Quality Of Yogurt Research Articles

Evaluation of Rabbit Skin Gelatin and Preparation of Yogurt using Rabbit Skin Gelatin

TThe purpose of this research is to know the quality of rabbit skin gelatin soaked in the concentration of different acetic acid as well as its application in yogurt making. Compared to the use of the Arab Gum and CMC (Carboxymethyl Cellulose) The material used in this study was the rabbit skin type Rex male. The treatment of this research is the immersion of acetic acid with 2 %; 3 %; 4 %; 5 % concentration. The results showed that concentrations of acetic acid solution in the process of soaking of acid extract gave a very significant effect (p < 0.01) toward yield, pH, protein, fat, viscosity, gel strength, the melting point of rabbit skin gelatin. Application of rabbit skin gelatin on yogurt making gives better yogurt quality compared with the addition of Arabic Gum or CMC. The results showed that the various stabilizers in the yogurt-making process give significant effect (p < 0.01) to the resulting pH, The power of the water belt, Synergized, Viscosities of yogurt. However, the various stabilizers in the yogurt-making process give a non-significant effect (p > 0.05) to the resulting acidity of yogurt. The conclusion to immersion acetic acid with a concentration of up to 5% will improve the quality of the rabbit skin gelatin and the use of rabbit skin gelatin by 0.8 % as a stabilizer in the manufacture of yogurt produces a better-quality yogurt compared to the Arabic Gum and CMC (Carboxymethyl Cellulose).

HOME / ARCHIVES / VOL. 9 NO. 6 (2021): EUROPEAN JOURNAL OF APPLIED SCIENCES / Articles Isolation and Molecular Characterization of Legume Microorganisms Used in Yogurt FermentationYogurt is generally defined as a fermented dairy product which is produced by using the symbiotic cultures of Streptococcus thermophilus and Lactobacillus delbrue

Yogurt is generally defined as a fermented dairy product which is produced by using the symbiotic cultures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.  The positive effects of yogurt and other similar fermented dairy products on human diet and health continue to be proven and this has led to increased yogurt consumption in the world which in turn demands more production. In addition, there are works in progress to improve yogurt quality and produce yogurt with various specifications using newly developed techniques. In this study, four distinct types of legume (lentil, bean, cow pea and broad bean) were used to ferment yogurt from milk of without UHT. Yogurt samples were diluted and then each sample was transferred to a M17 Agar medium and bacteria were isolated from these samples. Fresh pure cultures were obtained. The new generation sequence was subjected to a 16s rRNA array analysis and characterization using MALDI-TOF methods. It was determined that the bacteria in the yogurt which were produced were Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. In accordance with the data obtained, the bacteria which was reproduced in the MRS and M17 mediums proved to be preliminary examples of cultivated bacteria which can be utilized in commercial yogurt production.

Potential of brewers’ spent grain in yogurt fermentation and evaluation of its impact in rheological behaviour, consistency, microstructural properties and acidity profile during the refrigerated storage

Brewers’ spent grain (BSG) contains high amounts of dietary fiber, which may regulate the food matrix behaviour. The study aimed to evaluate the impact of spent grain on yogurt. Different levels of BSG were substituted in yogurt fermentation and its impacts on microstructural properties including surface chemical properties and confocal microstructures were studied. The quality of the yogurt was evaluated by determining rheological behavior, syneresis, color, acidity and the amount of lactic acid bacteria (LAB) at 1, 7 and 14 days of storage. The addition of BSG shortened the fermentation time, increased the viscosity and shear stress. FTIR analysis showed that BSG intensifies the band region stretching which describes a modification in a certain functional group. Confocal laser scanning microscopy identified a disruption in the cross-link between fat-protein and yogurt matrix due to the addition of BSG. During the storage, BSG was able to maintain the flow behaviour and stability, which was shown as the change in flow behaviour and syneresis. Furthermore, BSG provided the nutrients for the survival of LAB during the storage and maintained the amount of lactic acid in yogurt during the 14 days of refrigerated storage. The substitution 5%–10% of BSG improved the quality of yogurt as the maximum quality such as acidity, rheological behavior and LAB growth. Even though 15%–20% of BSG generated the same level of acidity and LAB, and had the lowest syneresis, it diminished the flow performance of the yogurt.

