Ocena mikrobiološke varnosti in senzorične kakovosti žitnih izdelkov za zajtrk po preteku roka uporabnosti

Ivanc, Kaja (avtor), Jeršek, Barbka (mentor), Korošec, Mojca (komentor)

Namen raziskave je bil oceniti mikrobiološko varnost in senzorično kakovost desetih različnih žitnih izdelkov za zajtrk po preteku roka minimalne trajnosti. Analizirali smo različne vrste kosmičev, granol, keksov in ovsenih kaš. Analize so bile izvedene v petih časovnih obdobjih: na polovici roka trajanja, ob preteku roka ter 20 %, 40 % in 60 % po preteku roka minimalne trajnosti. Mikrobiološko varnost smo preverjali s kvantitativnimi in kvalitativnimi mikrobiološkimi preiskavami, senzorično kakovost pa z kvalitativno opisno metodo »Označi vse kar ustreza« (CATA) in z ocenjevanjem s sistemom 20 točk. Pri mikrobioloških analizah smo spremljali prisotnost bakterij rodu Salmonella in število koagulaza pozitivnih stafilokokov, bakterije vrst Staphylococcus aureus, Clostridium perfringens, Escherichia coli, Bacillus cereus, skupno število aerobnih mezofilnih bakterij, anaerobnih mezofilnih bakterij, aerobnih sporogenih bakterij, anaerobnih sporogenih bakterij ter plesni in kvasovke. Rezultati so pokazali, da noben od testiranih vzorcev ni presegal mejnih vrednosti za patogene mikroorganizme, kar kaže, da so ti izdelki mikrobiološko varni tudi po preteku roka minimalne trajnosti. Senzorične analize so pokazale, da se kakovost izdelkov s časom shranjevanja manjša. Ovsene kaše so dlje časa po preteku roka minimalne trajnosti ohranjale zadovoljivo senzorično kakovost, medtem ko je pri granolah in prosenih keksih hitreje prišlo do izrazitih sprememb v senzoričnem profilu. Značilne spremembe so bile opazne predvsem pri vonju in aromi. Po preteku roka minimalne trajnosti se je pri izdelkih v različnih časovnih obdobjih pojavil vonj po starem in zatohlem, vonj po kartonu in vonj po žarkem, prisotna je bila tudi žarka aroma in aroma po mokrem kartonu. Izmerjena aktivnost vode (aw) je bila pri vseh vzorcih pod 0,6, kar je pod mejo za rast mikroorganizmov in pojasnjuje stabilno mikrobiološko varnost teh izdelkov. Prav tako se vrednosti pH niso bistveno spreminjale, kar kaže na stabilnost fizikalno-kemijskih lastnosti izdelkov tekom skladiščenja. Raziskava je pokazala da so testirani žitni izdelki mikrobiološko varni tudi po preteku roka minimalne trajnosti, vendar se senzorična kakovost nekaterih izdelkov, zlasti tistih z večjo vsebnostjo maščob in kompleksnejšo sestavo, občutno poslabša.

• Jezik: Slovenski jezik
• Ključne besede: žitni izdelki za zajtrk, mikrobiološka varnost, senzorična kakovost, aw, pH-vrednost, rok minimalne trajnosti
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: BF - Biotehniška fakulteta
• Založnik: [K. Ivanc]
• Leto izida: 2024
• PID: 20.500.12556/RUL-163618
• UDK: 579.67:664.696:543.92
• COBISS.SI-ID: 210852099
• Datum objave v RUL: 09.10.2024

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Assessment of microbiological safety and sensory quality of breakfast cereal products after their shelf life

Izvleček

The aim of the study was to evaluate microbiological safety and sensory quality of ten different breakfast cereal products after the date of minimum durability. We analyzed various types of cereals, granolas, biscuits and oatmeals. The analyses were conducted at five different time points: halfway of the shelf life, at the end of the date od minimum durability and at 20%, 40% and 60% beyond the date od minimum durability. Microbiological safety was assessed by using quantitative and qualitative microbiological tests, while sensory quality was evaluated using the qualitative descriptive »Check-All-That-Apply« (CATA) method and a 20-point scoring system. By microbiological analyses, we monitored the presence of Salmonella spp., and the number of Staphylococcus aureus, Clostridium perfringens, Escherichia coli, Bacillus cereus, total aerobic mesophilic bacteria, anaerobic mesophilic bacteria, aerobic sporogenic bacteria, anaerobic sporogenic bacteria as well as yeasts and moulds. The results indicated that none of the tested samples exceeded the threshold values for pathogenic microorganisms, demonstrating that these products remain microbiologically safe even after the expiration of the minimum shelf life. Sensory analyses showed that the quality of the products changes over time. Oatmeal maintained of acceptable sensory quality for a longer period after the expiration of the minimum shelf life, while granolas and millet biscuits exhibited more pronounced changes in sensory profile more rapidly. Significant changes were primarily observed in odour and aroma. After the date of minimal durability, various off-notes such as stale odor, cardboardy and rancid odour and musty cardboard aroma were detected in different time periods. The measured water activity (aw) in all samples was below 0,6, which is under the treshold for the frowth of microorganisms, explaining the stable microbiological safety of these products. Additionally, the pH-values did not change significantly, indicating the stability of the physicochemical prperties of the products during storage. The study concluded that the the tested breakfast cereal products are microbiologically safe even after theri date of minimum durability. However, the sensory quality of some products, especially those with higher fat content and complex composition, significantly deteriorates.

• Ključne besede: breakfast cereal products, microbiological safety, sensory quality, aw, pH-value, date of minimum durability