溶菌酶及其在食品工业中的应用

溶菌酶是一种对人安全且具有保健作用的蛋白酶,是国际公认的绿色天然酶制剂。它在食品工业中被广泛用作食品添加剂和防腐剂。溶菌酶广泛存在于人、动植物及微生物体内,尤以鸡蛋清中含量较高,具有巨大的开发应用价值。     

Lysozyme as a barrier to growth of Bacillus anthracis strain Sterne in liquid egg white, milk and beef

In this study, we investigated the role of lysozyme on the viability of Bacillus cereus, Bacillus subtilis, Bacillus pumilus and Bacillus anthracis (Sterne) in egg white (EW), ground beef and milk. At 35 °C in EW, growth rates (GR) for B. cereus, B. subtilis, B. pumilus and B. anthracis were 0.005, −0.018, −0.028 and −0.029 OD₆₀₀/h, respectively. Heat-treating EW at 55 and 60 °C reduced the inactivating effect of EW by 3.1 and 10.5-fold, respectively. Addition of lysozyme (2 mg/ml) to 60 °C-treated EW increased the inactivation rate 5.76-fold, indicating involvement of lysozyme in B. anthracis inactivation. B. anthracis inactivation was influenced by pH, as shown by a progressive increase in inactivation rate from 0.25 to −4.42 logs CFU/h over a pH range of 6.0-8.5. Adding 2 mg/ml lysozyme to milk and ground beef also suppressed the growth of B. anthracis 3.3 and 6.5-fold, respectively. These data indicate that lysozyme, as a natural component of EW or potential additive in other foods, could reduce biothreat risks presented by bioterror agents.     

Preferred information strategies for food allergic consumers. A study in Germany, Greece, and The Netherlands

Information provided on food packaging is currently the most important method enabling food allergic consumers to eliminate allergens from their diet. This study aimed to identify the preferences of food allergic consumers regarding different information provision scenarios. Respondents (N = 287) filled out a web-based questionnaire on their preferences regarding a food label, an in-store booklet, and an ICT-solution. ICT methods will not replace effective food labelling, but may be used to supplement information provided by labels. Recommendations for information delivery to food allergic patients in the form of labels and booklets, as well as personalised (novel ICT) approaches, are provided.     

Methods to evaluate egg freshness in research and industry: A review

The modern poultry industry is not satisfied with the traditional system of the handling and processing of eggs which is based on candling and visual inspection of the eggs. Currently, the operator of the conveyer does not have the opportunity to inspect 120 000 eggs per hour and to estimate the freshness, weight, bacterial infection, presence of technical spoilage, eggshell defects without elimination of subjectivity, fatigability and destruction. That is why the problem of automatization of egg quality control is rather difficult. In order to assure a high and consistent egg quality, an attractive and alternative strategy for determining the state of egg freshness can be achieved by sensors technologies. These techniques (e.g., near-infrared, mid-infrared, fluorescence spectroscopies, etc.) appear to be very promising for non-destructively determining egg freshness because they are relatively not expensive. Such methods cannot eliminate the need for more detailed physico-chemical analyses, but they may help to screen samples that require further examination.     

Comparative resistance of food proteins to adult and infant in vitro digestion models

IgE‐mediated allergy to milk and egg is widespread in industrialised countries and mainly affects infants and young children. It may be connected to an incomplete digestion of dietary proteins causing an inappropriate immune response in the gut. In order to study this, a biochemical model of infant gastroduodenal digestion has been developed, which has reduced levels of protease (eightfold for pepsin and tenfold for trypsin and chymotrypsin), phosphatidylcholine and bile salts, compared with the adult model. This model has been used to study the behaviour of three characterised food‐relevant proteins (bovine β‐lactoglobulin (β‐Lg), β‐casein (β‐CN) and hen's egg ovalbumin), all of which are relevant cows' milk and hens' egg allergens. Digestion products were characterised using electrophoresis, immunochemical techniques and MS. These showed that ovalbumin and β‐CN were digested more slowly using the infant model compared with the adult conditions. Resistant fragments of β‐CN were found in the infant model, which correspond to previously identified IgE epitopes. Surprisingly, β‐Lg was more extensively degraded in the infant model compared with the adult one. This difference was attributed to the tenfold reduction in phosphatidylcholine concentration in the infant model limiting the protective effect of this phospholipid on β‐Lg digestion.     