Effects of thermally treated mulberry leaves on the quality, properties, and antioxidant activities of yogurt

Effects of thermally treated mulberry leaves on the quality, properties, and antioxidant activities of yogurt

Inhibition of Advanced Glycation End Products in Yogurt by Lotus Seedpod Oligomeric Procyanidin.

The basic ingredients of yogurt include lactose and protein. Yogurt undergoes the Maillard reaction easily, producing many advanced glycation end products (AGEs) that cause some chronic diseases. Lotus seedpod oligomeric procyanidin (LSOPC) have demonstrated a strong inhibitory effect on AGE formation in simulated models; however, the inhibition of procyanidin on AGE formation and the subsequent effects on yogurt quality remains unknown. Our study demonstrated that LSOPC had a good inhibitory effect on the formation of fluorescent AGEs and Nε-carboxymethyl lysine (P < 0.05). The inhibitory capacity on AGEs and antioxidant activity of yogurt were positively correlated with the concentration of LSOPC. The effect of LSOPC on the physicochemical properties of yogurt was also evaluated. Bound water content, viscosity, and flavor of yogurt were significantly increased after LSOPC addition (P < 0.05). Therefore, LSOPC may lead to significant benefits for controlling AGE formation and improving the quality of yogurt.

Study of Making Yogurt From Peanut (Arachis hypogaea L.) With The Addition of Coconut Water and Skim Milk

Abstract- Plant-based functional foods has been highly developed in recent years. Peanut (Arachis hypogaea L.) can be used as functional drink that substitute for cow's milk. This study aimed to determine the effect of ratio (peanut milk and coconut water) and skim milk concentration on the quality of peanut yogurt. Yogurt was made by mixing peanut milk with coconut water and adding skim milk. The ratio of peanut milk and coconut water (50% : 50% and 75% : 25% v/v) and skim milk concentration (0%, 1% and 2% w/v). Fermentation was carried out at room temperature for 12 hours using commercial yogurt starter culture. Peanut yogurt analysis included of total LAB, pH, total acid and organoleptic. The data obtained were tabulated and presented descriptively. The best peanut yogurt was obtained in the ratio of peanut milk and coconut water (75%: 25%) and the addition of 2% skim milk which showed total LAB, pH and total acid were 9.2 x 109 CFU/mL, 2.8 and 0.37% respectively.

Yogurt As A Functional Drink Development From Various Local Raw Materials Using Eucheuma Spinosum As Natural Stabilizer

Along with raising public awareness about health and increasing yogurt consumption, it is critical to improve the quality of the yogurt. The innovation of yogurt producing in terms of flavor variety is critical since it can entice consumers to consume yogurt. This innovation is possible through the use of high-nutrient plant components that have not been optimally exploited in the surrounding environment. The purpose of this study was to examine the quality of yogurt produced from a variety of raw materials and stabilized naturally using Eucheuma spinosum seaweed. This study used a completely randomized design with a single factor: the type of raw material utilized in the production of yogurt (corn, sweet potato, pumpkin, banana and pineapple). The parameters analyzed included total lactic acid content, pH, total lactic acid bacteria, bacterial viability, viscosity, and organoleptic qualities such as homogeneity and taste were examined using scoring and hedonic methods. The data were evaluated using an analysis of variance (ANOVA) with a significance level of 5%, and the significantly different data were further tested using an additional test of an honest significant difference (HSD). Results show that yogurt made from corn was the best treatment, with pH value of 4.28, total lactic acid content was 1.67%; viscosity was 74,67cP, total lactic acid bacteria was 11.02 log CFU/ml, the bacterial viability met the concentration as a probiotic drink with the decreasing number 0.21 log CFU/ml, scoring test homogeneity score was 3,21 (slightly homogenous), taste score was 3.08 (slightly sour) and hedonic score for homogeneity and taste were 3.29 and 3.25 respectively.

