In vitro digestion kinetics and bioaccessibility of starch in cereal food products

The study of starch digestion in cereal-based products is essential since the extent and rate of hydrolysis affects the glycemic index associated with several food-related diseases. Besides, a unique matrix is usually studied and many variations of in vitro techniques (e.g. enzymes, pH, food:enzymes ratio) are selected, then comparison of results became difficult. The recently published INFOGEST in vitro static method with international consensus (Minekus et al., 2014) was applied to several cereal-based products to address whether it is suitable for analysis of starch hydrolysis kinetics. Bread, pasta and cookies were selected taking into account the analysis of different cereal matrixes, including gluten-free products. White bread presented the highest in vitro starch hydrolysis (87%) showing significant differences compared to gluten-free bread (76.5%). Refined flour sheeted pasta (72.6%), whole-wheat extruded pasta (92.0%) and gluten-free pasta (54.3%) showed differences in the extent and rate of hydrolysis. Cookie samples presented the lowest starch hydrolysis (∼45%). The starch availability was estimated by the dializability method, which measures the maltose equivalents dialyzed after simulating digestion. Starch dializability was 35%, 25% and 15% on average for bread, pasta and cookie samples respectively, with positive correlation with rapidly digested starch. The tested in vitro method allowed discriminating the effect of different processing techniques, product types and formulation of the three most common cereal-food matrixes in starch digestion.     

NaCl胁迫对藜麦幼苗生长和生理指标的影响

为揭示藜麦耐盐生理机制,本研究分别采用0、50、100、150、200、250、300 mmol/L NaCl处理藜麦,于处理6、12、24、48、72、96 h后测定藜麦株高、生物量、叶绿素及类黄酮的含量。结果表明:低浓度NaCl胁迫及短时间NaCl处理(50~150 mmol/L NaCl、6~48 h)促进藜麦的生长,高浓度NaCl胁迫及长时间NaCl处理(200~300 mmol/L NaCl、72~96 h)则抑制其生长;藜麦叶片叶绿素和类黄酮含量随NaCl浓度升高呈先升后降趋势,均在100 mmol/L NaCl处理下有最大值,且随处理时间的增加呈先降后升趋势,表明适宜的NaCl浓度和处理时间会促进叶绿素和类黄酮在藜麦体内的积累,增强其抗氧化能力。     

Response surface optimization of mechanochemical-assisted extraction of flavonoids and terpene trilactones from Ginkgo leaves

Mechanochemical-assisted extraction (MCAE) method was developed for extraction of flavonoids and terpene trilactones from Ginkgo leaves. The MCAE parameters and the antioxidant activities of Ginkgo biloba extract (GBE) were investigated. Through response surface methodology design experiments, the processing conditions were optimized as follows: amount of solid reagent (NaHCO₃) 21%, milling time 7.5 min, and ratio of solvent to solid 33 mL/g. Under these conditions, the yields of flavonoids and terpene trilactones in GBE were 6.83 mg/g and 1.72 mg/g, respectively. Compared with the heat reflux extraction method, the yields of flavonoids and terpene trilactones are higher, and the extraction time was significantly shortened. What is more, the MCAE method only used water as solvent. GBE of MCAE possessed notable antioxidant activity with IC₅₀ values of 11.7 and 13.8 μg/mL, respectively.     

Insights from in vitro exploration of factors influencing iron,zinc and provitamin A carotenoid bioaccessibility and intestinal absorption from cereals

Developments in genetics, agronomics and processing has positioned staple cereals as important sources of iron, zinc and provitamin A (pVA) carotenoids for nutritionally vulnerable populations. Significant effort has been placed on understanding the bioavailability of these micronutrients from cereal foods, including the exploration of underlying mechanisms by which their bioavailability can be modified. While micronutrient bioavailability is preferably assessed in clinical trials, relevant in vitro digestion and intestinal cell culture models have been applied to study effects of genetic, agronomic, post-harvest and food processing on micronutrient bioavailability. This review (1) critically assesses the application of in vitro models in the exploration of mechanisms associated with iron, zinc and provitamin A carotenoid bioaccessibility and intestinal absorption from cereal foods, and (2) identifies remaining gaps in order to frame future strategies to improve the nutritional impact of cereal foods.     

