VOLATILE FLAVOR COMPOUNDS AFFECTING CONSUMER ACCEPTABILITY OF KIWIFRUIT

Sensory research on kiwifruit has shown that specific sugars and acids, and volatile flavor compounds have causative effects on "sweet" and "acid" aroma and flavor attributes. New Zealand consumers (n = 162) assessed the perceived flavor intensity and acceptability of three volatile flavor compounds (ethyl butanoate, E-2-hexenal and hexanal) at varying levels in a model base solution. Increasing levels of ethyl butanoate positively affected all the acceptability attributes ("overall liking,""liking of aroma,""liking of flavor") as well as increased the perceived intensity of "kiwifruit aroma" and "kiwifruit flavor." Increasing levels of E-2-hexenal negatively affected all the acceptability attributes but increased the perceived intensity of "kiwifruit aroma" and "acid flavor." An increase in hexanal increased perceived intensity of "kiwifruit aroma." Ethyl butanoate and E-2-hexenel at the levels tested had the most prominent effects on consumer perceived intensity and acceptability of the "kiwifruit flavor."     

PERCEPTION OF FAT IN A MILK MODEL SYSTEM USING MULTIDIMENSIONAL SCALING

This study examined the contributions of stimulus fat content and flavor volatiles to the perception of fat in a milk model system. The model system was formulated by adding bland vegetable oil (0%, 5%, or 10% w/v) and natural cream flavor (0%, 0.5% or 1% w/v) to a skim milk base. Panelists judged pairs of samples for similarity on the basis of three attributes (fat content, mouthcoating and thickness) and the results were analyzed using a multidimensional scaling procedure. Two-dimensional solutions best represented the data. The stimulus spaces for fat content and mouthcoating were visually similar to each other and provided reasonable separation of the samples. Instrumental measures helped to define the underlying dimensions of the stimulus space for fat content. Dimension 1 related to texture and included the contributions of viscosity, and fat particle size and number distribution; dimension 2 related to flavor perception. The sample with a moderate fat content (5%) and the highest concentration of added cream flavor (1%) was perceived to be similar to the 10% fat samples with added flavor. Thus, the added flavor provided the sensation of higher fat content. These data suggest that flavor plays an important role in the preception of fat in dairy foods. A psychophysical model of fat perception in dairy foods is proposed which includes the contribution of viscosity, fat particle size and number distribution, and volatile flavor perceptions.     

Perceptual interactions between characteristic notes smelled above aqueous solutions of odorant mixtures

Twenty-two experienced panelists rated odor intensity of aqueous solutions of citral, octen-1-ol-3, and hexanal. The panel assessed unmixed components and mixtures (9 binary and 4 ternary). In sensory sessions dedicated to mixtures (n = 6), evaluation was focused on one target odor, presented at a fixed concentration. All components had lower odor intensity on mixed presentations. In many cases, information obtained from simpler systems was not extended to complex mixtures. In a mixture, the competition between odorant molecules on qualitative aspects (dominance/suppression) imbalanced components contribution, anticipated from the quantitative distribution. Hexanal appeared to be the potentially weaker odorant in paired combinations, whereas octen-1-ol-3 had a lower relative impact on ternary systems. Suppression of the odor of octen-1-ol-3 and a concomitant increase in the odor of hexanal was common to all ternary mixtures. Reciprocal inhibition of octen-1-ol-3 and citral odors through perceptual interactions was suspected. Mutual suppression is suspected to have eased the perception of hexanal intensity.     

THE POTENTIAL OF CERTAIN FUNGI AS SOURCES FOR NATURAL FLAVOR COMPOUNDS

Bacteria have been used for years as flavor compound sources.However, little attention has been given to fungal sources forsuch compounds. This brief review was not intended to coverall aspects of flavor compound formation from all types of fungiand food systems. However, representative data are presentedto demonstrate that a wide variety of compounds possessing uniqueand potent flavor properties have been isolated as naturallyoccurring constituents of fungi.     