Microstructural, Volatile Compounds, Microbiological and Organoleptical Characteristics of Low-Fat Buffalo Milk Yogurt Enriched with Whey Protein Concentrate and Ca-Caseinate during Cold Storage

Yogurt is a popular fermented milk product across the world. Structure, taste, and odor characteristics are created by fermenting yogurt with diverse ingredients and lactic acid bacteria (LAB), which contribute the most to the acceptance and quality of yogurt. In this study, low-fat buffalo milk yogurts (LFBY) were produced with the enrichment of 1% (w/w) whey protein concentrate (WPC) and Ca-caseinate (Ca-CN). Yogurts were analyzed based on microstructural, microbiological, organoleptical properties; volatile compounds (solid-phase microextraction method associated with gas chromatography-mass spectrometry) during cold storage for 21 days. Yogurts enriched with WPC and Ca-CN had higher total solids, total protein contents, and pH values. A total of 36 volatile components were identified in all produced yogurts. Acetic acid, butanoic acid, acetaldehyde, acetoin, 2,3-butanedione, ethanol, and 1-heptanol were found in significant amounts and mainly contributed to organoleptical properties. Interestingly, the focused volatile compounds that improve taste and odor were higher in LFBY+WPC yogurt than in plain LFBY or LFBY+Ca-CN yogurt. The Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus viable counts were higher in LFBY+WPC yogurt than plain LFBY or/and LFBY+Ca-CN. Conclusively, yogurt enriched with 1% WPC exhibited the best organoleptical properties and volatile component concentrations. The microstructure of the LFBY with WPC was less compact and dense, and regular, with tiny pores and long and individualized casein filaments than the other treatments. The microstructure of the Ca-CN samples caused a compact structure and coarse than in the control yogurt.

Effect of Supercritical Extract from Black Poplar and Basket Willow on the Quality of Natural and Probiotic Drinkable Yogurt.

Simple SummaryFermented milk products should be an important component of the human diet due to their high nutritional value and easy digestibility. In order to enhance the nutritional value of yogurts, additives in the form of plant-based raw materials are often used. Phytoextracts are a mixture of biologically active compounds that can have beneficial effects on the human body and influence both the manufacturing process and the quality of food products. The incorporation of extracts from the basket willow (Salix viminalis) into natural and probiotic yogurts reduced the fermentation time and increased their antioxidant activity. Sensory evaluation of the appearance and texture of yogurts enriched with extracts showed no significant differences compared to natural yogurts. The addition of plant extracts may enable the standardisation of yogurt quality and increase its biological activity.Yogurt is a fermented milk drink produced by Streptococcus thermophilus, Lactobacillus delbrüeckii ssp. bulgaricus, or Lactobacillus rhamnosus, which can be enriched with polyphenolic compounds to enhance its antioxidant properties. Supercritical (scCO2/H2O) extracts obtained from the mixture of bark and wood of black poplar (Populus nigra) and basket willow (Salix viminalis) are the source of bioactive compounds. The aim of the study was to assess the effect of supercritical extracts from the P. nigra and S. viminalis on the fermentation, quality, and bioactive properties of drinkable natural and probiotic yogurts. The incorporation of scCO2/H2O extracts at a dose of 0.01% (w/v) into milk for the production of natural and probiotic yogurts increases their functional properties by enhancing the antioxidant activity without causing negative effects on the physicochemical and organoleptic properties of products. The antioxidant activity of yogurt with scCO2/H2O extract from P. nigra and S. viminalis was higher than control yogurts by 1.3–13.2% and 4.4–37.5%, respectively. The addition of a supercritical S. viminalis extract reduced the time of natural and probiotic yogurt fermentation. Natural and probiotic yogurt with scCO2/H2O extracts added was characterised by a bacterial population size of over 7 log cfu/g, and the microflora was active throughout the cold storage period. FTIR analysis confirmed the presence of scCO2/H2O extracts from P. nigra or S. viminalis in both types of yogurt. A secondary structure analysis confirmed interactions between compounds of scCO2/H2O extract from P. nigra and S. viminalis extract with milk proteins. These interactions affect the compounds’ structural and functional properties by changing, e.g., their digestibility and antioxidant properties.