Effect of different soaking conditions on inhibitory factors and bioaccessibility of iron and zinc in pearl millet

Pearl millet was decorticated to obtain a bran rich and endosperm rich fraction. The two fractions were soaked in solutions with varying pH. Pearl millet grains were germinated and steamed followed by decortication to obtain two fractions. It was observed that bran rich fractions contained high concentrations of iron, zinc, polyphenols, phytic acid, fibre and flavonoids. Soaking for short duration of 3 h did not result in major mineral losses but decreased the inhibitory factors which depended on the pH. Alkaline soaking decreased flavonoid content by 62.7% in the endosperm rich fraction, while acidic soaking decreased phytic acid content to the maximum in the bran rich fraction. Combination of treatments like germination and heat decreased the phytate content to the maximum in the endosperm rich fraction. Acidic conditions improved zinc bioaccessibility in the bran rich fraction (35%) and iron bioaccessibility (2.5%) in the endosperm rich fraction. Bran rich fraction from germinated grain also had enhanced bioaccessibility of both the minerals but comparatively lesser when compared to soaking under acidic conditions. Soaking the grain components under slightly less than neutral conditions also decreased some of the inhibitory factors and improved the zinc bioaccessibility to some extent in the bran rich fraction.     

Carotenoid bioaccessibility from whole grain and decorticated yellow endosperm sorghum porridge

Sorghum is a staple crop and a potential dietary source of carotenoids in semi-arid regions of Africa, but information on the bioavailability of these pigments is limited. This study aimed at exploring the effects of agronomic manipulation on sorghum carotenoid contents at selected stages of kernel development and maturation and assessing carotenoid bioaccessibility from matured yellow-endosperm sorghum varieties (P88 and P1222), by comparing porridge made from sorghum whole and decorticated milled grains. Carotenoid content of sorghum milled fractions ranged from 2.90 to 7.22 mg/kg in P88 unbagged decorticated flour, at 50 and 30 days after half bloom (DAHB) respectively, to 9.87-13.69 mg/kg in bagged decorticated bran fractions in P88, at 50 and 30 DAHB respectively. Maize milled fractions were significantly (P < 0.05) higher in carotenoid content than all sorghum products. Bagging increased sorghum carotenoid content by 8-184% vs. unbagged panicles. Carotenoid bioaccessibility was generally higher from sorghum (63-81%) compared to maize (45-47%). Micellarization of xanthophylls (75%) was more efficient than carotenes (52%) in sorghum, while they were similar in maize (40-49%). These results suggest that the higher bioaccessibility of sorghum carotenoids combined with efforts to enhance sorghum carotenoid content may allow for sorghum to provide similar levels of bioaccessible carotenoid pigments as common yellow maize.     

Antioxidant and anti-inflammatory capacity of bioaccessible compounds from wheat fractions after gastrointestinal digestion

Wholegrain consumption is associated with several health benefits, in contrast to the consumption of refined grains. This can partly be related to the antioxidant compounds in the outer parts of the grain kernel. The bioaccessibility of these antioxidant compounds from the wholegrain matrix during gastrointestinal digestion is crucial for their absorption and bioavailability. In the current study, the bioaccessible compounds from aleurone, bran and flour were obtained from a dynamic in vitro model of the upper gastrointestinal tract. They were collected at 1 h time intervals to assess their antioxidant capacity (TEAC assay) and also their anti-inflammatory effect (TNF-α reduction in U937 macrophages stimulated with LPS). The bioaccessible compounds from aleurone had the highest antioxidant capacity and provided a prolonged anti-inflammatory effect, shown by the TNF-α reduction of a relatively late time-interval (3–4 h after start of digestion). The contribution of ferulic acid to those effects was minor due to its low bioaccessibility. Aleurone seems a promising wheat fraction for cereal products with a healthy added value.     