INFLUENCE OF FOOD MATRIX STRUCTURE AND ORAL BREAKDOWN DURING MASTICATION ON TEMPORAL PERCEPTION OF FLAVOR

Perception of flavor intensity from a series of model foods was recorded during normal mastication by 8 subjects. Samples varied in gelatin concentration (5–25%) and in the sweetener added (sucrose or aspartame) and represented a range of physical and mechanical properties. All contained the same level of a commercial flavor (banana). Mastication patterns were recorded using electromyography simultaneously with sensory assessment. Increasing the mechanical strength and melting point of the samples resulted in longer chewing times and lower intensity and more prolonged flavor perception. The temporal pattern of flavor perception was closely linked with mastication patterns for each subject but exhibited large individual differences. Flavor perception was influenced by the habitual oral breakdown patterns for individuals.     

The influence of sodium salts on binary mixtures of bitter-tasting compounds

In order to study potential mixture interactions among bitter compounds, selected sodium salts were added to five compounds presented either alone or as binary bitter-compound mixtures. Each compound was tested at a concentration that elicited 'weak' perceived bitterness. The bitter compounds were mixed at these concentrations to form a subset of possible binary mixtures. For comparison, the concentration of each solitary compound was doubled to measure bitterness inhibition at the higher intensity level elicited by the mixtures. The following sodium salts were tested for bitterness inhibition: 100 mM sodium chloride (salty), 100 mM sodium gluconate (salty), 100 and 20 mM monosodium glutamate (umami), and 50 mM adenosine monophosphate disodium salt (umami). Sucrose (sweet) was also employed as a bitterness suppressor. The sodium salts differentially suppressed the bitterness of compounds and their binary combinations. Although most bitter compounds were suppressed, the bitterness of tetralone was not suppressed, nor was the bitterness of the binary mixtures that contained it. In general, the percent suppression of binary mixtures of compounds was predicted by the average percent suppression of its two components. Within the constraints of the present study, the bitterness of mixtures was suppressed by sodium salts and sucrose independently, with few bitter interactions. This is consistent with observations that the bitter taste system integrates the bitterness of multi-compound solutions linearly.     

Effects of sample handling temperatures on bovine skim milk progesterone concentrations

The effects of incubation of whole milk at various temperatures and times on the concentration of progesterone in the skim milk fraction was determined. For the study, milk samples were collected from 10 pregnant Holstein cows. The milk from each cow was transferred to culture tubes to provide 32 replicates of 3 ml volume. To begin the incubation study, all samples were placed in a 37 degrees C water bath for 4 h. The end of this incubation was designated as time 0 and a sample from each cow was centrifuged to harvest skim milk. At time 0, samples from each cow were divided among incubation temperatures of 0 degrees, 4 degrees, 20 degrees and 37 degrees C. Samples were removed from each incubation group at 30, 60, 90 and 120 min. After 120 min, all remaining samples were returned to the 37 degrees C incubation and skim milk was collected at 30, 60 and 90 min. Progesterone was measured in skim milk by radioimmunoassay. The mean +/- SE concentration of progesterone in skim milk at time 0 was 10.9 +/- 1.1 nmol/L. The mean concentration of progesterone in skim milk was higher (P < 0.05) in all samples incubated at 0 degrees and 4 degrees C, with incremental increases ranging from 34% to 67% above time 0. Progesterone in skim milk returned to time 0 concentrations in milk samples transferred from 0 degrees or 4 degrees C to 37 degrees C. There was no change in skim milk progesterone in whole milk samples incubated at 20 degrees or 37 degrees C. From this study, it can be concluded that the concentration of progesterone in skim milk is temperature dependent. Inconsistency in handling whole milk samples can have a profound effect in the concentration of progesterone on skim milk. The temperature-dependent effect was reversible and may be related to solubility of progesterone in milk fat.     

植物乳杆菌ST-Ⅲ发酵特性的研究

在添加5%(v/v)番茄汁的改良配方乳中对植物乳杆菌ST-Ⅲ单菌或与嗜热链球菌及保加利亚乳杆菌混合发酵的生长特性、发酵乳风味进行了研究.结果表明,在脱脂乳中添加5%(v/v)番茄汁可以明显缩短植物乳杆菌ST-Ⅲ单菌发酵时的凝乳时间,提高其活菌数.在改良的配方乳中,三菌混合发酵制备的发酵乳具有良好的酸奶风味、无涩味.但与...     