Effect of pea milk preparation on the quality of non-dairy yoghurts

Neutral pea milk was prepared from direct soaking and blending of yellow peas by fresh water at 25 °C (Neu). Four different methods, including alkali water soaking at 25 °C (Alk), dry dehulling and alkali water soaking (Deh + Alk), boiling water blanching, wet dehulling and alkali water soaking (Bla + Alk), as well as boiling water blanching-dehulling and acid water soaking (Bla + Acid) were designed to treat peas. Pea milks were prepared by blending of the treated peas with water at 25 °C followed by centrifugation to remove solid residue. Using pea milk Neu as a reference, the properties and lactic acid bacteria fermentation features of pea milks as affected by pea treatment methods were investigated. Pea treatments resulted in changes in the contents and compositions of proteins, legumin/vicilin ratios, TCA-soluble nitrogen and volatile flavor components of pea milks. Compared with Neu, pea yoghurts prepared from Alk, Deh + Alk and Bla + Alk showed prominent improvements in gel hardness while pea yoghurt from Bla + Acid gave better flavor than others through volatile components analysis and sensory evaluations. On the other hand, different treatment decreased acid formation yield during lactic acid fermentation of pea milks.

Effect of normal and strict anaerobic fermentation on physicochemical quality and metabolomics of yogurt

Generally, yogurts on the market are usually anaerobic fermentation, but oxygen can be still dissolved in the production process, which is actually not strict anaerobic. This study explored the multiple quality indicators and the metabolomic analysis of yogurts fermented by Lactobacillus bulgaricus and Streptococcus thermophilus using two fermentation methods, namely, strict anaerobic and normal fermentation. The changes in flavor substances in yogurts, including 17 free amino acids, 17 fatty acids, and 7 response value, were detected using principal component and multi factor analyses. Based on the results of the comparisons between basic physical and chemical indicators, strict anaerobic fermentation increased the growth and acidification of the two bacteria, the response value of sourness, umami and richness. Strict anaerobic fermentation increased the free amino acid (Fold change = 1.53) and short chain fatty acid levels (Fold change = 1.73), and reduced the polyunsaturated fatty acid (Fold change = 0.51) levels. Furthermore, metabolomic analysis based on UPLC-Triple TOF-MS/MS showed that 92 differential metabolites were screened; 45 differential metabolites were increased and 47 were decreased. The results revealed that strict anaerobic fermentation was beneficial to metabolic changes and nutritional indicators of yogurt, which may be as indicators of valuable reference to improve dairy fermentation process.

Optimization of Fermentation Process and Evaluation of Quality and Flavor of Quinoa Yogurt Produced by Mixed Lactic Acid Bacteria