Interaction of vitamin C and flavonoids in elderberry (Sambucus nigra L.) during juice processing

A field experiment and two oxidation experiments in the laboratory were carried out. The content of the major anthocyanins, cyanidin-3-glucoside (Cy-3-G) and cyanidin-3-sambubioside (Cy-3-Sa), in the fresh fruits from the 13 cultivars were from 361 to 1266 and from 269 to 656 mg/100 g, respectively. The two minor anthocyanins, cyanidin-3-sambu-bioside-5-glucoside (Cy-3-Sa-5-G) and cyanidin-3,5-diglucoside (Cy-3.5-dG), occurred in concentrations between 5 and 47 mg/100 g. The content of ascorbic acid and quercetin in the fresh fruits of the cultivars varied from 6 to 25, and from 29 to 60 mg/100 g, respectively. Purging of the elderberry juice with N2 and/or addition of ascorbic acid reduced the oxidative degradation rate of the two major anthocyanins and quercetin. Ascorbic acid protected the anthocyanins, but not quercetin from oxidative degradation. Mixing of fruits with air during processing and even a low content of oxygen in the juice before tapping must be avoided by appropriate steps during processing. Improvement of the nutritional value of the elderberry juice and increased protection of anthocyanins against oxidative degradation may potentially be obtained by selection of cultivars with a high content of ascorbic acid.     

Total phenolics,flavonoids, antioxidant capacity in rice grain and their relations to grain color,size and weight

Total phenolics, flavonoid contents and antioxidant capacity from a wide collection of rice germplasm were measured, and their relations to grain color, grain size and 100-grain weight were investigated. Highly significant genotypic differences were observed in total phenolics, flavonoid contents and 2,2-azino-bis-(3-ehylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical cation antioxidant capacity. They displayed an increasing order in the white rice, red rice and black rice, yet several white rice had higher phenolics and flavonoids contents than the red rice. Significant positive pair-wise correlations were found among the phenolics, flavonoid contents and antioxidant capacity, and the coefficient between the phenolic contents and antioxidant capacity was extremely high (r = 0.96). Among all rice accessions, the grain color parameters had negative correlations with the phenolics, flavonoid contents and antioxidant capacity (p < 0.001). The negative correlation between a* and antioxidant capacity, and the positive correlation between H° and antioxidant capacity were consistent within the respective white rice and red rice groups. Flavonoid contents had positive correlation with grain length and length to width ratio, and had negative correlation with the 100-grain weight among all rice accessions. It was also found that 100-grain weight still had negative correlations with phenolics, flavonoid contents and antioxidant capacity within the white rice genotypes. These relationships may serve as indexes to indirectly select breeding lines high in the phenolics, flavonoids and antioxidant capacity. Principal component analysis including the information for phenolics, flavonoids, antioxidant capacity, grain color parameters, grain size and 100-grain weight extracted five principal components that explained 83.7% of the total variances. The results of this study may provide new opportunities for rice breeders and eventually commercial rice growers to promote the production of rice with enhanced nutritional quality.     

Influence of baking and in vitro digestion on steryl ferulates from wheat

So far, data on absorption and metabolism of steryl ferulates from edible sources is scarce. Therefore, the impact of enzyme-aided baking and in vitro digestion was examined in this study. Wheat flours and wheat breads were subjected to a static in vitro digestion model and changes in the contents of steryl ferulates and free sterols (possible hydrolysis products of steryl ferulates) were monitored. Baking degraded steryl ferulates at a similar rate in all types of breads (43–47%) compared to the corresponding flours, while baking induced changes in free sterols showed no clear pattern. In vitro digestion provoked five folds lower content of steryl ferulates in flours than in breads and it also resulted in significant free sterol accumulation. Interestingly, bioaccessibility (0.01–0.25%) was not influenced by the cereal matrix. The four steryl ferulate species, which were detected in wheat, showed similar hydrolysis rates during digestion. As baking had a significant impact on the steryl ferulate content of wheat, we suggest that both raw and processed sources should be considered further in vitro, animal or human trials, when studying the metabolic fate of steryl ferulates.     

