脱乙酰改性对魔芋葡甘聚糖/黑米膳食纤维复合膜特性的影响

目的 探究脱乙酰对魔芋葡甘聚糖(konjac glucomannan, KGM)/黑米膳食纤维复合膜特性的影响。方法 对KGM进行脱乙酰改性,将脱乙酰前后的KGM与黑米膳食纤维、甘油、蛭石共混,采用流延法制备两种复合膜,以复合膜拉伸强度、断裂伸长率、水蒸气透过率、溶水率为考察因素,确定最优配方,并通过傅里叶变换红外光谱和扫描电镜进行表征。结果 魔芋葡甘聚糖/黑米膳食纤维复合膜制备最佳配方为每100 mL蒸馏水中添加魔芋葡甘聚糖0.37 g、黑米膳食纤维0.074 g、甘油0.60 g、蛭石0.074 g,复合膜的拉伸强度可达11.20 MPa。脱乙酰魔芋葡甘聚糖/黑米膳食纤维复合膜最佳配方为每100 mL蒸馏水中添加脱乙酰度0.2%魔芋葡甘聚糖0.37 g、黑米膳食纤维0.074 g、甘油0.50 g、蛭石0.074 g,在此条件下,拉伸强度为12.67 MPa。脱乙酰改性使复合膜抗拉强度提高13%、断裂伸长率降低17%、溶水率降低12%、水蒸气透过系数降低41%,红外光谱与扫描电镜结果表明脱乙酰魔芋葡甘聚糖黑米膳食纤维复合膜具有更高的稳定性。结论 脱乙酰改性处理改善了复合膜微观结构,...     

How dietary intake has been assessed in African countries? A systematic review

Background: Dietary patterns are often considered as one of the main causes of non-communicable diseases worldwide. It is of utmost importance to study dietary habits in developing countries since this work is scarce.

Objective: To summarize the most recent research conducted in this field in African countries, namely the most used methodologies and tools.

Methods: A systematic review was conducted on MEDLINE®/PubMed, aiming to identify scientific publications focused on studies of dietary intake of different African populations, in a ten-year period. Papers not written in English/Portuguese/Spanish, studies developed among African people but not developed in African countries, studies aiming to assess a particular nutrient/specific food/food toxin and studies that assessed dietary intake among children were excluded.

Findings: Out of 99 included studies, the 24-hour recall and the food-frequency questionnaire were the most used dietary intake assessment tools, used to assess diet at an individual level. It was also observed that often country-unspecific food composition databases are used, and the methodologies employed are poorly validated and standardized.

Conclusions: There is an emergent need to improve the existing food databases by updating food data and to develop suitable country-specific databases for those that do not have their own food composition table.     

无淀粉脱硫魔芋精粉加工技术研究

高纯度低含硫是魔芋原料升级及出口中的关键问题,利用淀粉和魔芋葡甘聚糖在乙醇介质中糊化特性的差异,本文首次采用回流法进行脱淀粉脱硫处理,结果表明:浸提2次,乙醇浓度40%(V/V),pH4.5,料液比1:7,回流时间60min,产品中可以完全去除所有淀粉;选择不同的脱硫方法之间没有显著差异,均可将含硫量降低至50mg/kg以下,回流法在脱除淀粉的同时,可将含硫量降至20mg/kg,可望成为魔芋精制极具前途的方法.     

Histamine food poisonings: A systematic review and meta-analysis

Objective: The aim of this study was to assess the mean of histamine concentration in food poisoning.

Design: Systematic review and meta-analysis of reports published between 1959 and 2013.

Study selection: Main criteria for inclusion of studies were: all report types that present outbreaks of “histamine poisoning' or “scombroid syndrome” from food, including histamine content and type of food. Health status of people involved must be nonpathological.

Results: Fifty-five (55) reports were included, these studies reported 103 incidents. All pooled analyses were based on random effect model; histamine mean concentration in poisoning samples was 1107.21 mg/kg with confidence interval for the meta-mean of 422.62–2900.78 mg/kg; heterogeneity index (I2) was 100% (P < 0.0001); prediction interval was 24.12–50822.78 mg/kg. Fish involved in histamine poisoning was mainly tuna or Istiophoridae species. No clues of association between concomitant conditions (female sex, alcohol consumption, previous medication, and consumption of histamine releasing food) and histamine poisoning, were highlighted.