In this study, Streptococcus thermophilus 6063, Lactobacillus bulgaricus 6064 and Bifidobacterium animalis B15 were selected to ferment quinoa yogurt, and the puffed quinoa powder and milk were used as raw materials. Fermentation process was optimized by orthogonal experiment on the basis of single-factor experiments. And the effects of puffed quinoa powder on quality and flavor of yogurt were also evaluated. Results indicated that the optimal fermentation conditions were as follows: Streptococcus thermophilus: Lactobacillus bulgaricus: Bifidobacterium animalis=2:1:2, inoculation amount 2%(v/v), quinoa powder 5%(w/v) and fermentation temperature 41 ℃. Under these conditions, quinoa yogurt had good flavor, and the total viable number of lactic acid bacteria reached 109 CFU/mL. From the beginning of fermentation to the end of storage for 21 days, the titratable acidity of quinoa yogurt was always higher than that of plain yogurt, but the total number of viable lactic acid bacteria was opposite trend. Compared with plain yogurt, the contents of protein, polyphenols and flavonoids in quinoa yogurt increased respectively by 88.67%, 166.67%, and 284.62%. The contents of lactic acid, formic acid, acetic acid and pyruvate in quinoa yogurt were 5.80, 1.42, 0.11 and 0.01 mg/g, respectively. 74 kinds of volatile substances were detected in quinoa yogurt by GC-MS. Compared with pure yogurt, 30 kinds of new volatile substances were discovered. The research results would provide a technology support for further research and new product development of quinoa yogurt, promoting the application and development of quinoa.

High level expression of a xyloglucanase from Rhizomucor miehei in Pichia pastoris for production of xyloglucan oligosaccharides and its application in yoghurt

The xyloglucanase gene (RmXEG12A) from Rhizomucor miehei CAU432 was successfully expressed in Pichia pastoris. The highest xyloglucanase activity of 25,700 U mL−1 was secreted using high cell density fermentation. RmXEG12A was optimally active at pH 7.0 and 65 °C, respectively. The xyloglucanase exhibited the highest specific activity towards xyloglucan (7915.5 U mg−1). RmXEG12A was subjected to hydrolyze tamarind powder to produce xyloglucan oligosaccharides with the degree of polymerization (DP) 7–9. The hydrolysis ratio of xyloglucan in tamarind powder was 89.8%. Moreover, xyloglucan oligosaccharides (2.0%, w/w) improved the water holding capacity (WHC) of yoghurt by 1.1-fold and promoted the growth of Lactobacillus bulgaricus and Streptococcus thermophiles by 2.3 and 1.6-fold, respectively. Therefore, a suitable xyloglucanase for tamarind powder hydrolysis was expressed in P. pastoris at high level and xyloglucan oligosaccharides improved the quality of yoghurt.

Improvement in fermentation process and curd quality of yoghurt made from antimicrobial drug added milk

Improvement in fermentation process and curd quality of yoghurt made from antimicrobial drug added milk

Non-Fat Yogurt Fortified with Whey Protein Isolate: Physicochemical, Rheological, and Microstructural Properties.

The demand for low- and non-fat products has recently increased due to the health problems, such as obesity, diabetes, and cardiovascular diseases, that have resulted from high-fat products. However, the reduction in fat can affect the quality of products adversely. The objective of this work was to explore the potential of whey protein isolate (WPI) in improving the quality of non-fat yogurt prepared using skim milk powder (SMP). Yogurt mixes (standardized at 14% total solids) were formulated using SMP as a milk base enriched with WPI. The SMP was replaced by WPI in the yogurt mixes at a rate of 3, 5, 7, and 9%. Full-fat and non-fat set-style yogurts were prepared from whole milk and skim milk, respectively, as controls. Yogurts were fermented at 43 °C to get a pH of 4.6 and stored at 4 °C for the next day. The texture, microstructure, rheological characteristics, and sensory properties of the yogurt samples were studied. The incorporation of WPI increased the water holding capacity to 50% as compared to the non-fat control. This improved the rheological properties while the yogurt viscosity increased in direct proportion with increasing the WPI. The firmness of yogurt was inversely proportional to the increase in WPI, which resulted in 180 g firmness when 9% WPI was added to the non-fat yogurt formulations. Yogurts’ microstructure improved by the addition of WPI. The non-fat yogurt incorporated with 3 and 7% WPI had comparable sensory and textural characteristics to the full-fat yogurt. WPI can be used as a fat replacer to develop low-fat yogurt with desired features. WPI may be a natural and economical ingredient for producing low- and non-fat fermented dairy food products.

