فصلنامه پژوهش های صنایع غذایی
سال بیستم شماره 2 (تابستان 1389)

Qualitative and quantitative analyses of ‘Zonouz’ and ‘Gala’ apples polyphenolic compounds were carried out by HPLC during the commercial harvest time. The results showed qualitative differences between the two apple cultivars regarding polyphenolic compounds. In general, ‘Gala’ had higher polyphenolic compounds compared to ‘Zonouz’. The highest polyphenolics content was recorded in the Gala's peel and seed. The predominant flavonoids in the Gala's peel were quercetin-3-D-galactoside and cyanidin-3-galactoside with 45.7% and 42.3% of the total identified components, respectively. Phloridzin dihydrate (86.3% of the total flavonoid compounds) contained the principal flavonoid compound in the Gala's seed. Cyanidin-3-galactoside and (-)-epicatechin were the main flavonoid compounds in the Zonouz's peel with 65.4 and 26.1% of the total flavonoids. Phloridzin dihydrate (82.6% of the total flavonoids) was the major flavonoid compound in the Zonouz's seeds. The Zonouz's Peel and pulp had higher flavonoid and phenolic acids content compared to Gala. Chlorogenic acid (1mg/g DW) and (-)-epicatechin (0.5mg/g DW) were the highest phenolic acid and flavonoid components in the Zonouz's peel and pulp, respectively. Rutin hydrate was another major flavonoid constituent of Zonouz's pulp with 5.8% of the total identified flavonoids. This compound was absent in the Gala's pulp. Caffeic acid content in the Zonouz's pulp (0.3 mg/g DW) was considerably higher than Gala (0.08 mg/g DW).

In this study a two-step approach was applied in order to investigate the effect of seven factors including: concentration of ammonium sulphate، potassium dihydrogen phosphate، date pulp، pH، inoculums size، agitation speed and fermentation time on the pectinlyase production by Aspergillus niger. At first step، the effects of these variables were studied using fractional factorial design. According to obtained results three factors، pH، ammonium sulphate concentration and fermentation time were considered for further study. Second step was carried out by using central composite design (CCD) in order to find optimum conditions of pH، ammonium sulphate concentration and fermentation time. After analysis of CCD، optimum condition for maximization of pectinlyase activity determined as follow: ammonium sulphate concentration 0. 35%، fermentation time، 73. 93 hours and pH، 4. 82. Enzyme activity at this optimum condition was 1. 38 U. ml -1.

Enzymatic browning is one of the most important problems in fresh-cut products preparation and storage of fruits. A research was conducted using CaCl2 (at concentrations of 0 and 1%) and ascorbic acid (at concentrations of 0، 0. 5 and 1%) in order to prevent enzymatic browning and maintain attributes of fresh-cut ‘Golden Delicious’ apples. The control fruits were treated with distilled water. After treatments، the fresh-cut fruits were packed and stored at 2. 5 C with 90-95% RH for 14 days. The fruits were subjected to quality assessments at the first day and after 7 and 14 days of cold storage. The results indicated that both treatments significantly prevented enzymatic browning. Also the treatments significantly affected fruits total phenolics and vitamin C content but had no effect on total soluble solid content. The combination treatment of ascorbic acid and CaCl2 had a significant effect on the titratable acidity.

Apple samples (Golden delicious variety) were harvested at 5 different times at one-week intervals from September 17 to October 15. To evaluate the texture changes during three months storage in a cold room at 0 C and 95% RH، chemical and textural analyses were carried out. In chemical analysis، acidity، soluble solids (Brix)، total sugar and reducing sugar were determined. The samples were cut into two halves and texture analysis was performed on the halves in the form of “with and without skin”. Force-deformation curves were obtained by carrying out uniaxial penetration and compression tests. Crispness، fracturability of the skin and hardness of the flesh، total firmness، toughness and modulus of elasticity were calculated and compared using the curves. The results showed that during the storage time، acidity decreased and Brix، total sugar and reducing sugar increased. The mechanical properties were decreased by increasing storage time. The smallest changes on the fracturability of the skin and hardness of the flesh and modulus of elasticity were generally observed for samples harvested before full maturation.

