogurt. Participants rated, ranked, and consumed seven novel-flavored yogurts and then had a target yogurt paired with either PLA or CAF over four consecutive days.

RESULTS

In general, yogurt liking increased over time, the HED yogurt was liked more than the LED yogurt, and yogurt paired with caffeine was liked more than yogurt paired with placebo. Participants showed a significant increase in liking of LED yogurt paired with caffeine compared to those with LED yogurt paired with placebo.

CONCLUSIONS

Caffeine administration may increase liking and consumption of novel-flavored foods, particularly if the food is not highly liked at baseline. This suggests that caffeine pairing may be a way to increase liking of LED foods, such as vegetables and fruit.

Impact of fruit piece structure in yogurts on the dynamics of aroma release and sensory perception

The aim of this work was to gain insight into the effect of food formulation on aroma release and perception, both of which playing an important role in food appreciation. The quality and quantity of retronasal aroma released during food consumption affect the exposure time of olfactory receptors to aroma stimuli, which can influence nutritional and hedonic characteristics, as well as consumption behaviors. In yogurts, fruit preparation formulation can be a key factor to modulate aroma stimulation. In this context, the impact of size and hardness of fruit pieces in fat-free pear yogurts was studied. Proton Transfer Reaction-Mass Spectrometry (PTR-MS) was used to allow sensitive and on-line monitoring of volatile odorous compound release in the breath during consumption. In parallel, a trained panel used sensory profile and Temporal Dominance of Sensations (TDS) methods to characterize yogurt sensory properties and their dynamic changes during consumption. Results showed that the size of pear pieces had few effects on aroma release and perception of yogurts, whereas fruit hardness significantly influenced them. Despite the fact that yogurts presented short and similar residence times in the mouth, this study showed that fruit preparation could be an interesting formulation factor to enhance exposure time to stimuli and thus modify food consumption behaviors. These results could be taken into account to formulate new products that integrate both nutritional and sensory criteria.

Determination of antioxidant activity in foods and beverages by reaction with 2,2'-diphenyl-1-picrylhydrazyl (DPPH): collaborative study First Action 2012.04

A colorimetric method for the determination of total antioxidant activity in a variety of foods and beverages was validated in both a single-laboratory validation and a collaborative laboratory validation study. The procedure involved extraction of the antioxidants directly into a methanol-water solution containing a known amount of 2,2'-diphenyl-1-picrylhydrazyl (DPPH), thus promoting the rapid reaction of extracted materials with DPPH. The reaction was monitored by spectrophotometric measurement of the absorbance loss at 517 nm. Antioxidant activity was quantified relative to a dilution series of vitamin E analog standards (Trolox), which were analyzed in parallel simultaneously with the food and beverage samples. The antioxidant activities of the samples ranged from 131 to 131 000 micromole Trolox equivalents/100 g. Statistical analysis of the results showed that nine of the 11 matrixes gave acceptable HorRat values, indicating that the method performed well in these cases. The acceptable matrixes include pomegranate juice, blueberry juice, carrot juice, green tea, wine, rosemary spice, ready-to-eat cereal, and yogurt. Two samples failed the HorRat test: the first was an almond milk that had an antioxidant level below the practical LOQ for the method; the second was a sample of canola oil with added omega-3 fatty acid that was immiscible in the reaction medium.

Organic and conventional nonflavored yogurts from the Italian market: study on sensory profiles and consumer acceptability

BACKGROUND

The sensory properties of food products are an important success factor, especially in the organic market, where many producers and distributors of organic food claim superior taste for their products compared to the conventional alternative. For this reason consumer expectations and preferences, as well as the sensory properties of conventional and organic yogurt, have to be investigated in depth. In this work, the sensory profiling and consumer data of six nonflavored organic and conventional Italian yogurts were elaborated. Some results on the data segmentation (heavy and light users of organic food) and on the effect of information on liking (blind and labeled test) were obtained. Multivariate analysis was carried out to study how the sensory characteristics of 'natural yogurts' drive consumer liking.

RESULTS

Consumers' preferences were oriented towards a creamy mouthfeel and smooth visual appearance and for a less acid and fresh taste. In particular, a conventional yogurt was the least accepted, because it was not creamy enough. This paper shows there is room to improve unflavored yogurt to better meet consumer expectations.

CONCLUSION

Sensory profiling did not allow a distinction in odor/taste/texture between organic and conventional samples. However, three of four organic samples were in the region of highest consumer acceptability, fitting well consumers' preference. There was no clear tendency that heavy or light users scored differently in the blind and labeled tests regarding overall liking but, for all, the most liked conventional yogurt scored higher when labeled as organic.