Impact of sea buckthorn berries (Hippophae rhamnoides) on yoghurt biological value and quality

In this research, an integrated physico-chemical and sensory approach was implemented to study the impact of sea buckthorn addition in a fermented dairy product such as yoghurt. Yoghurt samples were prepared with the addition of sea buckthorn puree in different concentrations - 1%, 3%, 5%, 7%. Thus, research was done to determine the impact of the addition of sea buckthorn on the quality of yoghurt. The obtained results demonstrate that fat content is decreasing from 4.43 % for the sample with 1% sea buckthorn to 4.21 % for the sample with 7% sea buckthorn, fact caused by the sea buckthorn addition, which replaces the milk quantity. The protein content for all samples meets the requirements of the regulation for dairy products (min. 1.6%), ranging from 3.29% to 2.6%. During fermentation and storage, the acidity values are increasing and this is most noticeable in samples with the highest sea buckthorn content due to the significant intake of acids from sea buckthorn that speed up the acidification. Following the organoleptic examination, it was deduced that the sample with 5% and 7% added sea buckthorn has favorable characteristics for the consumer, but the latter is to be improved because they have values of over 35% serum release.

Improving the quality of raw milk and yogurt

Milk is a part of many food products. In the expert assessment of the quality of raw materials, primary attention should be paid to its microbiological safety, since poisoning with dairy products is a common cause of diseases of the gastrointestinal tract. The experiment has been carried out on the base in the Teaching and Production Livestock Farm in the Federal State Budgetary Educational Institution of Higher Education “Russian State Agrarian University – Moscow Agricultural Academy named after K. A. Timiryazev” (Moscow). The purpose of the research was to improve the quality indicators of raw milk and yogurt. The method of processing raw milk, which reduces the number of potentially dangerous microorganisms in the products produced from it, has been studied. During the experiment the influence of electromagnetic radiation on organoleptic and physic and chemical parameters has been observed; the quantitative and qualitative composition of milk and yogurt microorganisms has been evaluated. The samples of raw materials had a uniform consistency without sediment and flakes, the color was milky white, and the smell was characteristic of natural cow’s milk. Electromagnetic treatment did not affect the main elements of the chemical composition of milk: the mass fraction of dry substances, fat, protein and lactose. In the experimental samples of raw milk after electromagnetic pulses treatment, the decrease in the growth rate of microorganisms including Quantity of Mesophilic Aerobic and Facultative Anaerobic Microorganisms (QMAFAnM), yeast and mold, has been noted. No bacteria of the Staphylococcus aureus and Escherichia coligroups have been found in the milk samples. The electromagnetic field had the negligible effect on the amount of lactic acid microorganisms in the raw material. During the experiment, there was no negative influence of electromagnetic radiation on the organoleptic, physic and chemical and sanitary-hygienic parameters of yogurt. The issues of ensuring the microbiological safety of raw milk have been described and the method for optimizing the sanitary and hygienic parameters of yogurt in accordance with the current requirements of regulatory documents has been suggest in the article.

Quality of Set Yogurts Made from Raw Milk and Processed Milk Supplemented with Enriched Milk Fat Globule Membrane in a Two-Stage Homogenization Process.

Dairy products are relevant in the food industries as functional ingredients for several food products and contribute towards human nutrition in ameliorating certain disorders. In this study, set yogurts were produced from raw milk and processed milk combined with 4% Lacprodan®PL20 concentration and subjected to two-stage pressure homogenization. The total solids concentration of the mixture was raised to 15% using SMP (skim milk powder). The purpose of this study was to investigate the effect of Lacprodan®PL20 on the set yogurt quality produced by homogenization-induced pressure and its interaction with milk components. The changes in the physical and chemical attributes of the milk fat globule membrane (MFGM) via destabilization of the membrane significantly affected the physicochemical properties of set yogurts produced from processed or raw milk. There was a slight variation in MFGM-specific proteins detected in the set yogurts. Set yogurt produced from homogenized raw milk (HRM) had a considerably higher water-holding capacity, firmness, and apparent viscosity. The microstructure of HRM was dense and compacted, unlike non-homogenized raw milk (NRM) with large MFGM fragments and pore holes between the matrixes. The inclusion of homogenization showed a remarkable improvement in set yogurt quality, promoting interaction between MFGM components and milk proteins.