不同产地黑豆黄酮提取物的抗氧化能二勾比较研究

目的研究山东、黑龙江、甘肃和河南产地黑豆的黄酮提取物抗氧化能力,为兑合理开发提供理论依据。方法以抗坏血酸（Vc）作为阳性对照,利用Fenton反应测定其对羟自由基（·OH）的清除能力。并用铁氰化钾还原法测定其总还原能力。结果各产地黑豆的黄酮提取物均具有抗氧化能力,并与其浓度呈正相关。还原能力的顺序为山东〉甘肃〉河南〉黑龙江。其中山东黑豆的黄酮提取物的还原能力与Vc持平,其他三个地区的还原能力较低。结论产地对黑豆中黄酮提取物的抗氧化还原能力的影响较大,山东产黑豆表现最好,作用可达到Vc的效果。     

Effect of forage hydration on lag time during in vitro digestion of meadow hay

Digestion of plant cell wall has been observed to be a first-order process with an initial lag. Lag is defined as the period of time immediately after forage is exposed to the fermentive environment during which digestion does not occur or occurs at a greatly reduced rate. The effects of forage hydration on lag were investigated by focusing on the first 20 h of in vitro digestion of meadow hay. Samples were hydrated for 0, 1, and 16 h before fermentation. Digestion kinetics was estimated by both a first-order kinetics model (KM) and an increasing relative-rate model (RRM). Model parameters were obtained using a non-linear least-squares procedure. The effect of forage hydration was significant, especially for the 16-h treatment. The RRM produced a better fit for the data from each treatment, and a better fit was obtained when each data set was analysed separately.     

Bioactive Compounds and Antioxidant Capacity of Strawberry Jams

Strawberries represent the main source of ellagic acid derivatives in the Brazilian diet. They are also good sources of flavonoids, mainly anthocyanins, and phenolic acids, to which many beneficial effects have been attributed. However, as the fruit is not available all the year, the objective of this work was to determine whether the jams could also represent a good source of bioactive compounds. In the current study, five different commercially available strawberry jams were characterized in relation to flavonoids, total phenolics, free and total ellagic acid contents, and antioxidant capacity. Anthocyanins were detected only in two jams at very low content. Kaempferol glycosides were the main flavonoids present (from 0.38 to 1.05 mg/100 g fresh weight, FW), while quercetin glycosides were present in the range 0.14–1.20 mg/100 g FW. Free and total ellagic acid content ranged from 0.4 to 2.9 mg/100 g FW, and from 17.0 to 29.5 mg/100 g FW, respectively. Total phenolics varied from 58 to 136 mg/100 g FW, and the antioxidant capacity from 0.55 to 0.76 μmol BHT (Butylhydroxytoluene) equivalents/g FW. Overall, results indicated that jams can also represent a good source of antioxidant compounds, although compared to the fruit important losses seem to occur.     

In vitro antioxidant activity of ragweed (Ambrosia artemisiifolia L., Asteraceae) herb

The antioxidant activity in 70% aqueous acetone extracts of the herb of Ambrosia artemisiifolia L., Asteraceae was evaluated with regards to total polyphenol and flavonoid contents. Antioxidant activity has been assessed by two commonly used in vitro tests, based on determination of ferric-reducing antioxidant power (FRAP assay) and DPPH free radical scavenging ability (DPPH assay), against butylated hydroxytoluene (BHT), ascorbic acid and quercetin, which were used as positive control substances. The results of both antioxidant tests showed that the plant material expressed a considerable activity (DPPH IC₅₀ = 27.6 μg/ml; FRAP value = 2.37 mmol Fe²⁺/g), attributed to both flavonoid aglyca and resembling glycosides, as verified by dot-blot TLC analysis.     