Conclusions: This is the first systematic review and meta-analysis that analyzes all the available data on histamine poisoning outbreaks evaluating the histamine concentration in food involved. Histamine mean concentration in poisoning samples was fairly high. Our study suffers from some limitations, which are intrinsic of the studies included, for instance the lack of a complete anamnesis of each poisoning episode.

Protocol registration: Methods were specified in advance and have been published as a protocol in PROSPERO database (18/07/2012 -CRD42012002566).     

Healthy Virgin Olive Oil: A Matter of Bitterness

Virgin olive oil (VOO) is the pillar fat of Mediterranean diet. It is made from olive fruits and obtained by squeezing olives without any solvent extraction. Respect to the seed oils, an unique polar polyphenol-rich fraction gives VOO a bitter and pungent taste.

The recent substantiation by European Food Safety Authority (EFSA) of a health claim for VOO polyphenols may represent an efficient stimulus to get the maximum health benefit from one of the most valuable traditional product of Mediterranean countries educating consumers to the relationship between the VOO bitterness and its health effect.

Agronomical practices and new processing technology to avoid phenolic oxidation and hydrolysis and to enhance the aromatic components of the VOO have been developed and they can be used to modulate taste and flavor to diversify the products on the market. VOOs having high concentration of phenol compounds are bitter and pungent therefore many people do not consume them, thus loosing the health benefits related to their intake.

In this paper, the chemist's and nutritionist's point of view has been considered to address possible strategies to overcome the existing gap between the quality perceived by consumer and that established by expert tasters. Educational campaigns emphasizing the bitter-health link for olive oils should be developed.     

A critical review on hepatoprotective effects of bioactive food components

Background: Bioactive food components are nonessential biomolecules, which help to give beneficial effects to human being against several diseases. Natural bioactive food components derived from plants and animals, such as phytosterols, carotenoids, polyphenols and fatty acids, have been proposed as valuable substitutions for anticipation and management of hepatotoxic effects and its chronic complications based on in vitro and in vivo studies.

Objectives of the study: To summarize drugs and chemical-induced hepatotoxicity and review how various bioactive food components attenuate the hepatotoxicity via cellular mechanisms.

Results: Remarkable studies demonstrated that the health promoting effects of bioactive components originated from plants have been frequently attributed to their antioxidant properties and facilitate to increase cellular antioxidant defense system and thereby scavenge free radicals, inhibit lipid peroxidation, augment anti-inflammatory potential, and further protect the liver from damage.

Conclusion: In this critical review, we summarize current progress in clarifying the molecular mechanism in hepatotoxicity and curative potential of the bioactive food components and its successive clinical outcomes in the field of drug discovery and overcome the problems of medication and chemical-induced hepatotoxic effects.     

Toward predictive food process models: A protocol for parameter estimation

Mathematical models, in particular, physics-based models, are essential tools to food product and process design, optimization and control.

The success of mathematical models relies on their predictive capabilities. However, describing physical, chemical and biological changes in food processing requires the values of some, typically unknown, parameters. Therefore, parameter estimation from experimental data is critical to achieving desired model predictive properties.

This work takes a new look into the parameter estimation (or identification) problem in food process modeling. First, we examine common pitfalls such as lack of identifiability and multimodality. Second, we present the theoretical background of a parameter identification protocol intended to deal with those challenges. And, to finish, we illustrate the performance of the proposed protocol with an example related to the thermal processing of packaged foods.     

Determination of diffusion and partition coefficients of model migrants by direct contact and vapour phase transfer from low-density polyethylene films into cake

The aim of the present study was to determine the migration kinetics of one photoinitiator, benzophenone, and two optical brighteners, Uvitex OB and 1,4-diphenyl-1,3-butadiene (DPBD), from low-density polyethylene (LDPE) films into cake. Transfer was assessed by both direct contact and also the vapour phase.

To perform the migration tests by direct contact, plastic films enriched with the additives were placed between two cake slices. To evaluate the migration through the gas phase, cake and the fortified LDPE film were placed with no direct contact in a glass container that was hermetically closed. Samples were stored at different time–temperature conditions.

Target compounds were extracted from the films with ethanol (70°C, 24 h) and analysed by HPLC-DAD. Relevant parameters such as partition and diffusion coefficients between food and plastic film were calculated. The Arrhenius equation was applied to estimate the diffusion coefficient at any temperature.

The data indicate that migration of benzophenone occurs in a significant extent into cake by both direct contact and through the gas phase (no direct contact). Conversely, very little migration occurred for Uvitex OB by direct contact and none through the gas phase. Results for benzophenone suggest that migration through the gas phase should be considered when evaluating migration from food packaging materials into food.     

