Comparing quality and emotional responses as related to acceptability of light-induced oxidation flavor in milk

A Hydrotalcite-Based PET Composites with Enhanced Properties for Liquid Milk Packaging Applications

In the present work, the two-phase mixture (HTLc) of hydrotalcite and its oxide were used to improve the barrier properties, UV resistance and antimicrobial activity of Poly(ethylene terephthalate) (PET) for their application in liquid milk packaging. Firstly, CaZnAl-CO₃-LDHs with a two-dimensional layered structure were synthesized by hydrothermal method. CaZnAl-CO₃-LDHs precursors were characterized by XRD, TEM, ICP and dynamic light scattering. A series of PET/HTLc composite films were then prepared, characterized by XRD, FTIR and SEM, and a possible mechanism of the composite films with hydrotalcite was proposed. Barrier properties to water vapor and oxygen have been studied in PET nanocomposites, as well as their antibacterial efficacy by the colony technique and their mechanical properties after exposure to UV irradiation for 24 h. By the presence of 1.5 wt% HTLc in the PET composite film, the oxygen transmission rate (OTR) was reduced by 95.27%, the water vapor transmission rate was reduced by 72.58% and the inhibition against Staphylococcus aureus and Escherichia coli was 83.19% and 52.75%. Moreover, a simulation of the migration process in dairy products was used to prove the relative safety. This research first proposes a safe technique for fabricating hydrotalcite-based polymer composites with a high gas barrier, UV resistance and effective antibacterial activity.

Emotional responses to taste and smell stimuli: Self-reports, physiological measures, and a potential role for individual and genetic factors

Taste and olfaction elicit conscious feelings by direct connection with the neural circuits of emotions that affects physiological responses in the body (e.g., heart rate and skin conductance). While sensory attributes are strong determinants of food liking, other factors such as emotional reactions to foods may be better predictors of consumer choices even for products that are equally-liked. Thus, important insights can be gained for understanding the full spectrum of emotional reactions to foods that inform the activities of product developers and marketers, eating psychologist and nutritionists, and policy makers. Today, self-reported questionnaires and physiological measures are the most common tools applied to study variations in emotional perception. The present review discusses these methodological approaches, underlining their different strengths and weaknesses. We also discuss a small, emerging literature suggesting that individual differences and genetic variations in taste and smell perception, like the genetic ability to perceive the bitter compound PROP, may also play a role in emotional reactions to aromas and foods.

Effect of Purple Corn Anthocyanin on Antioxidant Activity, Volatile Compound and Sensory Property in Milk During Storage and Light Prevention

The aim of this study was to observe the effect of purple corn anthocyanin on the light-induced antioxidant activity, free radicals, volatile compounds, color parameters, and sensory properties of milk during storage. There were four groups: (1) negative control, no addition of anthocyanins + exposure to fluorescent light (NC); (2) positive control 1, no addition of anthocyanins + protected from fluorescent light (PC1); (3) positive control 2, the addition of 0.3% (w/v) anthocyanins + exposure to fluorescent light (PC2); and (4) the addition of 0.3% anthocyanins + protected from fluorescent light (AC). The results indicated that the concentration of antioxidant activity parameters in the NC group decreased during the entire storage period, whereas antioxidant activity parameters were unchanged except for the glutathione peroxidase (GSH-Px) in the AC group. Moreover, the NC group showed lower levels of 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and higher levels of superoxide anion and hydrogen peroxide than the other groups after 1 d of storage period. The extent of malondialdehyde accumulation and lipid peroxidation in the control groups were greater than that of the AC group. Twenty-two volatile compounds were determined in milk, which consisted of eight alcohols, three ketones, five aldehydes, two esters, and four hydrocarbons by headspace gas chromatography mass spectrometer analysis. Specifically, individual aldehydes, esters and hydrocarbons in the AC group remained at relatively stable values during storage relative to the other three groups. Stronger positive correlations were detected between several antioxidant activities (superoxide dismutase, GSH-Px) and DPPH scavenging activity as well as total ketones in milk. Adding of anthocyanin did not impact on the color values of L^*, a^* and b^* in light-protected milk during the entire storage period. Some sensory evaluation parameters (flat, garlic/onion/weedy, oxidized-light, oxidized-metal, rancid) in AC group were significantly higher than that of the control group at the end of the period. In conclusion, the current study revealed that the addition of purple corn anthocyanin pigment to light-protected milk had the potential to prevent lipid oxidation, enhance antioxidant activity, maintain volatile compounds and increase the sensory scores.

