Characterization and nutritional valorization of agricultural waste corncobs from Italian maize landraces through the growth of medicinal mushrooms.

The research investigates the potential use of maize cobs (or corncobs) from five genotypes, including the B73 inbred line and four locally cultivated landraces from Northern Italy, as substrate for implementing Solid State fermentation processes with four Medicinal Mushrooms (MMs). The corncobs were characterized based on their proximate composition, lignin, phenolics content (both free and bound), and total antioxidant capacity. Among the MMs tested, Pleurotus ostreatus and Ganoderma annularis demonstrated the most robust performance. Their growth was parametrized using Image Analysis technique, and chemical composition of culture samples was characterized compared to that of corncobs alone. In all culture samples, the growth of MMs led to a significant reduction (averaging 40%) in the total phenolics contents compared to that measured in corncobs alone. However, the high content of free phenolics in the cobs negatively impacted the growth of P. ostreatus. The final MM-corncob matrix exhibited reduced levels of free sugars and starch (≤ 2.2% DW, as a sum) and increased levels of proteins (up to 5.9% DW) and soluble dietary fiber (up to 5.0% DW), with a notable trend toward higher levels of ß-glucan compared to corncobs alone. This research paves the way for the use of this matrix as an active ingredient to enhance the nutritional value of food preparations.

Lactic acid bacteria with cholesterol-lowering properties for dairy applications: In vitro and in situ activity.

Cholesterol-lowering activity is one of the most promising properties of lactic acid bacteria with probiotic characteristics. In the present study, 58 potentially probiotic lactic acid bacteria were tested for their ability to survive in vitro digestion and reduce cholesterol in a medium containing cholesterol and bile acids. The best-performing strains (Lactobacillus casei VC199, Lactobacillus paracasei ssp. paracasei SE160 and VC213, Lactobacillus plantarum VS166 and VS513, Enterococcus faecium VC223, and Enterococcus lactis BT161) resulted in a 42 to 55% reduction of the cholesterol level in broth and were further tested in cheese manufacture. The cholesterol content in all the cheeses decreased with ripening. All the strains were present in the cheese at levels higher than 107 cfu/g until 60 d of ripening, the highest reductions (up to 23%) being obtained when Lb. paracasei ssp. paracasei VC213 and E. lactis BT161 were added during the cheese-making. The adjunct cultures had no negative effect on the sensory characteristics of the cheese. Thus, these strains with proven in vitro properties are good candidates for novel probiotic-containing formulations and could be used to functionalize foods such as dairy fermented products.

Phenylketonuric diet negatively impacts on butyrate production.

BACKGROUND AND AIMS: Phenylalanine (Phe) restricted diet, combined with Phe-free l-amino acid supplementation, is the mainstay of treatment for phenylketonuria (PKU). Being the diet a key factor modulating gut microbiota composition, the aim of the present paper was to compare dietary intakes, gut microbiota biodiversity and short chain fatty acids (SCFAs) production in children with PKU, on low-Phe diet, and in children with mild hyperphenylalaninemia (MHP), on unrestricted diet. METHODS AND RESULTS: We enrolled 21 PKU and 21 MHP children matched for gender, age and body mass index z-score. Dietary intakes, including glycemic index (GI) and glycemic load (GL), and fecal microbiota analyses, by means of denaturing gradient gel electrophoresis (DGGE) and Real-time PCR were assessed. Fecal SCFAs were quantified by gas chromatographic analysis. RESULTS: We observed an increased carbohydrate (% of total energy), fiber and vegetables intakes (g/day) in PKU compared with MHP children (p = 0.047), as well a higher daily GI and GL (maximum p < 0.001). Compared with MHP, PKU showed a lower degree of microbial diversity and a decrease in fecal butyrate content (p = 0.02). Accordingly, two of the most abundant butyrate-producing genera, Faecalibacterium spp. and Roseburia spp., were found significantly depleted in PKU children (p = 0.02 and p = 0.03, respectively). CONCLUSION: The low-Phe diet, characterized by a higher carbohydrate intake, increases GI and GL, resulting in a different quality of substrates for microbial fermentation. Further analyses, thoroughly evaluating microbial species altered by PKU diet are needed to better investigate gut microbiota in PKU children and to eventually pave the way for pre/probiotic supplementations.

Glycemic index and glycemic load of commercial Italian foods.

