In vitro amylolytic degradation of natural and graft copolymerised cassava and potato starches

 Various enzymatic hydrolyses to maximise degradation of the starch moiety of grafted starch (starch–g-polyacrylonitrile) were tried. The percentage of α- and β-amylolyses of grafted starch were 55 and 50 compared to 80 and 70 respectively for natural starches. Sequential degradation with α-amylase and glucoamylase of grafted starch showed 70% hydrolysis. The maltooligosaccharide profile by HPLC of the hydrolysates of grafted starch showed oligomers up to a degree of polymerisation (DP) 3, whereas the natural starch hydrolysates showed up to DP 7. The percentage hydrolysis, as well as the enzyme degradation profile, remained similar for both potato and cassava starches. Further treatment of the grafted starch hydrolysates with Bacillus cereus cells showed the presence of very low molecular weight polyacrylonitrile chains grafted onto maltooligosaccharides. The size exclusion chromatography analysis of grafted starch indicated the amylose component of starch that undergoes graft copolymerisation. Received: 30 December 1999     

Comparative study of the physicochemical and palynological characteristics of honey from Melipona subnitida and Apis mellifera

Twenty‐four samples of Apis mellifera honey and twenty‐four samples of Melipona subnitida (Jandaira) honey were collected in the northeast of Brazil. Moisture, hydroxymethylfurfural, free acidity, insoluble solids in water, diastase activity, ashes, electrical conductivity, proteins, lipids, total carbohydrates, energy and sugars were the parameters analysed. The efficiency of the qualitative tests (Fiehe's test, Lugol's reaction, Lund's reaction) was tested. Pollen types and the corresponding plant species were identified in all samples (3 in Apis and 1 in Melipona). Apis mellifera honey samples demonstrated parameters in accordance with the Brazilian Legislation, while the Melipona subnitida honey samples displayed moisture (24.80%) and diastase activity (null) in discordance with the established by the regulation for Apis mellifera honeys. Apis honey samples presented higher values of electric conductivity (284.00 μS cm^?1) than the obtained from the Jandaira honey samples (102.77 μS cm^?1) as well as a darker colour (26.67 mmPfund) when compared with Jandaira honey (7.00 mmPfund). The concentration of the glucose, fructose and sucrose was higher in the Apis honeys than in the Jandaira honey. The characteristics of the two types of honey were very different, highlighting the need of developing specific legislation for stingless bees' honey.     

Structural studies of resistant starch derived from processed (autoclaved) rice

 Resistant starch (RS), isolated by hydrolysis with Termamyl, protease and amyloglucosidase, of five-cycle autoclaved rice was purified by size exclusion chromatography. Structural characterization by β-amylolysis, ¹³C NMR and methylation followed by GC-MS analysis revealed RS to be a linear (1→4)-α-d-glucan, originating probably from amylose. Its molecular weight was low, 1.20×10⁶ Da, and amounted to 7400 d-glucose residues. X-ray diffraction measurements showed RS to have both B-type and V-type diffraction patterns. Differential scanning calorimetry data revealed the thermal stability characteristics of RS. The undigested material (equivalent to RS) recovered from the ileum of rat intestine exhibited an almost comparable GPC profile, molecular weight and λ_max characteristics with those of in vitro isolated RS. Received: 7 September 1998     

Indigestible fraction of okara from soybean: composition,physicochemical properties and in vitro fermentability by pure cultures of <Emphasis Type="Italic">Lactobacillus acidophilus</Emphasis> and <Emphasis Type="Italic">Bifidobacterium bifidum</Emphasis>

Major non-digestible components of soybean seeds and okara were determined by an in vitro enzymatic-physiological method, alternative to dietary fibre. Total indigestible fraction was higher in okara (41.6%) than in seeds (28.5%), and consisted of soluble and insoluble fractions, mainly composed of non-starch polysaccharides, klason lignin and resistant protein. Total protein was lower in okara (32.29%) than in seeds (46.97%), as were oil (14.72% okara–20.89% seeds) and ash contents (3.18% okara–4.60% seeds). In vitro digestibility of protein was lower for okara (84.3%), than for soybean seed (91.8%). Moreover, okara showed high swelling (10.54 ± 0.14 mL/g d.w.) and water retention capacity (8.87 ± 0.06 g/g d.w.) and was fermented in vitro to a greater extent by Bifidobacterium bifidum (29.8%), than by Lactobacillus acidophilus (8.3%). For its composition, physico-chemical properties and bifidogenic capacity in vitro, okara is a potential candidate to be a prebiotic fibre-rich ingredient of new functional foods. An erratum to this article can be found at     