Colour evaluation of a phycobiliprotein-rich extract obtained from Nostoc PCC9205 in acidic solutions and yogurt

BACKGROUND

Phycobiliproteins are coloured proteins produced by cyanobacteria, which have several applications because of their colour properties. However, there is no available information about the colour stability of phycobiliproteins from Nostoc sp. in food systems. The aim of this work was to study the colour stability of a purple-coloured phycobiliprotein-rich extract from the cyanobacterium Nostoc PCC9205 in acidic solutions and yogurt.

RESULTS

Variations of pH for Nostoc PCC9205 extract have shown stability for the L* (lightness) and a* (redness) indexes in the range 1.0-7.0. The b* index (blueness), however, increased at pH values below 4.0, indicating loss of the blue colour. The Nostoc PCC9205 extract was used as colorant in yogurt (pH 4.17) stored for 60 days. Instrumental colour analysis showed no changes for the L* and a* indexes during storage, whereas the b* index changed after 20 days of storage. A multiple comparison test showed colour instability after 20 days of storage. A hedonic scale test performed on the 60th day of storage showed acceptability of the product.

CONCLUSIONS

The red component of the phycobiliprotein-rich extract from Nostoc PCC9205 presented an improved stability in acidic media and yogurt compared with the blue component of this extract.

Food matrix effects on in vitro digestion of microencapsulated tuna oil powder

Tuna oil, containing 53 mg of eicosapentaenoic acid (EPA) and 241 mg of docosahexaenoic acid (DHA) per gram of oil, delivered as a neat microencapsulated tuna oil powder (25% oil loading) or in food matrices (orange juice, yogurt, or cereal bar) fortified with microencapsulated tuna oil powder was digested in simulated gastric fluid or sequentially in simulated gastric fluid and simulated intestinal fluid. The level of fortification was equivalent to 1 g of tuna oil per recommended serving size (i.e., per 200 g of orange juice or yogurt or 60 g of cereal bar). The changes in particle size of oil droplets during digestion were influenced by the method of delivery of the microencapsulated tuna oil powder. Lipolysis in simulated gastric fluid was low, with only 4.4-6.1% EPA and ≤1.5% DHA released after digestion (as a % of total fatty acids present). After sequential exposure to simulated gastric and intestinal fluids, much higher extents of lipolysis of both glycerol-bound EPA and DHA were obtained (73.2-78.6% for the neat powder, fortified orange juice, and yogurt; 60.3-64.0% for the fortified cereal bar). This research demonstrates that the choice of food matrix may influence the lipolysis of microencapsulated tuna oil.

Chitosan interaction with iron from yoghurt using an in vitro digestive model: comparative study with plant dietary fibers

The objective of this work was to investigate the interaction of chitosan with iron from yoghurt by an in vitro gastrointestinal tract model. Taking into account that chitosan is a polysaccharide included in fiber definition by Codex Alimentarius; chitosan behavior was studied and compared with different plant fiber (wheat, bamboo, apple, psyllium and inulin) behaviors, in the same in vitro conditions. Ferrous sulfate was added to yoghurts with each type of fiber. The gastric environment was simulated with HCl (pH 1.0-2.0). The duodenal environment was simulated with NaHCO(3) (pH 6.8-7.2) and a dialysis tubing cellulose membrane. Results showed that chitosan had the highest iron retention percentages (53.2% at 30 min; 56.8% at 60 min) interacting in a more pronounced manner with iron than the plant fibers used in this work.

GC-based analysis of plant stanyl fatty acid esters in enriched foods

Approaches for the capillary gas chromatographic (GC) based analysis of intact plant stanyl esters in enriched foods were developed. Reference compounds were synthesized by enzyme-catalyzed transesterifications. Their identities were confirmed by means of mass spectrometry. Using a medium polar trifluoropropylmethyl polysiloxane stationary phase, long-chain plant stanyl esters could be separated according to their stanol moieties and their fatty acid chains. Thermal degradation during GC analysis was compensated by determining response factors; calibrations were performed for ten individual plant stanyl esters. For the analysis of low-fat products (skimmed milk drinking yogurts), the GC separation was combined with a "fast extraction" under acidic conditions. For fat-based foods (margarines), online coupled LC-GC offered an elegant and efficient way to avoid time-consuming sample preparation steps. The robust and rapid methods allow conclusions on both, the stanol profiles and the fatty acid moieties, and thus provide a basis for the authentication of this type of functional food ingredients.