TEXTURE-FLAVOR INTERACTIONS IN LOW FAT STIRRED YOGURT: HOW MECHANICAL TREATMENT, THICKENER CONCENTRATION AND AROMA CONCENTRATION AFFECT PERCEIVED TEXTURE AND FLAVOR

The influence of thickening agent (0 and 7g/L), mechanical treatment (low and high) and flavoring agent concentration (2.2 to 63.2 μL/kg) on texture, taste and aroma of low fat stirred yogurts was investigated through sensory profiling by a panel of ten subjects trained on 13 attributes. Two assessment conditions were used: either in the presence or in the absence of olfactory perception (nostrils closed with nose clips). Sensory differences were greater for texture than for the other perception modalities. Olfactory perception enhanced yogurt astringency. If both thickener addition and mechanical treatment influenced texture attributes and rheology, the second factor had the strongest effect. Texture attributes were highly correlated with rheological parameters. Increasing flavoring agent concentration tended to decrease thickness and the addition of thickening agent depressed green apple notes and sweet taste, suggesting texture/flavor interactions.     

RELEASE OF ARTIFICIAL CHERRY FLAVOR FROM ICE CREAMS VARYING IN FAT AND FAT REPLACERS

The effect of fat and fat replacers (FR) on the flavor release from cherry ice cream was investigated. Protein based FR, Simplesse ("S") and carbohydrate based FR, Litesse ("L") either partially or completely substituted milk fat in ice cream. Overall and temporal flavor profiles of ice cream during eating were obtained using chemical and sensory analyses. The performance of FR depended on the level of fat it was substituting and the amount of fat present in the ice cream. In the reduced fat ice cream group, both FRs failed to mimic the characteristics of 6% fat ice cream, mainly because of the low retention of cherry flavor. In the full fat ice cream group, the sensory properties of ice cream containing "L" were closer to the full-fat (12%) ice cream than those with "S". The critical flavor volatile compounds that strongly impact the sensory flavor attributes were identified.     

Assessing the efficacy of candidate mosquito repellents against the background of an attractive source that mimics a human host

Mosquito repellents are used around the globe to protect against nuisance biting and disease‐transmitting mosquitoes. Recently, there has been renewed interest in the development of repellents as tools to control the transmission of mosquito‐borne diseases. We present a new bioassay for the accurate assessment of candidate repellent compounds, using a synthetic odour that mimics the odour blend released by human skin. Using DEET (N,N‐diethyl‐meta‐toluamide) and PMD (p‐menthane‐3,8‐diol) as reference compounds, nine candidate repellents were tested, of which five showed significant repellency to the malaria mosquito Anopheles gambiae sensu stricto (Diptera: Culicidae). These included: 2‐nonanone; 6‐methyl‐5‐hepten‐2‐one; linalool; δ‐decalactone, and δ‐undecalactone. The lactones were also tested on the yellow fever mosquito Aedes aegypti (Stegomyia aegypti) (Diptera: Culicidae), against which they showed similar degrees of repellency. We conclude that the lactones are highly promising repellents, particularly because these compounds are pleasant‐smelling, natural products that are also present in human food sources.     

RELATING SENSORY AND CHEMICAL DATA TO UNDERSTAND FLAVOR

Flavor cannot be measured directly by instruments, it is an interaction of consumer and product. A gas chromatogram, even with 250 peaks on it, does not say anything about the flavor, only about the volatiles. In some cases a character impact compound might be present, in a second group of products a small number of compounds may be responsible for the majority of the flavor, while a third class contains more complex foods, which have generally been processed in some way. A range of methods has been, more or less, successfully used to try to link composition data to flavor data, including the calculation of odor units, fractionation of chromatographic effluent, “nasal appraisal” of chromatographic effluent, and a range of multivariate statistical procedures. However, defects in understanding of the mechanism of operation of the chemical senses has limited the success which has been achieved.     