Nutrition and chemosensory perception in the elderly

The elderly person's perception of foods and food flavor is affected by age‐associated changes in the chemical senses (taste, smell, and trigeminal sensation). Both classic and modern psychophysical techniques have been applied to achieve some understanding of these changes.

Taste threshold sensitivity declines with age; however, the magnitude of the decline and the degree to which taste qualities are differentially affected remains to be understood. Suprathreshold taste intensity perception is affected by age, but there is a differential effect of taste quality.

Experiments with blended foods have indicated that both olfactory and taste deficits contribute to older people's difficulty with food identification. Experiments assessing threshold sensitivity, suprathreshold intensity, and suprathreshold identification have all demonstrated significant impairment in olfaction in old age. In fact, these effects are far greater than in the taste system.

Patients with Alzheimer's disease show even greater olfactory deficits than normal elderly and the effect is related to the degree of dementia. We have ruled out nasal disease in these patients as the primary causes of olfactory insensitivity, because significant impairment remains when the influence of nasal airflow and nasal cytology has been removed statistically. Both normal elderly and patients with Alzheimer's disease show impairment in odor memory. Sensitivity to, familiarity with, and identifiability of the odors all play a role in odor memory performance.

Flavor preference also changes over the lifespan. Older subjects, for instance, rate high concentration of sugar and salt as pleasanter than young subjects do. Multiple influences contribute to this phenomenon. Elderly persons and those of lower nutritional status have shown preferences for higher concentrations of casein hydrolysate than young persons and those of higher nutritional status, suggesting that dietary preference can be related to chemosensory cues.

There are significant age‐associated changes in chemosensory perception that have the potential to interact with dietary selection and nutrition in the elderly. A better understanding of these phenomena may promote health and well‐being in the elderly.     

Dietary fiber,inulin, and oligofructose: A review comparing their physiological effects

Dietary fiber is a general terra. It covers a wide variety of substances that belong to the family of carbohydrates that resist hydrolysis by human alimentary enzymes but are fermented by colonie microflora.

The main physiological effects of dietary fiber are primarily on gastric emptying and small intestinal transit time, resulting in an improved glucose tolerance and a decreased digestion of starch; second, on colonie transit time and large bowel functions due to fermentation by ceco‐colonic microbial flora or bulking action.

The so‐called soluble dietary fibers are fermented to a large extent by a wide variety of anaerobic bacteria that result in an increase in bacterial biomass, an increase in fecal mass, a change in intracolonic pH, and production of short chain fatty acids and various gases as metabolic end products. The insoluble fibers are only marginally fermented; they serve almost exclusively as bulking agents that result in shorter transit time and increased fecal mass.

The short chain fatty acids resulting from the colonie fermentation of dietary fiber are largely absorbed via the portal blood and reach both the liver and the peripheral tissues. They induce changes in glucose and fat metabolism leading to post‐prandial hypoglycemia and long‐term hypolipidemia.

Inulin and oligofructose are fructans with a degree of polymerization of 2 to 60 and 2 to 20. respectively. Due to the structural conformation of their osidic bridge ((3 2–1), they both resist the hydrolysis by human alimentary enzymes. Moreover, when reaching the colon, both inulin and oligofructose are almost quantitatively fermented almost exclusively by colonie bifidobacteria and bacteroides. Such an extensive fermentation causes an increase in fecal bacterial biomass, a decrease in ceco‐colonic pH. and produces a large amount of fermentation products among which the short chain fatty acids that exert systemic effects on lipid metabolism.

Thus, both inulin and oligofructose have most of the characteristics of a dietary fiber and the proposal is made to classify them as such. Moreover, they are bifidogenic factors, because, due to still unknown reasons, they are primarily fermented by bifidobacteria.

It is concluded from this review that “nondigestible fructooligosaccharides.” even though they arc not included in the carbohydrate fraction that is quantified as dietary fiber by classic analytical methods, have most of the physiological effects of a dietary fiber. Because it has become necessary for the consumer to be informed clearly and specifically on the nature and the beneficial effects of all fermentable carbohydrates that will “feed” their colon, it is suggested that food labeling should be extended to include such products in the dietary liber fraction.     

Nutrition of infants and young children (one to three years) and its effect on later health: A systematic review of current recommendations (EarlyNutrition project)

Background. EarlyNutrition (www.project-earlynutrition.eu) is an international research project investigating the effects of early nutrition on metabolic programming.