Determination of oil palm fresh fruit bunch ripeness—Based on flavonoids and anthocyanin content

Non-destructive and real-time oil palm fresh fruit bunch (FFB) grading systems are of major exploratory concern for researchers in the oil palm industry. The objective is to reduce time, labour, costs, and most importantly, to increase the oil extraction rate, in order to achieve a good quality of palm oil at a more acceptable price. This research investigates the potential of flavonoids and anthocyanins as a predictor to classify the degree of oil palm FFB ripeness. This paper also discusses the relationship between these predictors and the ripeness categories period. One hundred and eighty oil palm FFB samples were collected from a private plantation in Malaysia, according to three maturity categories i.e., ripe, under-ripe, and over-ripe. Each sample was randomly scanned 10 times, both front and back using a hand-held Multiplex^®3 multi-parameter fluorescence sensor. The results show that flavonoid and anthocyanin content decreased from immature to over mature oil palm FFBs. Overall, the relationship using Pearson's correlation between flavonoids and anthocyanins was r² = 0.84 and the most outstanding relationship accuracy was at the over-ripe stage, at 90%. Statistical analysis using analysis of variance (ANOVA) and pair-wise testing proved that both predictors gave significance difference between under-ripe, ripe, and over-ripe maturity categories. This shows that both predictors can be good indicators to classify oil palm FFB. Classification analysis was performed by using both predictors together and separately through several methods. The highest overall classification accuracy was 87.7% using a Stochastic Gradient Boosting Trees model and with both predictors. The other classification methods used either independent or both predictors together and gave various results ranging from 50 to 85% accuracy. This research proves that flavonoids and anthocyanins can be used as predictors of oil palm maturity classification.     

Phenolic Composition,Antioxidant Capacity and <Emphasis Type="Italic">In Vitro</Emphasis> Cancer Cell Cytotoxicity of Nine Prickly Pear (<Emphasis Type="Italic">Opuntia</Emphasis> spp.) Juices

Juices of nine prickly pears (Opuntia spp.) were characterized in terms of color, acidity, sugar content, phenolics, flavonoids, betalains and antioxidant activity and tested in vitro against four cancer cell lines. The juices had pH′s, acidities and sugar ranging from 4.27 to 5.46, 0.03 to 0.27% and 8 to 14.7°Brix, respectively. Juices also varied in color from white to purple and contained total phenolics, flavonoids, betaxanthins, betacyanins and antioxidant capacity ranging from 22 to 226 μg gallic acid eq/g, 95 to 374 μg quercetin eq/g, 3 to 189 μg/g, 1.6 to 300 μg/g and 17 to 25 micromoles Trolox eq./mL, respectively. Among the cancer lines tested, viability of prostate and colon cells were the most affected. Moradillo contained the highest flavonoids and diminished both prostate and colon cancer cell viability without affecting mammary or hepatic cancer cells. Rastrero reduced the growth of the four cancer cell lines without affecting normal fibroblast viability. The research shows intervarietal differences among prickly pears in terms of juice properties and phytochemicals that could prevent oxidative stress and cancer.     