Temperature profile and moisture concentration during the cheese salting process play an important role in cheese quality since the microbial and enzyme activities، are affected by them. In this work، a one dimensional heat transfer model was developed in the ultrafilterated cheese by using the numerical solution of the Fourier second law with finite difference method (Crank- Nicholson scheme) as a function of internal (cheese chemical composition at any point) and external variables (temperature and air velocity of storage). The comparison of the experimental and predicted temperature values using MATLAB showed a good agreement between the model and the experimental data (R2 > 99).

Effects of putrescine and nitric oxide on the quality attributes and postharvest life of the table grape (cv. Sefide bidane) were investigated. Fruits were treated with nitric oxide (at 0، 3، 5 and 7 µmol L-1) and putrescine)at 0، 1 and 2 mmol L-1) and stored at 0-1oC with 85-95% RH for 3 months. Fruit quality attributes including weight loss، pH، decay incidence، total acidity، vitamin C، total soluble solids and total phenolics were evaluated after 3 months. Both nitric oxide and putrescine significantly decreased fruit postharvest decays (at the 5% and 1% probability levels). The results showed that 5 µmol L-1 nitric oxide and 2 mmol L-1 putrescine effectively controlled decayed organisms and preserved fruit quality during cold storage. Both phenolics and pH were affected by NO and putrescine treatments. It was concluded that postharvest treatment of fruit with the combination of nitric oxide and putrescine is a good alternative to chemicals in postharvest technology of table grapes.

Traditional microeconomics theory that is constrained on the perfect competition assumes that price is pre-anticipated، but the thing happens most of the times in real market is that the price changes according to the demand. This situation happens usually in the agriculture market and considered as the Cobweb Curves. As production is supplied in the market، the price reacts to adjust the market. In this contest، the inverse demand functions are used to investigate the response of price according to the quantity supplied. To address this، we used the Inverse Almost Ideal Demand System (IAIDS) for 8 major articles of food from the year 1353 to 1386 under different scenarios to forecast the prices. The results showed that the most self-quantity elasticity is related to meat (-1. 04) and the least one is for milk (-0. 77). Also، the result of quantity variation on the prices according to different scenarios indicated that if the quantity of the different food articles in the market decreases (increases)، their prices will increases (decreases). The results differ in various groups and its intensity is dependent on the quantity elasticity and scale elasticity of each article group of food.

Celiac disease is a lifelong intolerance to some cereal prolamins. The gliadin fraction of wheat، secalins of rye، hordenins of barley، and avenins of oats are involved in the Celiac disease mechanism. The only effective treatment for such symptom is strict adherence to a gluten-free diet throughout the patient’s lifetime. Gluten free breads require polymeric substances that mimic the viscoelastic properties of gluten to provide structure and retain gas. Concerning the fact that gluten-free breads are not commercially produced in Iran، this study aims to find a proper gluten free bread formulation using different hydrocolloids. Therefore، pectin، guar and carrageenan as most commonly used hydrocolloids in the formulation of gluten free breads were applied in concentration of 1، 2 and 3%. Moreover، the effect of combination of those hydrocolloids in concentrations of 2 and 3% was studied on bread quality characteristics (loaf volume، specific volume and loaf height). Results showed that control bread (wheat starch without hydrocolloid) induced the least loaf volume and height. All hydrocolloids، except carrageenan caused a significant (α<0. 05) increase in bread loaf volume and height. Gluten free breads made from pectin (in concentration of 3%) and guar-pectin (in concentration of 2 and 3%) showed the highest loaf volume and height compared those prepared from other hydrocolloids. Hydrocolloids in gluten free breads formulation play as polymeric substances، in which they swell more easily and form a continuous phase similar to those structures of gluten network in wheat flour dough. Concluding، some hydrocolloids mimic the viscoelastic properties of gluten in the bread dough.