Objective. To summarize, by performing a systematic review, current standards, recommendations, guidelines, and regulations (hereafter, referred to as documents) on the nutrition of children up to three years of age. Special emphasis was placed on long-term effects of early nutrition, such as the risk of cardiovascular disease, hypertension, overweight, obesity, metabolic syndrome, diabetes, or glucose intolerance.

Methods. MEDLINE, selected databases, and websites were searched for documents published between 2008 and January 2013.

Results. Forty two documents met the inclusion criteria. The strongest and most consistent evidence for a protective, long-term effect was documented for breastfeeding. Also, limiting the intake of sodium and rapidly absorbed carbohydrates, use of a specific meal pattern, reducing the consumption of saturated fatty acids by replacing them with polyunsaturated fatty acids, and lowering the intake of trans fatty acids, seems beneficial. Many documents did not evaluate long-term outcomes of interest to us, or reported insufficient or imprecise data. Inconsistency in recommendations for some outcomes and research gaps were identified.

Conclusions. Our findings may serve as a helpful tool in planning further research, preventive actions against important diet-related diseases, and guidelines improvement.     

The regulatory environment past and future — incentive or impediment to developments in food science and technology: A perspective from FDA∗

The best system for protecting public health is one that involves two layers of control before food reaches the consumer. The first layer of control is the industry's clear responsibility to prepare food that is safe. The second layer of control is the monitoring that is provided by government to ensure that the industry is doing its job and is in fact producing safe food.

While some may view this “second layer” as an impediment in the development and marketing of new technologies, there is another way to look at the “regulatory environment”. The regulatory environment itself, is not an impediment to the development of food science and technology.

The regulatory environment, with all its components — scientists, consumers, industry, and Congress — defines “safety” within the context of today's technology, scientific capability, and tolerance level of the lay public. The entire regulatory environment serves to guide the development of food science and technology by providing signposts, in the form of scientifically sound regulatory decisions. The scientific basis of these decisions becomes building blocks on which to rest further refinement of the technology, product, ingredient, or packaging material or on which research in related technologies or research in innovative directions can build.

This scientific groundwork becomes very important as more and more companies move away from having self‐contained research laboratories toward using commercial laboratories and academic institutions, as well as participating in cooperative research endeavors to meet food safety and product development research needs. These changes in the way industry is doing business today clearly indicate a direction that will impact on the “regulatory environment” in the next few years — a direction that will include deeper commitment of private/public sector cooperation in generating the data and information that defines safety for any given technology or product. The shift to commercial labs and academic institutions is occurring at the same time the consumer continues to believe that food is “safe”, novel technologies and products are entering the market at an ever increasing rate, the market is moving toward a more global food supply, and significant changes are taking place in the food safety/inspection infrastructure. To meet these challenges, the academic institutions will take on more importance. To the extent that food scientists from industry dissipate, other food scientists — particularly those in academic settings — must assume additional responsibilities. Further changes will come in the way we do business.

In the words of Robert McVicker, Kraft General Foods’ Dr. VP of Technology, Quality Assurance and Scientific Relations, describing one public/private sector cooperative effort, the National Center for Food Safety and Technology, “It is clear that in forming the National Center our key objective is the generation and fostering of scientific and technical knowledge and the exchange of this knowledge among the agency, industry, and academic partners. In working side by side, I believe we will learn that our goals are very similar and are, in fact, identical. Through partnerships and strategic alliances such as we are forging, we will continue to deliver safe and wholesome foods to American consumers.”     

魔芋葡甘聚糖基活性纳米复合膜的构建及性能研究

目的 对魔芋葡甘聚糖(konjac glucomannan, KGM)薄膜进行改良。方法 以KGM为基质, 棉花纤维素纳米晶须(cellulose nanocrystals, CNC)作为增强剂, 马尾藻多酚(phlorotannins from Sargassum, PS)为抗菌抗氧化剂, 通过物理性能、自由基清除能力和抗菌性检测, 筛选KGM/CNC/PS活性纳米复合膜包装材料。该包装材料运用在鲜猪肉保鲜上时, 以菌落总数(total bacterial count, TBC)、总挥发性盐基氮(total volatile base nitrogen, TVB-N)、硫代巴比妥酸反应物(thiobarbituric acid reactive substances, TBARS)、pH等指标判断鲜猪肉腐败变质程度。结果 当质量比KGM:CNC:PS=100:9:9.81 (KCP-9)时, KGM/CNC/PS活性纳米复合膜的热稳定性、力学性能、水蒸气阻隔性能相对其他比例的复合膜显著提高, KGM:CNC:PS=100:9:18.53 (KCP-17)时, 抗氧化和抗菌性能最佳, 后者运用在鲜猪肉上时, TBC、TVB-N、TBARS、pH等指标明显优于对照组中不使用任何保鲜剂的猪肉, 可延缓鲜猪肉腐败变质速度, 延长其货架期。结论 当KGM:CNC:PS=100:9:18.53 (KCP-17)时, KGM/CNC/PS活性纳米复合膜包装材料具有良好的抗氧化和抗菌性, 在食品保鲜领域具有潜在的应用前景, 本研究可为提高食品包装材料机械性能、抗菌性和抗氧化能力研究提供参考。     