[Acceptance of yoghurt with different functional ingredients among consumers in supermarkets in southern Chile]

In view of the interest in the role of foodstuffs in improving wellbeing and health, the object of this study is to distinguish consumer typologies in Temuco, La Araucanía Region, Chile, according to their preferences for different functional ingredients, flavouring, colouring and price in yoghurt. A semi-structured survey was applied to 400 supermarket customers. The respondents ordered eight alternative yoghurts according to their preferences, with different functional ingredients (fibre, antioxidants), flavourings (sugar, sweetener), colouring (natural, artificial) and three price options, for a conjoint analysis with fractional factorial design. Variables affecting knowledge of "functional food" were evaluated using a binomial logit model. It was determined by conjoint analysis that in general a preference existed for yoghurt containing fibre, sweetener, natural colouring, and at the lowest price. Three typologies were distinguished by analysis of hierarchical conglomerates: the majority segment (48.8%) displayed a greater preference for fibre; the second (41.7%) also preferred fibre, but gave first priority to artificial colouring and preferred a higher price. The minority (9.5%) was the only segment to prefer antioxidants. The typologies differed significantly in satisfaction with their food-related life, knowledge of the function of fibre and presence of cancer and obesity in some member of the respondent's family. The binomial logit model was significant (P < 0.01), indicating that if the consumer has a job or has had access to information on functional foods, the probability increased of knowledge of what these mean. There was thus majority acceptance of yoghurt enriched with fibre and with added sweetener.

Effects of 1.23% acidulated phosphate fluoride gel and drinkable yogurt on human enamel erosion, in vitro

OBJECTIVES

In this in vitro study, the authors sought to determine the effects of 1.23% acidulated phosphate fluoride gel (APF) or drinkable yogurt on human enamel after exposure to an acidic drink.

METHOD AND MATERIALS

Sixteen surgically removed, caries-free, human third molars were cut into four portions: mesial, distal, buccal, and lingual. Each portion was distributed into one of four groups, with each specimen embedded in acrylic resin and its enamel center lightly ground and polished. Three groups of specimens were immersed in orange juice for 2 minutes. One group received no other treatment (OR), one group was subsequently immersed in drinkable yogurt for 5 minutes (OR:YO), while another group had 1.23% APF applied for 4 minutes (OR:APF). The final group was immersed in only drinkable yogurt for 5 minutes (YO). Each exposure was performed twice daily for 60 days; between exposures, the samples were stored in artificial saliva. The enamel surfaces were monitored by three criteria: erosion depth, surface hardness, and SEM.

RESULTS

Erosion depth increased progressively in all groups. Surface microhardness progressively decreased in all groups except the OR:APF group, where hardness was significantly higher than other groups at 60 days (P < .05). SEM inspection revealed preferential loss of rod crystallites with retention of interrod crystallites in all specimens exposed to orange juice. The enamel exposed to only drinkable yogurt revealed modest and uniform etching.

CONCLUSION

Drinkable yogurt alone or posttreatment of enamel after exposure to an acidic drink with either 1.23% APF or drinkable yogurt leads to enamel dissolution and does not reduce enamel erosion, in vitro.

Nutritional and sensory quality of stirred soursop (Annona muricataL.) yoghurt

Soursops (Annona muricata L.) are highly aromatic fruits with white juicy flesh and are native to tropical North and South America. The ripe fruits are highly perishable, as they become soft and easily bruised. The objectives of the study were to incorporate soursop nectar at 0%, 5%, 10% and 15% in stirred yoghurts and to analyse the products for chemical and sensory quality. A focus group evaluated the initial yoghurts for process modifications. Yoghurts were evaluated on sensory attributes of appearance and colour, body and texture, flavour and aroma, and overall quality. Yoghurts with 10% and 15% soursop nectar had the highest (P<0.05) overall quality scores (12.60/20 and 12.75/20, respectively) but differed (P<0.05) in flavour and aroma from plain yoghurt and 5% soursop yoghurt. Most panelists would consider purchase of 10% and 15% soursop yoghurts over 0% and 5% soursop yoghurts. These yoghurts provided high percentage daily values of zinc, phosphorus and calcium and a good level of protein.

Study on β-galactosidase enzymatic activity of herbal yogurt

Different types of herbal yogurts were developed by mixing standardized milk with pretreated herbs, namely tulsi leaf (Ocimum sanctum), pudina leaf (Mentha arvensis) and coriander leaf (Coriandrum sativum), with leaves separately and a 1:1 (v/v) mixture of the strains of lactic starter cultures---Lactobacillus acidophilus (NCIM 2903) and Lactobacillus plantarum (NCIM 2083)-followed by incubation at 40 degrees C for 6 h. The beta-galactosidase enzymatic activity of the abovementioned herbal yogurts was determined and interestingly noted to exhibit higher enzymatic activity compared with the control yogurt (without any herbs). Among all herbal yogurts, tulsi yogurt had the maximum beta-galactosidase activity.