EFFECTIVENESS OF CATEGORY AND LINE SCALES TO CHARACTERIZE CONSUMER PERCEPTION OF FRUITY FERMENTED FLAVOR IN PEANUTS

Fruity fermented (FF) flavor is a common off‐flavor in peanuts resulting from high‐temperature curing. The 9‐point hedonic scale is the most widely used scale to determine consumer acceptance; however, research has indicated that line scales may provide equal reliability and greater sensitivity. The objectives of this study were to characterize consumer perception of FF flavor in peanuts and to compare the effectiveness of the two scale types. Consumers (n = 208) evaluated control (no FF), low‐intensity (1.0) FF and high‐intensity (3.0) FF peanut pastes for the strength/intensity of roasted peanut flavor (RPF), sweet taste (ST), fresh peanut flavor (FPF) and overall liking (OV) using randomly assigned ballots. Sensitivity in defining consumer perception of off‐flavor in peanuts was greater with use of line scales than with the hedonic scale. The line scale indicated that FF flavor in peanuts, even at low intensity, negatively impacted OV and further identified significantly lower RPF and FPF perception by consumers. The hedonic scale identified only a difference in FPF and was not sensitive enough to show a difference in OV.     

Plasma membrane fragments in bovine and caprine skim milks

By either differential or linear gradient ultracentrifugation of bovine or caprine skim milks it was possible to obtain fractions which contained 45–75% of the lipid phosphorus and unesterified cholesterol of the skim milk. Electron microscopy of these fractions revealed the presence of numerous membrane-bound vesicles, microvilli and membrane fragments. Assay of the fractions for certain membrane-bound enzymes; i.e. 5′-nucleotide pyrophosphatase, alkaline phosphatase and ATPases, established the presence of all but the latter in the membrane-rich fractions. The distributions of the enzymes in the various fractions were correlated with their lipid phosphorus and cholesterol contents.Compositions of the phospholipids from skim milk membranes, milk fat globule membranes and the plasma membrane of the lactating mammary cell were observed to be similar and unique for having a relatively high level (20–25%) of sphingomyelin. By virtue of secretory processes, all of these membranes appear to be interrelated with each other and with Golgi vesicle membranes. It is concluded that the membrane material in the skim milk originates primarily from plasma membrane of the lactating cell. The possibiltiy that Golgi vesicle membranes form a substantial part of this material is not precluded by the results of this study.Separation of bovine skim milk on a Sepharose 4B gel column demonstrated that virtually all of the 5′-nucleotidase and lipid phosphorus are recovered together in the void volume of the column. Considering the particle size discriminating characteristics of this gel, the skim milk membrane material appears to be constituted of relatively large structures rather than of discrete subunits.     

Diacetyl control during brewery fermentation via adaptive laboratory engineering of the lager yeast <Emphasis Type="Italic">Saccharomyces pastorianus</Emphasis>

Diacetyl contributes to the flavor profile of many fermented products. Its typical buttery flavor is considered as an off flavor in lager-style beers, and its removal has a major impact on time and energy expenditure in breweries. Here, we investigated the possibility of lowering beer diacetyl levels through evolutionary engineering of lager yeast for altered synthesis of α-acetolactate, the precursor of diacetyl. Cells were exposed repeatedly to a sub-lethal level of chlorsulfuron, which inhibits the acetohydroxy acid synthase responsible for α-acetolactate production. Initial screening of 7 adapted isolates showed a lower level of diacetyl during wort fermentation and no apparent negative influence on fermentation rate or alcohol yield. Pilot-scale fermentation was carried out with one isolate and results confirmed the positive effect of chlorsulfuron adaptation. Diacetyl levels were over 60% lower at the end of primary fermentation relative to the non-adapted lager yeast and no significant change in fermentation performance or volatile flavor profile was observed due to the adaptation. Whole-genome sequencing revealed a non-synonymous SNP in the ILV2 gene of the adapted isolate. This mutation is known to confer general tolerance to sulfonylurea compounds, and is the most likely cause of the improved tolerance. Adaptive laboratory evolution appears to be a natural, simple and cost-effective strategy for diacetyl control in brewing.