Natural fermentation based on the inherent flour microflora is an ancient sourdough making process. Nowadays، selected starter cultures are used to provide quality consistency in the sourdough making process. In this study، the effects of two-stage or sponge-and-dough process using L. reuteri starter culture versus single-stage or straight dough processes on the properties of resulting dough and bread were assessed. In general، the sponge-and dough process led to lower pH and higher total titrable acidity in the resulting dough. The straight dough process resulted in breads with significantly higher pH and lower total titrable acidity than those of sponge-and-dough process. Loaf volume and bread height was increased when straight dough method was applied. However، bread moisture content remained higher for sponge-and dough process. There was no significant difference between sensory scores of breads prepared from both dough making processes. Nevertheless، sponge-and-dough process resulted in softer breads with low staling rate. Moreover، sponge-and-dough breads showed better shelf life with delayed mold growth.

In recent years، apple core rot have frequently been observed in East and West Azarbaijan provinces، Iran. As apple plays a major role in food industry، in present study fungal groups involved in apple core rot disease were elucidated by means of morphology and DNA sequence data. Apple fruits were purchased from local market in Tabriz، Khoy، Shabestar، Sofiyan، Talesh، Miyandoab and Jolfa cities. Small pieces from core tissues of apple fruits were surface-sterilized and plated on malt extract agar medium. Isolated fungi were purified and then identified using morphological and DNA sequence data. For molecular evaluation، DNA extraction carried out on pure cultures of selected fungal isolates and ITS region of ribosomal DNA (ITS-rDNA) was amplified and sequenced. In total، from the 30 isolates evaluated in this study، Alternaria and Penicillium species with 13 and 9 isolates were the most prevalent fungal groups. The other fungal groups were identified as Cladosporium spp.، Tricothecium sp.، Acremonium sp. and Stemphylium sp. Most of the fungal groups isolated in this study are toxicogenic; however، the main focus has been on the mycotoxin produced by Penicillium and Aspergillus in apple products، so far. The results of this study urge awareness on the possible contamination of apple fruit and its products by Alternaria toxins.

Despite of beneficial effects of antibiotics in treatments of infectious diseases, antibiotic residues in milk, meat and their products can cause serious side effects for human health. The objective of this study was to monitor antibiotics residues in raw and pasteurised milk produced in Eastern Azerbaijan province of Iran. For this purpose, 10 industrial dairy farms as well as 10 local milk collection centers and 6 dairy processing plants were randomly selected. Raw milk samples were collected in 5 and pasteurised milk samples in 10 replications. Residual antibiotic of milk samples were monitored by Delvotest (version SP) kits. The results showed that 26% of raw milk samples collected from industrial dairies and 16% of raw milk of collection centers showed detectible antibiotic residues. In addition, 30% of pasteurised milk samples showed positive Delvotest results. Concluding, the antibiotic residue in milk and dairy products has to be monitored as routine test due to their side effects on human health.

In order to investigate the viscoelastic properties of Thompson seedless grapes in ripening، relaxation tests were carried out on whole berry، flesh and skin of the fruit. Samples were harvested weekly from a grapevine for seven consecutive weeks and relaxation test was done using a texture analyzer after sample preparation. The first term of generalized Maxwell model with three elements was determined using a series of assumed data and then the experimental data were evaluated by the model. The results showed that the magnitude of initial stress (stress at time zero) required to create a fixed strain on whole fruit decreases during ripening period when ºBrix of the fruit increases from 16. 0±0. 45 to 22. 5±0. 25، but the relaxation time remains almost constant at the range of 41. 681 to 45. 630 s. Based on results، elastic behavior of the skin enhances and firmness of flesh increases during fruit growth and ripening. According to the results، the skin as compared with the flesh plays a main role on the behavior of viscoelastic alterations of whole fruit. Also on the basis of results obtained by non-linear regression analysis، amount of elastic components of the model raises for flesh and declines for skin and whole berry through ripening. The generalized Maxwell with three elements was the best in fitting experimental data with highest determination coefficients.