BACKGROUND AND AIM: The glycemic index (GI) and glycemic load (GL) are useful parameters in the nutritional classification of carbohydrate foods. Diets characterized by a low GI and/or a low GL have been repeatedly and independently associated with decreased risk of diabetes and other chronic diseases. The aim of this study is to report the GI and GL value of carbohydrate-rich foods available on the Italian market and mostly consumed in Italy. METHODS AND RESULTS: GI values were determined according to FAO/WHO (1997) and ISO (2010). Overall, the 141 commercial foods that were analyzed represent food categories that are the source of >80% carbohydrate intake in Italy. The food items chosen were based mainly on the market share of the brand within each food category and grouped into 13 food categories: 1) beverages: fermented milk drink, juice, smoothie, soft drink; 2) biscuits; 3) breads; 4) bread substitutes; 5) breakfast cereals; 6) cakes and snacks; 7) candy and confectionery; 8) cereals; 9) desserts and ice-creams; 10) marmalade and jam; 11) pasta; 12) pizza; 13) sugar and sweetener. CONCLUSION: This database of commercial Italian foods partly overcomes the lack of information on GI and GL of local foods, contributing to a better understanding of the association between GI/GL and health and providing a more informed choice to Italian consumers and health practitioners.

Effects of a synbiotic milk product on human intestinal ecosystem.

AIMS: To investigate the effect of prolonged consumption of a synbiotic milk (Synbiotic) containing Lactobacillus acidophilus (strain 74-2, 10(7) CFU ml(-1)), Bifidobacterium lactis (strain 420, 10(7) CFU ml(-1)) and 2% inulin on colonic ecosystem in healthy humans. METHODS AND RESULTS: A group of 26 healthy subjects, aged 22-47 years, participated in a 6-week placebo-controlled dietary intervention study. After a 2-week baseline period, in which all volunteers consumed 500 ml day(-1) of 2% skimmed milk (Placebo), the study was designed as a randomized, double-blind, two-armed parallel study in which 4-week consumption of 500 ml day portions of Synbiotic or Placebo were compared. Faecal microbial counts, pH, l-lactic acid and bile acid concentrations were assessed before and after the intervention. Synbiotic consumption significantly decreased faecal dry weight (P < 0.01) and l-lactic acid (P < 0.05) concentration, while significantly increased faecal bifidobacteria (P < 0.05) and lactobacilli (P < 0.01) counts. CONCLUSION: The tested synbiotic milk showed its synbiotic nature by enhancing the growth of bifidobacteria and lactobacilli. SIGNIFICANCE AND IMPACT OF THE STUDY: Scientific support to functional effect of a synbiotic milk.

Effect of consumption of a ready-to-eat breakfast cereal containing inulin on the intestinal milieu and blood lipids in healthy male volunteers.

OBJECTIVE: To investigate the effect of a breakfast cereal containing inulin on blood lipids and colonic ecosystem in normolipidemic young men. SETTING: Department of Food Science and Microbiology,University of Milan, Italy. SUBJECTS: Twelve healthy male volunteers, age 23.3 +/- 0.5 y, body mass index (BMI) 25.7 +/- 1.2 kg/m2 (mean +/- s.e.m.). INTERVENTIONS: Subjects consumed daily, for three periods of four weeks, 50 g of a rice-based ready-to-eat cereal (placebo) and the same cereal containing 18% inulin (test) in substitution of their habitual breakfast, then returned to the habitual diet (wash-out). They followed no other dietary restrictions. RESULTS: No changes in body weight, dietary habits, faecal and bile acid output, faecal short-chain fatty acid (SCFA) and faecal pH, were observed at the end of each period, whereas plasma total cholesterol and triacylglycerols significantly decreased at the end of test period by 7.9 +/- 5.4 (P < 0.05) and 21.2 +/- 7.8% (P < 0.005) respectively. Meal glucose tolerance test (MTT) resulted in the same incremental area under the curve for both cereals (IAUC test 124 +/- 35; placebo 118 +/- 33 mmol x min/l, ns). Inulin markedly enhanced breath H2 excretion (IAUC test 280 +/- 40; placebo 78 +/- 26 ppm x h, P < 0.005), as well as faecal concentration of L-lactate. Total facultative anaerobes significantly decreased after test, and bifidobacteria increased after correction for total anaerobes (P < 0.05). Changes in blood lipids were negatively correlated with bifidobacteria counts and positively with secondary bile acid excretion (P < 0.05). CONCLUSIONS: Inulin seems to have a lipid lowering potential in normolipidemic men possibly mediated by mechanisms related to colonic fermentation.

Resistant starch in the Italian diet.