State of art of nanotechnology applications in the meat chain: A qualitative synthesis

Background: Nanotechnology is a promising area in industry with a broad range of applications including in the agri-food sector. Several studies have investigated the potential benefits deriving from use of nanomaterials in the context of the whole food chain drawing scenarios of benefits but also potential for concerns. Among the agri-food sector, animal production has potential for nanomaterial application but also for safety concerns due to the possibility of nanomaterial accumulation along the farm-to-fork path.

Scope and Approach: The aim of this work was to define the state of the art of nanomaterial applications in the animal production sector by assessing data belonging to recently publishes studies. To do this, a qualitative synthesis approach was applied to build a fit-for-purpose framework and to summarise relevant themes in the context of effectiveness, feasibility and health concerns.

Key findings and conclusions: Nanomaterials have potential for use in a wide range of applications from feed production and farming to food packaging, including several detection tools designed for the benefit of consumer protection. The current high degree of variability in nanomaterials tested and in study designs impairs external validation of research results. Further research is required to clearly define which safe nanomaterial applications have the potential to reach the market.     

On the presence of Inulin and Oligofructose as natural ingredients in the western diet

The classic definitions of inulin and oligofructose are constructively criticized. It is observed that inulin cannot unequivocally be described as a polydisperse 1‐kestose‐based (GF_n) β(2 ? 1) linear fructan chain, but that inulin always contains small amounts of F_m and branched molecules. This review article describes the presence of inulin and oligofructose in common foodstuffs. Historical data on human consumption add an extra dimension.

Modern analytical techniques (HPLC, LGC, HPAEC‐PAD) are used to check the variety of data mentioned in the literature throughout the past century. Methods to determine inulin and oligofructose in natural foodstuffs (cereals, fruit, and vegetables) are optimized and used to determine the loss of inulin during storage and during preparation of the food.

These findings allow quantification of the amount of inulin and oligofructose in the average daily western diet. The daily per capita intake is estimated to range from 1 to 10 g, depending on geographic, demographic, and other related parameters (age, sex, season, etc.).

Inulin and oligofructose are not measured by classic methods of dietary fiber analysis and consequently are often not mentioned in food tables. Their significant contribution (1 to 10 g/d/per capita) to the dietary fiber fraction (recommended at 25 g/d/per capita) is not taken into account in any nutritional recommendations. In view of this, inulin and oligofructose deserve more attention, both in food composition tables and in diet or nutrition studies.     

Critical assessment of the epidemiological data concerning the impact of antioxidant nutrients on cancer and cardiovascular disease

Epidemiological studies strongly suggest that high intakes of foods rich in beta carotene, as well as those rich in vitamin E or vitamin C, reduce the risk of some but not all cancers and cardiovascular disease. It is difficult to determine whether these antioxidant nutrients per se are the sole protective agents or whether other factors associated with foods containing them contribute to the foods’ protective effects.

With respect to vitamin E, a number of studies where dietary and supplementary vitamin E were clearly differentiated, a reduced risk of certain cancers or cardiovascular disease from supplemental vitamin E but not from dietary vitamin E was demonstrated. This provides strong presumptive evidence that high intakes of vitamin E per se provide a health benefit.

Only a few intervention studies with specific nutrients are available and results are inconsistent.     

Critical review of methods for risk ranking of food-related hazards,based on risks for human health

This study aimed to critically review methods for ranking risks related to food safety and dietary hazards on the basis of their anticipated human health impacts. A literature review was performed to identify and characterize methods for risk ranking from the fields of food, environmental science and socio-economic sciences. The review used a predefined search protocol, and covered the bibliographic databases Scopus, CAB Abstracts, Web of Sciences, and PubMed over the period 1993–2013.