Use of auctions to assess consumer value for milk from different packaging

The objective of this study was to evaluate the effect of a sensory experience and educational message on consumer value for fluid milk in different containers: translucent high-density polyethylene (HDPE), white-pigmented HDPE (light-block), and paperboard. We carried out 11 auction sessions (n = 100). Sessions included an explanation of the experiment process; a survey about demographics and milk purchasing and consumption behaviors; a sensory evaluation; an educational message; and 3 rounds of nth price auctions. Consumers were blindly served 2 pairs of milk samples-2% milk from paperboard and translucent HDPE, and skim milk from paperboard and translucent HDPE-and asked to indicate their preference and level of acceptability for each, using a 7-point hedonic scale. Consumers were asked to ascribe a monetary value to each sample. Consumers were also asked to taste and assess a value for 2% and skim milk from light-block HDPE. All milk samples were evaluated simultaneously by a panel of 9 judges who were trained to evaluate milk quality attributes on a 15 cm unstructured line scale. All milk was from the same industry source, processed and stored on the same timeline for each session. Results from the consumer panel on acceptability, trained panel descriptive analysis and consumer bids were analyzed using multi-factor ANOVA. Subjecting responses to pre- and post-surveys to k means cluster analysis revealed 4 bidding populations in each round. Trained panelists detected higher levels of light-oxidized off-flavor in skim milk from translucent HDPE (5.8 cm) than from light-block HDPE (2.42 cm) and in 2% milk from translucent HDPE (5.1 cm) than from paperboard (0.32 cm). Although 84% of participants regularly purchased milk in plastic containers, consumers' acceptability scores for milk of the same fat content but from different packaging were not different. However, consumers gave higher acceptability scores to 2% milk from paperboard (5.2/7.0) than skim milk from paperboard (4.7/7.0). We found no differences in consumer value (US$) for 2% or skim milk in paperboard or translucent HDPE. However, after consumers received an educational message and tasted "Certified Fresh Taste" samples, they were willing to pay more for 2% milk in paperboard ($0.31 more) or HDPE ($0.38 more) packaging with a "Certified Fresh Taste" seal and for skim milk in paperboard ($0.15 more) or HDPE ($0.21 more) packaging with a "Certified Fresh Taste" seal than for milk in packaging without such labeling. Although consumers could not detect a difference in the milk from different packages, they indicated that they would pay more for a "Certified Fresh Taste" seal after hearing about the effects of light on milk in different packaging, demonstrating the importance to consumers of external cues about freshness.

The State of Automated Facial Expression Analysis (AFEA) in Evaluating Consumer Packaged Beverages

In the late 1970s, analysis of facial expressions to unveil emotional states began to grow and flourish along with new technologies and software advances. Researchers have always been able to document what consumers do, but understanding how consumers feel at a specific moment in time is an important part of the product development puzzle. Because of this, biometric testing methods have been used in numerous studies, as researchers have worked to develop a more comprehensive understanding of consumers. Despite the many articles on automated facial expression analysis (AFEA), literature is limited in regard to food and beverage studies. There are no standards to guide researchers in setting up materials, processing data, or conducting a study, and there are few, if any, compilations of the studies that have been performed to determine whether any methodologies work better than others or what trends have been found. Through a systematic Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) review, 38 articles were found that were relevant to the research goals. The authors identified AFEA study methods that have worked and those that have not been as successful and noted any trends of particular importance. Key takeaways include a listing of commercial AFEA software, experimental methods used within the PRISMA analysis, and a comprehensive explanation of the critical methods and practices of the studies analyzed. Key information was analyzed and compared to determine effects on the study outcomes. Through analyzing the various studies, suggestions and guidance for conducting and analyzing data from AFEA experiments are discussed.

Does vitamin fortification affect light oxidation in fluid skim milk?

Off-flavors in milk related to light oxidation form due to photoxidation of native riboflavin and tetrapyrroles, resulting in an array of lipid oxidation compounds. Recent work has established that fortification with water-dispersible vitamin A can result in off-flavors in fluid skim milk caused by vitamin A degradation products in the vitamin premix. The objective of this study was to determine the role of vitamin fortification on light oxidation of high temperature, short time pasteurized fluid skim milk. First, the aroma profiles and aroma-active volatile compounds in light-exposed vitamin premixes were determined by exposing the premixes to fluorescent (FL) or light-emitting diode (LED) light at 2,000 lx at 4°C for 0, 2, 4, 8, or 24 h. A trained panel (n = 6) documented aroma profiles of each vitamin premix at each time point. Headspace solid-phase microextraction followed by gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS) were performed to characterize aroma-active compounds in light-exposed vitamin premixes. In the second experiment, commercial vitamin premixes (vitamin A and vitamin D in oil and water matrices) were used to fortify skim milk (vitamin A: 3,000 IU/946 mL; vitamin D: 600 IU/946 mL). Skim milk was pasteurized, homogenized, and packaged in 946-mL high-density polyethylene jugs. Milks were exposed to FL or LED light at 2,000 lx at 4°C for 4, 12, 24, or 48 h. Controls with and without vitamins and light shielding were included. Riboflavin and vitamin A and D degradation were quantified via ultra-high-performance liquid chromatography. A trained panel (n = 8) documented sensory profiles of milks at each time point. Lipid oxidation volatile compounds were quantified via solid-phase microextraction with GC-MS. Vitamin degradation volatile compounds were quantified via solvent-assisted sorptive stir bar extraction with GC-MS. Riboflavin, vitamin A, and vitamin D degradation were consistent with that reported in previous studies. We found no effect of vitamin fortification on development of typical light oxidation-related off-flavors (cardboard and mushroom) or lipid oxidation-related volatiles (hexanal and heptanal). A perfumey/floral flavor was documented in the oil-based vitamin A-fortified milk, suggesting that light exposure affected the off-flavors contributed by water- versus oil-based vitamin fortification. These results show no evidence that vitamin fortification at current levels provides any protection against light oxidation-related off-flavors in fluid milk.