Resistant starch (RS) has been defined as the sum of starch and starch-degradation products that reach the human large intestine (Champ, 1994), and it is now regarded as a sub-fraction of starch with a positive impact on colonic welfare and lipid metabolism. An early estimate of the RS intake in Europe gave an average value of approximately 4 g/d (Dyssler & Hoffem, 1994a). However, since no information is available for Italy, the aim of the present study was to estimate the intake of RS in the Italian diet by direct analysis of RS in a range of typical foods representing the main sources of starch intake in the country. The selection of representative foods and of food consumption data were based on published results of the National Food Consumption Study conducted during the 1980s by the National Institute of Nutrition on 10,000 households, using weighed-food records plus inventory methodologies (Saba et al. 1990; Turrini et al. 1991). Three main groups of foods were considered: cereals (pasta, rice, bread and bread products, and pastries), potatoes, legumes. Different commercial brands for each sample were purchased, according to the known presence on the market. Samples were prepared 'as eaten' and submitted to simulated chewing, followed by total and resistant starch determination using the enzymic procedure published as a result of the EC Concerted Action EURESTA (Champ, 1992). From these results, the estimated average intake of RS in Italy was found to be 8.5 g/d, with regional differences (from 7.2 g/d in the north-west to 9.2 g/d in the south) mainly due to the different consumption of some typical Italian starchy food (bread, pasta, legumes).

Gastric emptying of a solid meal is accelerated by the removal of dietary fibre naturally present in food.

Exogenous fibre added to liquid meals delays gastric emptying. Its effect on solid meals is uncertain, and nothing is known of the effect on gastric emptying of fibre naturally present in food. This study therefore looked at gastric emptying of two different solid meals in eight healthy subjects and their blood glucose responses. The meals were exactly equivalent except for the total dietary fibre content (high fibre 20 g, low fibre 4 g of dietary fibre per 1000 kcal) and supplied 870 kcal (700 kcal women), 47% of which was from carbohydrates, 36% from fats, and 17% from proteins. Ultrasonography was used to measure antral diameters before the meal (basal), immediately after it (time 0), and at 30, 60, 120, 180, 240, and 300 minutes. In addition, subjects filled in a questionnaire on their feelings of hunger, epigastric fullness, and satiety before the meal and at hourly intervals after it. Basal and maximal postprandial antral sections were similar for the two meals (basal section: 283.9 (29.5) v 340.9 (44.7) mm2 for the low and the high fibre meal, NS; maximal postprandial section: 1726 (101.9) v 1593 (120.4) mm2, NS). Total gastric emptying time was significantly reduced by fibre removal (186.0 (15.6) v 231.7 (17.3) minutes after the low and the high fibre meal, p < 0.05). Blood glucose was higher after the low fibre meal, and the area under the glycaemic curve significantly greater (226 (23.1) v 160 (20.0) mmol/min/dl-1, p < 0.05). No difference was found in satiety or fullness feelings, but hunger returned more rapidly after the low fibre meal. In conclusion, fibre naturally present in food delays gastric emptying of a solid meal, reduces the glycaemic response, and delays the return of hunger.

Comparison of lactulose and inulin as reference standard for the study of resistant starch fermentation using hydrogen breath test.

Disaccharide lactulose is commonly used as a standard to quantitate the colonic fermentation of undigested sugars by means of H2 breath measurements. However, its high hydrogen production rate during fermentation may make it inappropriate for mimicking the fermentation of more complex carbohydrates, such as starch. Indigestible carbohydrates with a higher molecular weight might be more suitable than lactulose as a standard in H2 breath studies of starch digestibility. To test this hypothesis, we measured H2 breath in 8 healthy volunteers after a standard meal supplemented with 5 g or 10 g of lactulose or inulin, an indigestible oligosaccharide with an average degree of polymerization 4.5 times higher than that of lactulose. The results were then compared with those obtained after a standard meal containing a known amount (6.1 g) of resistant starch from high-amylose corn starch. Median H2 breath excretion per gram of reference carbohydrate was lower after the 5 g dose of inulin than after the 5 g dose of lactulose (19.1 vs 26.6 ppm x h x g-1; Wilcoxon's rank test p = 0.021) but similar after the two 10 g doses (inulin 22.4; lactulose 23.6; p = 0.234). Median H2 breath excretion per gram of resistant starch was significantly lower than that for both lactulose and inulin (p < 0.02), being 4.7 ppm x h x g-1. In vitro fermentation for 8 hrs with fecal homogenate showed similar mean hydrogen production rates for inulin and lactulose (30.5 vs 27.7 mL/mg fermented carbohydrate), and a significantly lower rate for starch (9.1 mL/mg) (n = 7; ANOVA p = 0.0007).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of neutralized and native vinegar on blood glucose and acetate responses to a mixed meal in healthy subjects.