Cold storage of apples (cv. Granny Smith) and changes in phenolic compounds

 The Granny Smith variety of apple behaves differently to other apple cultivars, in that it needs an abnormally long time to ripen at room temperature. Its maturation has been accelerated by low-temperature stress. Fruit collected at commercial maturity were chosen and submitted to storage at 4 °C for 10 days and rewarming at 22 °C, to assay the influence of cold storage on their content of phenolic compounds. The behaviour of phenolic compounds was different in peel and in pulp. In the pulp, apple phenolic compounds decreased during the development period and during the cold treatment. In the peel, the quantity of phenolic compounds increased with time after the cold treatment, reversing their normal behaviour during the development period. Received: 11 March 1996     

An introduction: Evolution and finalisation of the regulatory definition of dietary fibre

It is more than 56 years since Hipsley (1953) first used the term dietary fibre for the non-digestible constituents of plant cell walls and more than 30 years since 14 and 13 adopted the term and suggested a definition for “dietary fibre”. Since this time there has been no accepted international regulatory definition until Codex adopted a final definition in its 2009 meeting. The sequence of these protracted discussions and consequential evolving views about dietary fibre regulatory definitions are here reviewed.     

Identification of key aroma compounds generated from cysteine and carbohydrates under roasting conditions

 Application of the aroma extract dilution analysis to volatile fractions obtained from dry-heated (180  °C for 6 min on silica) mixtures of cysteine and ribose (I), glucose (II) or rhamnose (III) revealed the following compounds with the highest flavour dilution factors: 2-furfurylthiol (FFT) and 2-acetyl-2-thiazoline in I; 2-acetyl-2-thiazoline, 2-propionyl-2-thiazoline and FFT in II; 5-methyl-2-furfurylthiol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 2-acetyl-2-thiazoline, 2-propionyl-2-thiazoline and (Z)-2-propenyl-3,5-dimethylpyrazine in III. A comparison of the data with results of previous studies, in which the same mixtures had been reacted under aqueous conditions (145  °C, 20 min) revealed that the dry-heating process favoured the formation of the roasty, popcorn-like smelling 2-acetyl- and 2-propionyl-2-thiazoline as well as the potato-chip-like 2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine in all three reaction systems. 2-Ethenyl- and (Z)-2-propenyl-3,5-dimethylpyrazine, both having an intense roast potato smell were, however, selectively formed in the presence of ribose or rhamnose, respectively. Based on quantitative data, pathways generating the latter two pyrazines via their 1-desoxyosones as key intermediates are discussed. Received: 11 March 1998     

Flavour and off-flavour compounds of black and white pepper (Piper nigrum L.) I. Evaluation of potent odorants of black pepper by dilution and concentration techniques

 Dilution and concentration experiments as well as enantioselective analysis of optically active monoterpenes indicated (±)-linalool, (+)-α-phellandrene, (–)-limonene, myrcene, (–)-α-pinene, 3-methylbutanal and methylpropanal as the most potent odorants of black pepper. Additionally, 2-isopropyl-3-methoxypyrazine and 2,3-diethyl-5-methylpyrazine were detected as important odorants of a black pepper sample with a mouldy, musty off-flavour. Received: 24 September 1998     

Optimisation of the extraction of phenolic compounds and antioxidant activity from aerial parts of Bidens pilosa L. using response surface methodology

Response surface methodology was used to find the optimum ethanol concentration and temperature which maximises the antioxidant activity (AA) of hydroalcoholic extracts from aerial parts of Bidens pilosa L. A rotatable central composite design was used, and the extracts were characterised by the determination of solid concentration (SC), total flavonoid (TFC) and total polyphenol content (TPC). AA was determined through 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulphonic acid) diammonium salt (ABTS) and 2,2‐diphenyl‐1‐pycrylhydrazyl (DPPH) radical scavenging activity. Mathematical models showed the significant effects of each variable and allowed to select the optimum conditions of ethanol concentration (62.7%) and extraction temperature (66.2 °C). The optimised extract presented an AA of 804.9 ± 12.2 Trolox equivalent antioxidant capacity (TEAC) dry base (d.b.) for DPPH and 515.8 ± 31.8 TEAC d.b. for ABTS. It was observed that both TFC and TPC showed a good correlation with AA of the extracts.