Target groups for organic wine: The importance of segmentation analysis

In light of low and stagnating market shares of organic wine, there is an ongoing debate about growth potential for organic wine. A recent study revealed that even consumers of organic food did not necessarily purchase organic wine regularly. The aim of this contribution was to analyse the wine preferences of organic food consumers and identify promising new target groups for organic wine. We conducted choice experiments in Germany (N = 600) and analysed the data with mixed logit models and latent class models, revealing interesting differences between the results of the two approaches. While the mixed logit models suggested ‘organic’ was the most important wine attribute, the latent class models challenged this proposition. While three of four consumer segments had a strong preference for organic, only one segment in the red wine model (and no segment in the white wine model) gave organic highest priority. Just like non-organic consumers, many organic food consumers seem to use price or country of origin as the most important quality cue for wine. The comparison between the results of the choice experiments and the participants’ stated normal purchase behaviour suggested there is growth potential for organic wine. Apparently, consumers of organic food would buy more organic wine if their preferred type and variety of conventional wine would be available in organic quality at similar price levels.     

Detection of hen’s egg white lysozyme in food: Comparison between a sensitive HPLC and a commercial ELISA method

Recently some cases described allergic reactions to undeclared lysozyme present in foods. In order to protect the allergic consumer, a better control is needed based on reliable and specific detection and quantification methods. The two currently used methods, a commercially available enzyme-linked immunosorbent assay (ELISA) for egg white allergens and a liquid chromatographic method, were compared. Despite the technical specifications of the ELISA kit, ensuring quantitative analysis of lysozyme in absence of other egg white proteins, no reliable quantitative and even qualitative data could be obtained which contrasted with the capabilities of the instrumental technique. A more elaborated evaluation of the methods on spiked samples identified the causes of the observed discrepancies. It was shown that next to a poor sensitivity of the ELISA kit also an insufficient lysozyme extraction and a co-extraction of interfering substances were the causes of the anomalies observed during application of the immunochemical method.     

The wine headache: Consumer perceptions of sulfites and willingness to pay for non-sulfited wines

A panel of 223 alcohol consumers recruited in a liquor store participated in a survey/best–worst experiment investigating perceptions on sulfites and willingness to pay for non-sulfited wines. We find that 34% of our sample experiences headaches after consuming moderate amounts of wine, and sulfites are the most frequently attributed cause. Based on a rank ordered logit estimation of best–worst choices, headache syndrome sufferers are willing to pay a ceteris paribus premium of $1.23 per bottle to avoid added sulfites. However, results from a (logit) model of purchase intentions suggest that quality and price are most important, with differentiating labels (no sulfite added, organic) playing only a marginal role. Marketing implications for the wine industry are offered, and negative perceptions toward sulfites are contextualized within the hypothesis of a “lightning rod” effect induced by the “contains sulfites” warning label.     

The narcissistic wine consumer: How social attractiveness associated with wine prompts narcissists to engage in wine consumption

Wine consumption can help improve one’s social image. Given this social aspect of wine, we predict that because individuals who are high in narcissism strive for social admiration, wine represents a product of choice for them. In Study 1 (N = 654), we show that for narcissistic people, wine is associated with greater social attractiveness, which in turn leads to higher consumption of wine. We also draw a typology of narcissistic wine consumers. In Study 2 (N = 192), we replicate the mediation results of Study 1 and take a step further by examining the influence of anticipated emotional value. More specifically, we show that the sequence above whereby narcissistic people consume higher amounts of wine due to its social attractiveness not only holds, but is stronger when the emotional value that such people anticipate from wine consumption is low. In other words, narcissists engage more in wine consumption for social reasons when they do not (versus do) anticipate wine consumption as a pleasurable experience. We provide a discussion of the practical implications of our results for wine producers and policymakers.     