花生不同品种叶片类黄酮含量和相关合成酶活性对PEG胁迫的响应

以花生品种花17、农大818、丰花5号和山花11号为试材,聚乙二醇(PEG)室内砂培法模拟干旱胁迫,研究20%PEG胁迫下花生幼苗叶片中类黄酮含量及相关合成酶活性的变化。20% PEG开始处理后,随胁迫时间延长,幼苗叶中类黄酮含量逐步上升,在胁迫9h达到高峰,之后逐步下降至对照水平,农大818、丰花5号和山花11号均在处理后72h降至对照水平,花17在36h降至对照水平。PEG开始处理后苯丙氨酸解氨酶（PAL）、查尔酮合成酶（CHS）、查尔酮异构酶（CHI）酶活性均逐渐提高,6h后CHS、CHI酶活性达到高峰,9h后PAL酶活性达到高峰,之后下降,4个品种趋势一致。分析表明PEG处理后山花11号和丰花5号的合成酶具有较高的活性和积累速率是其类黄酮快速大量合成的原因,而农大818 CHS酶活性和PAL酶活性提高速率较低限制了其类黄酮的积累,3种酶的活性和积累速率均较低导致花17叶中类黄酮合成少,含量提高慢。相关分析表明PEG胁迫下PAL、CHS、CHI共同调控类黄酮的代谢,胁迫引起PAL、CHS、CHI酶活性改变是类黄酮含量变化的原因。     

Interrelation between mechanical and biological aeration in starch-based gluten-free dough systems

Alternative aeration and gas stabilization strategies are required for the production of starch-based cellular food systems, such as gluten-free bread. In the present study, density and temperature were monitored in mixing experiments without yeast, aiming at maximum mechanical aeration. Additionally, the same trials were performed with subsequent biological aeration, including yeast fermentation and baking. As a result, the gas volume fraction was elevated to 21%, instead of 6% with conventional kneading. Reducing the water content from 120% to 90% (flour/starch weight base) raised dough viscosity and temperature without affecting the state of aeration. The bread volume was strongly influenced by the dough temperature after mixing (R² = 0.98), since it depended on yeast activity. The implemented process is suitable to aerate starch-based dough systems mechanically and enables the production of gluten-free bread with high volume and fine pores.     

Prolonged tempe-type fermentation in order to improve bioactive potential and nutritional parameters of quinoa seeds

The effect of 40 h solid-state fermentation with Rhizopus oligosporus on selected parameters of white and coloured quinoa was studied, as compared to standard (30 h) product and cooked seeds.The reducing power (RP) and the activity against synthetic free radicals of standard tempe were higher by on average 140% (white) and 64% (coloured quinoa) than that of cooked seeds. The OH scavenging activity was increased by more than 7 fold (white), and over 2 fold (coloured quinoa). Prolongation of the fermentation caused further improvement in this potential, on average by 27% (OH, RP) and 24% (DPPH, ABTS⁺ assays). The soluble phenols i.e. vanillic acid, protocatechuic acid and rutin levels in 40 h tempe were significantly higher than in cooked quinoa. Fermented products contained 470% (white) and on average 150% (coloured quinoa) more riboflavin and 100% more thiamine (white quinoa) than cooked seeds. The levels of total protein, free amino acids and proteins releasable during the in vitro digestion, were improved as a result of 40 h fermentation. The essential amino acids profile of quinoa tempe was consistent with the reference pattern.The prolonged tempe-type fermentation of quinoa can be recommended as a method of the value-added food production.     

Enzyme pretreatment and negative pressure cavitation extraction of genistein and apigenin from the roots of pigeon pea [Cajanus cajan (L.) Millsp.] and the evaluation of antioxidant activity

An enzyme pretreatment and negative-pressure cavitation extraction (E-NPCE) method was investigated for extraction genistein and apigenin from pigeon pea roots. The important parameters involved in E-NPCE process were optimized by single-factor experiments and then critical parameters were investigated by a 2³ full factorial central composite design (CCD) to optimize extract conditions. Under optimal conditions, the yields of genistein and apigenin were 0.628 mg/g and 0.359 mg/g, which represented an increase of 44.70% and 53.05%, respectively, compared to standard NPCE. Furthermore, from DPPH scavenging activity test the extract of E-NPCE showed better antioxidant activity than these of other methods. The results demonstrated that E-NPCE would have lower energy consumption, higher efficiency and could be an alternative method for natural compounds extraction.