Efficacy of light-protective additive packaging in protecting milk freshness in a retail dairy case with LED lighting at different light intensities

Light emitting diodes (LED) are rapidly developing as dominant lighting systems in dairy retail cases. Bright light is typically chosen to best exhibit milk products. However, high intensity LED lighting may create high potential for detrimental oxidation and destroying milk freshness. In this study, we investigated the interaction between LED light intensity, exposure time, and packaging material on limiting milk oxidation and protecting milk freshness and vitamins. Within 4 h of LED light exposure at an intensity as low as 1068 lx, light-induced oxidation occurred on 2% milkfat milk with commercial packaging including glass and translucent high-density polyethylene (HDPE) bottles. Higher light intensity (>4094 lx) and longer light exposure time (>24 h) rapidly increased the oxidation rate in milk. Polyethylene terephthalate (PET) packaging with lower oxygen permeability rate effectively reduced (P < 0.05) vitamin A degradation under low light intensity within 24 h. A combination of light-protective additive (TiO₂) and oxygen barrier material (PET) successfully reduced (P < .05) the loss of dissolved oxygen and riboflavin, and decreased the formation of final oxidation products in milk, as measured by thiobarbituric reactive substances (TBARS), when exposed to high light intensity within 24 h. Lower LED light intensity in retail case was preferred by 50% of participants in a visual acceptance test; consumers are willing to consider pigmented packaging with limited visibility. Results of this study provides guidance for dairy industry in choosing appropriate LED lighting conditions and packaging to adequately display the milk products as well as minimize the degradation of milk nutrients and flavor.

Effects of Pro-Oxidants and Antioxidants on the Total Antioxidant Capacity and Lipid Oxidation Products of Milk During Refrigerated Storage

Oxidized flavor is a major problem that affects the dairy industry because of its adverse effect on milk acceptability. The objectives of this research were to examine the roles of pro-oxidants and antioxidants on the oxidative stability of whole milk. In the 1st experiment, the effect of light (2300 Lux) and/or cupric sulfate (0, 0.5, and 1.0 mg/kg) as pro-oxidants in milk were investigated during an 11-d refrigerated storage period. The effects of added retinyl palmitate (1.16 mg/L; 2113 IU Vitamin A/L) and tocopheryl acetate (100 mg/kg milk fat; 5.02 IU Vitamin E/L) as antioxidants in the presence of light (2300 Lux) and light with cupric sulfate (0.05 mg/kg) during a 7-d study were investigated in the 2nd experiment. The presence of pro-oxidants significantly (P < 0.05) decreased the total antioxidant capacity (TAC) and increased the lipid oxidation products in milk during storage. Light had a greater effect in the decrease of TAC, although cupric sulfate in the presence of light significantly increased the formation of lipid oxidation products. The addition of antioxidants resulted in a significant (P < 0.05) increase in TAC on day 0. However, with exposure to light and light with cupric sulfate, the antioxidants did not result in a higher TAC in comparison to the treatments without added antioxidant. Analysis of lipid oxidation products by instrumental and sensory methods showed that the presence of light and cupric sulfate significantly (P < 0.05) increased the oxidized flavor from the control, but no significant (P > 0.05) difference in oxidized flavor intensity was detected between milk with and without added antioxidants.

PRACTICAL APPLICATION

Production and processing variables can affect the content of pro-oxidants and antioxidants in milk, which has an impact on flavor. An understanding of the role of these components in contributing to or minimizing off-flavor formation in milk, will help dairy producers to provide quality products to consumers.

Development and Application of a Test for Food-Induced Emotions

This study aimed to develop a test to measure food-induced emotions suitable for stable food and beverages. All of the experiments were conducted under the conditions of a consumer sensory evaluation according to German standard DIN 10974. Test development included descriptors’ derivation and factor analysis as well as a comparison between the new test (empathic food test, EFT) and a hedonic sensory test and an unspecific psychological test, known as a multidimensional mood questionnaire (MDMQ). Nineteen sensory experts derived twelve items using free-choice profiling. After an exploratory factor analyses, ten of the intended twelve items were integrated into two scales. To compare the new questionnaire (EFT) to the MDMQ and a hedonic test, panels of 59 (EFT), 64 (MDMQ) and 63 (hedonic sensory test) untrained individuals described their perceptions after consuming sensorially similar pairs of milk, water, bread and sugar. The benchmark of comparison was the power to discriminate between the food pairs. Test-retest replicability was demonstrated. All three tests presented slight differences in sample preference and effect size depending on the offered products. These findings underscore the need to test new methods with a wide range of products. Further research is needed to investigate the relationship between sensorial perception and emotional response.