A simple method for total quantification of mannoprotein content in real wine samples

Mannoproteins released by yeast cells throughout the winemaking process contribute in several ways to improve wine quality. For this reason, some winemaking practices have been developed in order to increase the mannoprotein content of wine. However, monitoring of mannoprotein content of wine during these processes, or even mannoprotein quantification in the final wines, is an analytical problem not easily solved so far. Here, we report a simple and accurate method for mannoprotein quantification in wines. The method involves isolation of wine polysaccharides by size exclusion chromatography, acid hydrolysis, elimination of acid by weak anionic exchange solid phase extraction, and analysis of monosaccharides by ion exclusion HPLC. Advantages over previously existing methods include low sample volumes, possibility of parallel processing for multiple samples, absence of precipitation steps, and clear distinction between mannoproteins and other wine polysaccharides.     

IgE-binding and in vitro gastrointestinal digestibility of egg allergens in the presence of polysaccharides

This work studies the IgE-binding and in vitro gastrointestinal digestibility of the main egg allergens, ovalbumin (OVA) and ovomucoid (OM), in the presence of pectin (P), gum arabic (G) and xylan (X), functional biopolymers commonly used in the food industry. To this aim, solutions of OVA or OM and P, G or X were digested by using a model that mimics physiological conditions. Gastric and duodenal digests were analysed by SDS-PAGE, RP-HPLC and SEC and the specific human-IgE binding capacity was assessed by immunoblotting and ELISA using sera from egg-sensitized patients. The reactivity towards human IgE of OVA and OM was considerably increased in the presence of the polysaccharides and their susceptibility to digestion was diminished when compared with the isolated proteins. As a result, the duodenal digests obtained in the presence of polysaccharides retained more IgE-binding than the isolated protein digests. Overall, the present results underline the importance of the food matrix in the digestibility of food allergens and in their potential to trigger an immune response.     

Bioactive compounds in wine: Resveratrol,hydroxytyrosol and melatonin: A review

Regular moderate wine consumption is often associated with reduced morbidity and mortality from a variety of chronic diseases in which inflammation is the root cause. This review is focused on three of the numerous bioactive compounds present in wine: resveratrol, hydroxytyrosol and melatonin. Resveratrol and hydroxytyrosol are polyphenols. Melatonin, recently described in wine, is an indoleamine. Their structures, concentrations in wine, bioavailability, pharmacokinetic and health promoting properties are reviewed. Resveratrol seems to be one of the most promising compounds due to its bioactivity, with wine being the main source of resveratrol in diet. Hydroxytyrosol, which its main source in diet is olive oil has been also found in both red and white wine in considerable amounts. Melatonin has been found in wine in low amounts. However, both high bioactivity and bioavailability have been attributed to it. They show antioxidant, cardioprotective, anticancer, antidiabetic, neuroprotective and antiaging activities. However, human studies are still in the initial stages and therefore further studies are needed.     

A new methodology to determine cell wall mannoprotein content and release in wine yeasts

Representing around 40% of the cell wall dry weight, mannoproteins are complex macromolecules structurally composed of polymers of sugar, 98% being mannose, covalently linked to peptides. Along the last two decades, these compounds have gained ground as very relevant molecules in the field of winemaking, mainly due to their positive contributions in the development of appreciated organoleptic features and to their contribution in the chemical stabilization of wine. Several methodologies have been recently proposed to achieve the quantification of these compounds. However, these methodologies are laborious, time consuming and do not allow a global quantification of these macromolecules. In this paper, an easy, reliable and fast forward methodology for the quantification of mannoproteins in model must is proposed and evaluated. Its application in the quantification of mannoproteins content in yeast cell wall is also demonstrated.     