All references deemed relevant, on the basis of predefined evaluation criteria, were included in the review, and the risk ranking method characterized. The methods were then clustered—based on their characteristics—into eleven method categories. These categories included: risk assessment, comparative risk assessment, risk ratio method, scoring method, cost of illness, health adjusted life years (HALY), multi-criteria decision analysis, risk matrix, flow charts/decision trees, stated preference techniques and expert synthesis. Method categories were described by their characteristics, weaknesses and strengths, data resources, and fields of applications.

It was concluded there is no single best method for risk ranking. The method to be used should be selected on the basis of risk manager/assessor requirements, data availability, and the characteristics of the method. Recommendations for future use and application are provided.     

Genetic Resources of Cannabis sativa L. in the Collection of the Gene Bank at INF&MP in Poznan

The hemp gene collection at the Institute of Natural Fibres & Medicinal Plants is unique in Poland in terms of diversity and the number of gathered accessions. It holds about 150 accessions from various regions of the world.

It includes mono and dioecious forms representing different degree of adjustment to climate-soil conditions and also local ecotypes and breeding lines of stable genotype, distinctive because of a single treat e.g. Δ⁹THC and cellulose and fiber content, yielding, beginning of flowering date, and full maturity date.

Each accession is characterized with the morphological and biological features and use value.

The INF&MP collection makes a valuable source for breeders when selecting useful parental components and also secures breeders’ achievements.     

Water activity,water glass dynamics,and the control of microbiological growth in foods

Water is probably the single most important factor governing microbial spoilage in foods, and the concept of water activity (a_w) has been very valuable because measured values generally correlate well with the potential for growth and metabolic activity. Despite some drawbacks (e.g., solute effect), the concept of a_w has assisted food scientists in their effort to predict the onset of food spoilage as well as to control food‐borne disease hazards in food products. In the last decade the concept of a_w has been challenged. It has been suggested that reduced‐moisture food products (e.g., low and intermediate) may be nonequilibrium systems and that most of them are in the amorphous metastable state, which is very sensitive to changes in moisture content and temperature. It has been proposed that the glass transition temperature T_g (temperature at which the glass‐rubber transition occurs), is a parameter that can determine many product properties, the safety of foods among them. The concept of water dynamics, originating in a food polymer science approach, has been suggested instead of a_w to better predict the microbial stability of intermediate‐moisture foods. The usage of a_w to predict microbial safety of foods has been discouraged on the basis that (1) in intermediate‐moisture foods the measured water vapor pressure is not an equilibrium one, and because a_w is a thermodynamic concept, it refers only to equilibrium; and (2) the microbial response may differ at a particular a_w when the latter is obtained with different solutes.

This review analyzes these suggestions on the basis of abundant experimental evidence found in the literature. It is concluded that nonequilibrium effects (e.g., inability of water to diffuse in a semimoist food) appear to be in many cases slow within the time frame (food's shelf life) of the experiments and/or so small that they do not affect seriously the application of the a_w concept as a predictor of microbial stability in foods.

The claims that a food science polymer approach to understanding the behavior of aqueous sugar glasses and concentrated solutions may be used to predict the microbial stability of food systems is not substantiated by experimental evidence. This approach does not offer, at the present time, a better alternative to the concept of a_w as a predictor of microbial growth in foods.

It is also recognized that a_w has several limitations and should be always used carefully, and this must include precautions regarding the possible influences of nonequilibrium situations. This aspect may be summarized by simply saying that anyone who is going to employ the term water activity must be aware of the implications of its definition.     

魔芋葡甘聚糖及其衍生物肠道益生性的体外发酵评价

目的：评价魔芋葡甘聚糖（konjac glucomannan,KGM）及其衍生物脱乙酰基魔芋葡甘聚糖（D-KGM）、魔芋葡甘露低聚糖（konjac oligosaccharide,KOS）的肠道益生性。方法：分别以1 g/100 mL的KGM、KOS和D-KGM为碳源,通过小鼠盲肠内容物体外厌氧发酵,测定发酵液的pH值、微生物和短链脂肪酸,评价肠道益生效果。结果：与阳性对照组（以葡萄糖作为碳源）相比,KGM和KOS发酵液pH值明显降低,短链脂肪酸（short-chainfatty acids,SCFAs）和乳酸菌、双歧杆菌的数量显著增加,肠道潜在致病菌（大肠杆菌、梭状杆菌、拟杆菌）的增殖不明显,而D-KGM发酵液中pH值、肠道微生物、SCFAs与阴性对照组（不含碳源）均无显著性差异。结论：KOS和KGM具有显著的肠道益生性,而D-KGM没有肠道益生性。