PENGARUH PENAMBAHAN SARI WORTEL PADA YOGHURT DITINJAU DARI AW, KADAR AIR, VISKOSITAS, TOTAL ASAM TERTITRASI DAN KADAR PROTEIN

Yogurt is a form of beverage product from milk processing that utilizes microbes (Streptococcus thermophillus and Lactobacillus bulgaricus.). In the fermentation process of fresh milk into a semi-solid emulsion product, yogurt also has high nutritional content, one of which is protein. and low in fat. The purpose of this study was to determine the optimal percentage of addition of carrot juice to improve the quality of yogurt in terms of water activity (AW), viscosity, total titrated acid and water content. The ingredients used are cow's milk, carrot juice and plain yogurt starter. Iodine, 75% alcohol and distilled water. The method used in this research is experimental method Comletely Block Design of 5 treatments, namely the addition of carrot juice to yogurt with a concentration of 0%, 10%, 15%, 20%, and 25%. volume of milk (1 liter), with each treatment repeated 4 times. Data analysis used ANOVA (Analysis of Variance), followed by Duncan's Multiple Range Test. The results showed that the addition of carrot juice to yogurt could increase the value of Aw: P0 (0.9) to P4 (0.96), water content: P0 (88.96%) to P4 (92.58%), the total acid value. titration: P0 (0.57%) to P4 (0.67%) and protein content value: P0 (2.97%) to P4 (4.89%), the viscosity value decreased from P0 (216.75) cP) becomes P4 (148.00 cP). Based on the research analysis, it can be concluded that the use of carrot juice with a concentration of 15% gives the best results for yogurt with a value of Aw (0.94), water content (91.21%), viscosity (177.75 cP), total acid titrated (0 , 65%), and protein content (4.26%).

Evaluation of the Effect of Essential Oil Addition on the Quality Parameters and Predicted Shelf Life of Potato Yogurt

Potato, the third most important food crop worldwide, is rich in nutrients but low in protein. In contrast, milk is rich in protein. Yogurt produced through the cofermentation of potatoes and milk is a highly nutritious food. The quality and shelf life of yogurt are important topics in the dairy industry. The objective of this study was to explore the effect of the addition of essential oil (EO) on the shelf life and quality of potato yogurt. The antimicrobial effects of several EOs, the effect of perilla leaf EO (PLEO) concentration on potato yogurt, and the volatile flavor components of PLEO and PLEO potato yogurt were evaluated. The effects of storage time and temperature on the pH, microbial counts, and sensory characteristics of PLEO potato yogurt also were analyzed to establish a shelf-life model. PLEO had an antimicrobial effect and was the appropriate EO for use in the potato yogurt. A total of 69 compounds were detected in PLEO, and limonene was the main compound. PLEO had an effect on the pH, sensory characteristics, and viable bacterial counts of potato yogurt during storage. The optimal concentration of added PLEO was 0.04%. PLEO had considerable influence on volatile flavor components, and the consumer acceptance of 0.04% PLEO potato yogurt was higher than that of potato yogurt without PLEO in the later stage of storage. The shelf life of potato yogurt with PLEO was 6 days longer than that of the control yogurt. PLEO also improved the concentrations of active terpene substances in potato yogurt. The prediction models based on pH and sensory scores at 5°C were established as A = A0e0.00323t and A = A0e0.00355t, respectively. Comparison of the accuracy factor and the deviation factor of the models revealed that the sensory prediction model was more accurate than the pH prediction model. The results of this study provide theoretical and data support for the industrial development of yogurt with EOs, including extension and prediction of its shelf life.