Comparison between capillary electrophoresis and HPLC-FL for ochratoxin A quantification in wine

A capillary electrophoresis method with DAD detection has been developed and validated for ochratoxin A (OTA) determination in wine and compared with a previously validated HPLC-FL method. Although the use of UV detection has originated a high value for the quantification limit and, therefore, this method can not be used yet in the determination of OTA in wine in real samples, the analytical performance of the CE-DAD method is fully satisfactory. The more important advantage of CE is the use of the economical and ecological aqueous borate buffer in the separation process. A good correlation of the results has been obtained when 27 fortified wine samples were analyzed by CE-DAD and HPLC-FL. This work demonstrates that the CE technique is a valuable alternative to HPLC-FL analysis of OTA in wine if fluorescence detection is available.     

Extrinsic attributes responsible for red wine quality perception: A cross-cultural study between France and Spain

Understanding quality perception requires focusing both on product proprieties and consumers’ representations. The goal of this study was to access the representations of perceived extrinsic wine quality of consumers from two different wine regions in two European countries with an important wine tradition: La Rioja-RJ-(Spain) and Côtes du Rhône-CdR-(France).Twenty commercial red wines (ten from RJ and ten from CdR) were evaluated in terms of quality by means of a categorization task. Ninety-five French and 93 Spanish consumers had to categorize the 20 wines according to four levels of quality going from very low to very high quality.Three clusters of French and two of Spanish consumers have been identified. Country-of-origin of wine arises as the most important extrinsic cue for less-involved French and Spanish consumers, while more-involved consumers with higher knowledge in wine are able to interpret and use a wider range of cues. Consumers’ knowledge, involvement and nationality appear to be good predictors of quality perception.These results are relevant for the field of sensory analysis in that they help understanding the construction of quality perception. The wine industry can benefit also from these results, especially when exporting wines. This cross-cultural study may help them to develop marketing strategies able to enhance the quality perception of wines and to make use of different extrinsic factors.     

Comparison of different extraction solutions for the analysis of allergens in hen’s egg

An important requirement for the correct procedure of allergen analysis in hen’s egg is to obtain complete and unaltered protein extracts. Besides the aim of a quantitative extraction of the allergens from the matrix, it is equally important not to alter their allergenic potential during the extraction process. This paper describes and compares six extraction solutions for the analysis of whole-egg proteins and allergens. These requirements were examined via protein determination according to Bradford [Bradford, M. M. (1976). Rapid and sensitive method for quantitation of microgram quantities of protein utilizing principle of protein–dye binding. Analytical Biochemistry, 72, 248–254] and Kjeldahl [Meyer, A. H. (2006). Lebensmittelrecht, Verlag C.H. Beck München, Stand: 1. February 2006, § 64, Lebensmittel- und Futtermittelgesetzbuch, Amtliche Sammlung von Untersuchungsmethoden, Nr. L 06.00-7] as well as the EAST-inhibition method. It could be demonstrated that the extraction with a urea solution (8 M) led to significant interferences during the protein determination, and substantially reduced the allergenic potential of egg proteins. With all other extraction solutions adequate protein contents could be extracted. The highest protein content was achieved by the extraction with phosphate buffered saline followed by a Tween 20 solution, physiological saline, water, and acetate buffer. The results show that none of these extracts – except for the urea solution (8 M) – was altered in its’ allergenic potential.     

Role of lees in wine production: A review

The sometimes contradictory role attributed by scientists to lees in wine production is discussed in this review. Studies dealing with the importance of lees in the natural removal of undesirable compounds from wine, the effect of lees–wine contact on the volatile fraction of wines, the key influence of lees on biogenic amine contents in wines, the interactions between lees and phenolic compounds, and the importance of mannoproteins and lipids released by lees have been critically reviewed. Finally, the present exploitation of lees is also outlined.