OBJECTIVE: To investigate the influence of sodium acetate and acetic acid from vinegar on blood glucose and acetate response to a mixed meal in healthy subjects. DESIGN: Five healthy subjects consumed in random order six test meals consisting of 100 g of sliced lettuce dressed with olive oil (Blank), olive oil plus 1 g acetic acid in the form of vinegar (AcOH), or olive oil plus sodium acetate in the form of vinegar neutralized to pH 6.0 with sodium bicarbonate (AcNa). On three occasions test meals were followed by a challenge consisting of 50 g carbohydrate portions of white bread (Bread). Glucose and acetate concentrations were measured in arterialized capillary blood before and until 95 min after the meals. Ultrasonography was performed in four other subjects to measure gastric emptying times after AcOH + Bread and AcNa + Bread. RESULTS: Blood acetate response over 95 min was markedly reduced after AcOH and AcOH+Bread meals compared to AcNa and AcNa + Bread. Similarly, the glucose response was depressed by 31.4% (P = 0.0228) after AcOH+Bread with respect to AcNa + Bread and Blank + Bread. No difference was observed between gastric emptying times after AcOH + Bread and AcNa + Bread. CONCLUSIONS: The results suggest that oral acetic acid and acetate might have a different effect on acetataemia and that a limited dose of vinegar, in the form of salad dressing, is sufficient to influence significantly the glycaemic response to a mixed meal in normal subjects by a mechanism related to acidity but not to gastric emptying.

Gastric emptying of solids is markedly delayed when meals are fried.

We studied the effect of heat-treated fats on gastric emptying. Eight healthy asymptomatic volunteers (five males; age 28-41 years) ate on different days and in random order two meals identical in contents (pasta, tomato, beef, olive oil, carrots, orange, water; 870 kcal males, 700 kcal females; 47% of calories from carbohydrate, 36% from fat, 17% from protein), but cooked differently (fats fried or not). Ultrasound measurement of antral diameters was used to calculate basal antral section, its maximal dilation after the meal, the time necessary for total emptying, and the percent retention at hourly intervals. No difference was found in basal and maximal antral diameters after the two meals. On the contrary, total gastric emptying was significantly delayed after the fried meal [317.1 (24.12) vs 226.7 (18.4) min, mean (1 SEM); P < 0.002]. A significantly greater percentage of maximal antral distension was still present between 120 and 240 min after the fried meal. The glycemic response and hunger feeling were the same after the two meals, whereas there was a longer persistence of satiety and epigastric fullness after the fried meal. In conclusion, gastric emptying can be influenced not only by the meal content, but also by the way it is cooked.

Digestibility of carbohydrates from rice-, oat- and wheat-based ready-to-eat breakfast cereals in children.

OBJECTIVE: To study the effect of the presence and quality of dietary fibre in ready-to-eat (RTE) breakfast cereals on completeness of carbohydrate digestion in children and on starch susceptibility to alpha-amylase in vitro. DESIGN: A controlled intervention study. SUBJECTS: Eight 3-8-year-old healthy children. INTERVENTIONS: Completeness of digestion was evaluated by assessing the amount of carbohydrates apparently fermented into the colon using the breath-H2 technique after consumption in random order, of five breakfast tests containing boiled rice (either alone or supplemented with 3 g of lactulose) as reference food, or RTE cereals based on rice (low-fibre), wheat (high insoluble fibre) and oats (high-soluble fibre). The potential glycaemic impact of the products was estimated in vitro by assessing starch susceptibility to alpha-amylolysis using an enzymatic-dialysis method. RESULTS: Compared to boiled rice and to rice-based RTE cereal, wheat- and oat-based RTE cereals both significantly (P < 0.05) increased the amount of apparently fermented carbohydrates (+1.1 +/- 1.7% of total breakfast carbohydrate fermented for rice, +5.6 +/- 0.9% for wheat and +9.4 +/- 3.7% for oats; mean +/- SEM), calculated using the excess H2 in breath after lactulose as standard. All products showed similar in vitro digestibility, resulting in estimated glycaemic indexes of 117.5 (24.0) for rice, and 105.7 (14.1) for oats-based, 128.4 (17.6) for wheat-based, and 129.8 (16.6) [mean 95% CI)] for rice-based RTE cereals. CONCLUSIONS: Results suggest that the presence of fibre in RTE breakfast cereals, in particular soluble fibre, increases colonic fermentation in children whereas it seems not to affect glucose availability.